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Eukaryotic initiation factor (eIF) 4F plays a central role in the ribosome recruitment phase of cap-dependent translation. This heterotrimeric complex consists of a cap binding subunit (eIF4E), a DEAD-box RNA helicase (eIF4A), and a large bridging protein (eIF4G). In mammalian cells, there are two genes encoding eIF4A (eIF4A1 and eIF4A2) and eIF4G (eIF4G1 and eIF4G3) paralogs that can assemble into eIF4F complexes. To query the essential nature of the eIF4F subunits in normal development, we used CRISPR/Cas9 to generate mouse strains with targeted ablation of each gene encoding the different eIF4F subunits. We find that Eif4e, Eif4g1, and Eif4a1 are essential for viability in the mouse, whereas Eif4g3 and Eif4a2 are not. However, Eif4g3 and Eif4a2 do play essential roles in spermatogenesis. Crossing of these strains to the lymphoma-prone Eμ-Myc mouse model revealed that heterozygosity at the Eif4e or Eif4a1 loci significantly delayed tumor onset. Lastly, tumors derived from Eif4e∆38 fs/+/Eμ-Myc or Eif4a1∆5 fs/+/Eμ-Myc mice show increased sensitivity to the chemotherapeutic agent doxorubicin, in vivo. Our study reveals that eIF4A2 and eIF4G3 play non-essential roles in gene expression regulation during embryogenesis; whereas reductions in eIF4E or eIF4A1 levels are protective against tumor development in a murine Myc-driven lymphoma setting.

Hippuristanol (Hipp) is a natural product that selectively inhibits protein synthesis by targeting eukaryotic initiation factor (eIF) 4A, a DEAD-box RNA helicase required for ribosome recruitment to mRNA templates. Hipp binds to the carboxyl-terminal domain of eIF4A, locks it in a closed conformation, and inhibits its RNA binding. The dependencies of mRNAs for eIF4A during initiation is contingent on the degree of secondary structure within their 5′ leader region. Interest in targeting eIF4A therapeutically in cancer and viral-infected settings stems from the dependencies that certain cellular (e.g. pro-oncogenic, pro-survival) and viral mRNAs show towards eIF4A. Using a CRISPR/Cas9-based variomics screen, we identify functional EIF4A1 Hipp-resistant alleles, which in turn allowed us to link the translation-inhibitory and cytotoxic properties of Hipp to eIF4A1 target engagement. Genome-wide translational profiling in the absence or presence of Hipp were undertaken and our validation studies provided insight into the structure-activity relationships of eIF4A-dependent mRNAs. We find that mRNA 5′ leader length, overall secondary structure and cytosine content are defining features of Hipp-dependent mRNAs.

Eukaryotic cellular mRNAs possess a 5′ cap structure (m7GpppN) which plays a critical role in translation initiation mediated by eukaryotic initiation factor (eIF) 4F. The heterotrimeric eIF4F complex possesses several activities imparted by its subunits that include cap recognition (by eIF4E), RNA unwinding (eIF4A), and factor/ribosome recruitment (eIF4G). Mammalian cells have paralogs of all three eIF4F subunits and it remains an open question as to whether these all can participate in the process of ribosome recruitment. To query the activities of the eIF4F subunits in translation initiation, we adopted an RNA-tethering assay in which select subunits are recruited to a specific address on a reporter mRNA template. We find that all eIF4F subunits can participate in the initiation process. Based on eIF4G:eIF4A structural information, we also designed obligate dimer pairs to probe the activity of all combinations of eIF4G and eIF4A paralogs. We demonstrate that both eIF4GI and eIF4GII can associate with either eIF4A1 or eIF4A2 to recruit ribosomes to mRNA templates. In combination with eIF4E and eIF4E3, our results indicate the presence of up to eight eIF4F complexes that can operate in translation initiation.

Melanomas display poor response rates to adjuvant therapies because of their intrinsic resistance to proapoptotic stimuli. This study indicates that such resistance can be overcome, at least partly, through the targeting of eEF1A elongation factor with narciclasine, an Amaryllidaceae isocarbostyril controlling plant growth. Narciclasine displays IC50 growth inhibitory values between 30–100 nM in melanoma cell lines, irrespective of their levels of resistance to proapoptotic stimuli. Normal noncancerous cell lines are much less affected. At nontoxic doses, narciclasine also significantly improves (P=0.004) the survival of mice bearing metastatic apoptosis-resistant melanoma xenografts in their brain. The eEF1A targeting with narciclasine (50 nM) leads to 1) marked actin cytoskeleton disorganization, resulting in cytokinesis impairment, and 2) protein synthesis impairment (elongation and initiation steps), whereas apoptosis is induced at higher doses only (≥200 nM). In addition to molecular docking validation and identification of potential binding sites, we biochemically confirmed that narciclasine directly binds to human recombinant and yeast-purified eEF1A in a nanomolar range, but not to actin or elongation factor 2, and that 5 nM narciclasine is sufficient to impair eEF1A-related actin bundling activity. eEF1A is thus a potential target to combat melanomas regardless of their apoptosis-sensitivity, and this finding reconciles the pleiotropic cytostatic of narciclasine.—Van Goietsenoven, G., Hutton, J., Becker, J.-P., Lallemand, B., Robert, F., Lefranc, F., Pirker, C., Vandenbussche, G., Van Antwerpen, P., Evidente, A., Berger, W., Prévost, M., Pelletier, J., Kiss, R., Goss Kinzy, T., Kornienko, A., Mathieu, V. Targeting of eEF1A with Amaryllidaceae isocarbostyrils as a strategy to combat melanomas.

Levels of eukaryotic initiation factor 4E (eIF4E) are frequently elevated in human cancers and in some instances have been associated with poor prognosis and outcome. Here we utilize transgenic and allograft breast cancer models to demonstrate that increased mammalian target of rapamycin (mTOR) signalling can be a significant contributor to breast cancer progression in vivo. Suppressing mTOR activity, as well as levels and activity of the downstream translation regulators, eIF4E and eIF4A, delayed breast cancer progression, onset of associated pulmonary metastasis in vivo and breast cancer cell invasion and migration in vitro. Translation of vascular endothelial growth factor (VEGF), matrix metallopeptidase 9 (MMP9) and cyclin D1 mRNAs, which encode products associated with the metastatic phenotype, is inhibited upon eIF4E suppression. Our results indicate that the mTOR/eIF4F axis is an important contributor to tumor maintenance and progression programs in breast cancer. Targeting this pathway may be of therapeutic benefit.

Cycloheximide and congeners as inhibitors of eukaryotic protein synthesis from endophytic actinomycetes Streptomyces sps. YIM56132 and YIM56141

The 5' RNA cap structure (m7GpppRNA) is a key feature of eukaryotic mRNAs with important roles in stability, splicing, polyadenylation, mRNA export, and translation. Higher eukaryotes can further modify this minimal cap structure with the addition of a methyl group on the ribose 2'-O position of the first transcribed nucleotide (m7GpppNmpRNA) and sometimes on the adjoining nucleotide (m7GpppNmpNmpRNA). In higher eukaryotes, the DXO protein was previously shown to be responsible for both decapping and degradation of RNA transcripts harboring aberrant 5’ ends such as pRNA, pppRNA, GpppRNA, and surprisingly, m7GpppRNA. It was proposed that the interaction of the cap binding complex with the methylated cap would prevent degradation of m7GpppRNAs by DXO. However, the critical role of the 2’-O-methylation found in higher eukaryotic cap structures was not previously addressed. In the present study, we demonstrate that DXO possesses both decapping and exoribonuclease activities toward incompletely capped RNAs, only sparing RNAs with a 2’-O-methylated cap structure. Fluorescence spectroscopy assays also revealed that the presence of the 2’-O-methylation on the cap structure drastically reduces the affinity of DXO for RNA. Moreover, immunofluorescence and structure-function assays also revealed that a nuclear localisation signal is located in the amino-terminus region of DXO. Overall, these results are consistent with a quality control mechanism in which DXO degrades incompletely capped RNAs.

Cytoplasmic stress granules (SGs) are specialized regulatory sites of mRNA translation that form under different stress conditions known to inhibit translation initiation. The formation of SG occurs via two pathways; the eukaryotic initiation factor (eIF) 2α phosphorylation-dependent pathway mediated by stress and the eIF2α phosphorylation-independent pathway mediated by inactivation of the translation initiation factors eIF4A and eIF4G. In this study, we investigated the effects of targeting different translation initiation factors and steps in SG formation in HeLa cells. By depleting eIF2α, we demonstrate that reduced levels of the eIF2.GTP.Met-tRNAiMet ternary translation initiation complexes is sufficient to induce SGs. Likewise, reduced levels of eIF4B, eIF4H, or polyA-binding protein, also trigger SG formation. In contrast, depletion of the cap-binding protein eIF4E or preventing its assembly into eIF4F results in modest SG formation. Intriguingly, interfering with the last step of translation initiation by blocking the recruitment of 60S ribosome either with 2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamideis or through depletion of the large ribosomal subunits protein L28 does not induce SG assembly. Our study identifies translation initiation steps and factors involved in SG formation as well as those that can be targeted without induction of SGs.

2',3'-Cyclic nucleotide 3'-phosphodiesterase (CNP) is one of the earliest myelin-related proteins to be specifically expressed in differentiating oligodendrocytes (ODCs) in the central nervous system (CNS) and is implicated in myelin biogenesis. CNP possesses an in vitro enzymatic activity, whose in vivo relevance remains to be defined, because substrates with 2',3,-cyclic termini have not yet been identified. To characterize CNP function better, we previously determined the structure of the CNP catalytic domain by NMR. Interestingly, the structure is remarkably similar to the plant cyclic nucleotide phosphodiesterase (CPDase) from A. thaliana and the bacterial 2'-5' RNA ligase from T. thermophilus, which are known to play roles in RNA metabolism. Here we show that CNP is an RNA-binding protein. Furthermore, by using precipitation analyses, we demonstrate that CNP associates with poly(A)(+) mRNAs in vivo and suppresses translation in vitro in a dose-dependent manner. With SELEX, we isolated RNA aptamers that can suppress the inhibitory effect of CNP on translation. We also demonstrate that CNP1 can bridge an association between tubulin and RNA. These results suggest that CNP1 may regulate expression of mRNAs in ODCs of the CNS.

The synthesis of oligonucleotides containing 2′-deoxy-2′-fluoro-4′-thioarabinonucleotides is described. 2′-Deoxy-2′-fluoro-5-methyl-4′-thioarabinouridine (4′S-FMAU) was incorporated into 18-mer antisense oligonucleotides (AONs). 4′S-FMAU adopts a predominantly northern sugar conformation. Oligonucleotides containing 4′S-FMAU, unlike those containing FMAU, were unable to elicit E. coli or human RNase H activity, thus corroborating the hypothesis that RNase H prefers duplexes containing oligonucleotides that can adopt eastern conformations in the antisense strand. The duplex structure and stability of these oligonucleotides was also investigated via circular dichroism (CD)- and UV- binding studies. Replacement of the 4′-oxygen by a sulfur atom resulted in a marked decrease in melting temperature of AON:RNA as well as AON:DNA duplexes. 2′-Deoxy-2′-fluoro-4′-thioarabinouridine (4′S-FAU) was incorporated into 21-mer small interfering RNA (siRNA) and the resulting siRNA molecules were able to trigger RNA interference with good efficiency. Positional effects were explored, and synergy with 2′F-ANA, which has been previously established as a functional siRNA modification, was demonstrated.

Lissoclimides are cytotoxic compounds produced by shell-less molluscs through chemical secretions to deter predators. Chlorinated lissoclimides were identified as the active component of a marine extract from Pleurobranchus forskalii found during a high-throughput screening campaign to characterize new protein synthesis inhibitors. It was demonstrated that these compounds inhibit protein synthesis in vitro, in extracts prepared from mammalian and plant cells, as well as in vivo against mammalian cells. Our results suggest that they block translation elongation by inhibiting translocation, leading to an accumulation of ribosomes on mRNA. These data provide a rationale for the cytotoxic nature of this class of small molecule natural products.

The [Mo 5 O 13 (OMe) 4 (NO)] 3− anion either as a mixed Na + / n -Bu 4 N + or Na + /Me 4 N + salt reacts with [Cp*RhCl 2 ] 2 after partial or total elimination of chloride in methanol and, sometimes, subsequent addition of bromide, to form [{Cp*Rh(H 2 O)}Mo 5 O 13 (OMe) 4 (NO)] − isolated as a n -Bu 4 N + or Me 4 N + salt, and [{(Cp*Rh) 2 (μ-X)}Mo 5 O 13 (OMe) 4 (NO)] (X=Cl or Br). The low-temperature rhodium K-edge extended X-ray absorption fine structure (EXAFS) data for ( n -Bu 4 N)[{Cp*Rh(H 2 O)}Mo 5 O 13 (OMe) 4 (NO)] and [{(Cp*Rh) 2 (μ-Cl)}Mo 5 O 13 (OMe) 4 (NO)] have been fitted by five- and seven-shell models, respectively, and agree well with X-ray crystallographic data for (Me 4 N)[{Cp*Rh(H 2 O)}Mo 5 O 13 (OMe) 4 (NO)]·2H 2 O and [{(Cp*Rh) 2 (μ-Br)}Mo 5 O 13 (OMe) 4 (NO)]·CH 2 Cl 2 . These compounds can serve as structural models for the elucidation of the bonding mode of Cp*Rh fragments in other polyoxoanion-supported rhodium(III) complexes. In that way, another compound which could not be analyzed by X-ray diffraction has been identified as an adduct of ( n -Bu 4 N) 2 [{Na(MeOH)}Mo 5 O 13 (OMe) 4 (NO)] with [{(Cp*Rh) 2 (μ-Cl)}Mo 5 O 13 (OMe) 4 (NO)] on the basis of EXAFS data.

Reaction of [W2(μ-COH)Cp2(CO)2(μ-dppm)]BF4 (Cp = η5-C5H5; dppm = Ph2PCH2PPh2) with CH2N2 in the presence of CuCl at −75 °C leads to the methoxycarbyne cluster [CuW2Cl(μ3-COMe)Cp2(CO)2(μ-dppm)]BF4. Copper(I) chloride can be cleanly removed from the latter upon addition of PPh3, thus giving the methoxycarbyne complex [W2(μ-COMe)Cp2(CO)2(μ-dppm)]BF4. In the absence of CuCl, either the hydroxy or the methoxycarbyne ditungsten cations react with CH2N2 to give a mixture of the μ-methylene, μ-alkenyl compound [W2(μ-CH2){μ-η1:η2-C(OMe)CH2}Cp2(CO)2(μ-dppm)]BF4, which has been characterized through an X-ray study, and the μ-alkyne, μ-alkenyl species [W2{μ-η1:η2-C(OMe)CH}{μ-η1:η2-C(OMe)CH2}Cp2(CO)(μ-dppm)]BF4, the latter being the result of the addition of four molecules of CH2N2 to the starting hydroxycarbyne compound. The influence of experimental conditions on the above reactions has been analyzed through separate experiments. For example, the use of tetrahydrofuran as solvent almost suppresses the formation of t...

Molybdenum complexes containing mixed disubstituted organohydrazido(1−) and organohydrazido(2−) ligands, [Mo(NHNPhR)(NNPhR)(acac)Cl 2 ], R = Ph ( I ), R = Me ( II ), react in acetonitrile with sodium hydridotris(pyrazolyl)borate, NaTp, or in toluene with potassium hydridotris (3,5-dimethylpyrazolyl) borate, KTp * , to afford the neutral six-coordinated species formulated as [TpMo(NNPhR) 2 Cl], R = Ph ( III ), R = Me ( IV ) and [Tp*Mo(NNPhR) 2 Cl], R = Ph ( V ), R = Me ( VI ). These compounds have been characterized by elemental analysis, by IR, UV-visible, 1 H and 13 C NMR spectroscopy, and by mass spectrometry. The electrochemical behavior of complexes III–VI has also been studied by cyclic voltammetry. The X-ray crystal structure of IV has been determined. Crystals are parallelepiped, space group Pbnm , with a = 7.468(2), b = 18.483(3), c = 19.052(3) A, α = β = γ = 90° and Z = 4. The structure was solved and refined by full-matrix, least-squares methods to R and R w , values of 0.038 and 0.049, respectively. The complex displays a distorted octahedral geometry with symmetrical organohydrazido(2−) ligands adopting the nearly linear mode (Mo-N-N = 169.4(3)°). This linearity and the short bond distances (Mo-N = 1.771(4), N-N = 1.308(5) A) indicate an extensive π -electronic delocalization throughout the Mo-N-N fragment.

Reaction of [1,1′-isopropylidene-3,3′-di-tert.butyl-bis(η5-cyclopentadienide)] dilithium with TiCl3, followed by treatment with HCl, and ZrCl4 in various solvent mixtures in the temperature range 0–50°C gives corresponding ansa-metallocene dichlorides as mixtures of the anti/syn-isomers, 1:1. The crystal and molecular structures of three of the four isomers were determined, i.e. rac(anti)-[1,1′-isopropylidene-3,3′-di-tert.butyl-bis(η5-cyclopentadienyl)]TiCl2, space group B2/b, rac(anti)-[1,1′-isopropylidene-3,3′-di-tert.butyl-bis(η5-cyclopentadienyl)]ZrCl2, space group P212121, and meso(syn)-1,1′-[isopropylidene-3,3′-di-tert.butyl-bis(η5-cyclopentadienyl)]ZrCl2, space group P21/n.

Reaction of either (n-Bu4N)2[Mo5O13(OMe)4(NO){Na(MeOH)}]·xMeOH or (n-Bu4N)3[Mo6O18(NO)] with various reducing agents, including N2H4·2HCl, in methanol or in a mixture of methanol and acetonitrile, yields reduced nitrosyl decamolybdates, among which (n-Bu4N)[Mo10O25(OMe)6(NO)] ((n-Bu4N)II) and two forms of (n-Bu4N)2[Mo10O24(OMe)7(NO)] ((n-Bu4N)2IVa and (n-Bu4N)2IVb) have been crystallographically characterized. IVa,b are diastereoisomers that differ in the location of methoxo groups. The molecular structures of II and IV are closely related to that of [W10O32]4-, the so-called decatungstate Y, and consist of two halves of five edge-sharing octahedra connected through four quasi-linear Mo−O−Mo bridges. Besides the four electrons essentially residing at the Mo(II) center bearing the nitrosyl ligand, II and IV further accommodate two and four delocalized “blue” electrons, respectively. II and IV thus contain molybdenum atoms in three different oxidation states, Mo(II), Mo(V), and Mo(VI). On the basis of their...

The crystal structures of three compounds have been determined at room temperature, namely [Gd(hfa)3Cu(salen)] (1), [Y(hfa)3Cu(salen)] (2), and [Gd(hfa)3Cu(salen)(Meim)] (3), and the crystal structure of a fourth compound, [La(hfa)3(H2O)Cu(salen)] (4), has been determined at −100 °C; hfa = hexafluoroacetylacetonato, salen = N,N‘-ethylenebis(salicylideneaminato), and Meim = 1-methylimidazole. [La(hfa)3Ni(salen)] (5), isomorphous with 1, has also been synthesized. 1 crystallizes in the monoclinic system, space group P21/n, with a = 17.292(5) A, b = 22.370(5) A, c = 19.658(6) A, β = 90.07(2)°, and Z = 8. 2 crystallizes in the triclinic system, space group P1, with a = 12.207(3) A, b = 13.019() A, c = 13.011(6) A, α = 82.87(4)°, β = 83.55(3)°, γ = 70.91(3)°, Z = 2. 3 crystallizes in the monoclinic system, space group P21/n, with a = 16.521(9) A, b = 20.381(5) A, c = 12.758(6)°, β = 93.22(6)°, and Z = 4. 4 crystallizes in the monoclinic system, space group P21/n, with a = 12.826(2) A, b = 23.067(8) A, c = 13....

A new Cu–Zn bimetallic precursor Cu 0.06 Zn 0.94 C 4 O 4 H 2 ·2H 2 O useful as a model catalyst for methanolation of syngas was prepared and identified. It crystallises in the monoclinic space group Cc with cell parameters a = 5.725(1), b = 16.251(2), c = 6.825(1) A, β = 90.72(1)°, Z = 4. The structure analysis shows a two-dimensional polymeric structure with layers containing metal atoms interconnected by tridentate maleate anions. The smallest ring in the layer contains 18 atoms among which are three metal atoms. These metal atoms are connected by two maleate ligands through the opposite carboxylic groups and the ring is completed by one syn-anti carboxylate bridge Zn–O–C–O–Zn. The metal atom is five-co-ordinated in the MO 2 O 3 form through three oxygen atoms from three different maleate anions and two terminal water ligands. The packing of the structure is stabilised by intra- and inter-layer hydrogen bonds. Thermal decomposition begins with dehydration (75–170 °C) followed by decomposition of the maleate anions (190–635 °C). As final phases, zincite ZnO (major) and tenorite CuO (minor) were identified.

The reactions of 2-thienylamidoxime and 2-thienylmethylamidoxime with [MoO2(acae)2] or x-(NBu4 [Mo8O26]. in alcohols or acetonitrile, yield a number of compounds with different nuclearities and various molybdenum cores, such as the compact {Mo4O10(OMe)2}2+ the cyclic {Mo4O12}, and the open {Mo11On211-1}2+ (n= 2 or 4) cores. Addition of NH2OH to the reaction mixtures results in the formation of nitrosyl complexes containing either the Mo(NO)3 or the Mo(NO)22 units. The amidoxime component may be present either as RC(NH2)NHO. RC(NHi2), RC(NH)NHO or RC(NH)NO2: ligands, or as hydrogen-bonded RC(NH2)NOH molecules. The crystal structures of [MoO(acac)RIC'(NH2)NO] {RJC(NH)NO}](1), [Mo(NO)(acae)2 {RIC(NH2)NO}] (4), (NBu4)2[Mo4O10(OMe)2{RIC(NH) NO}2] (12a),(NBu4)2(H3O)[Mo5O13(OMe)4(NO)].2R1C(NH2)NOH(13b) and [R1C(NH2)2)]3[Mo5O13(OEt)4(NO)] (14) (R1=2-thienyl) are reported. The cryslallographic data for these compounds are as follows:1, mono-clinic. P21 a.a=24.547(4)A. b=8.188(4)A. c=9.607(3)A, s=96.18(3)c, R=0.046. R10=0.050: 4. monoclinic, P21c.a=8.265(2)A, b=9.381(2)A,c=24.770(4)A, c = 24.7701(4) A, s=93.99(2). R=0.039. R=0.042;12a, monoclinic, C2/c, a= 19.570(5)A. b=16.883(4)A, c = 19.82(l)A. s= 114.36(5)°, R=0.064,R.=0.074;13b monoclinic;. P21 c.a=18.197(5)A, b=15.857(14) A, c = 23.075(17) A, β=93.20(3). R=O.050. Rw=0.057;14, trictinic PI, a = 9.871(3),b= 14.138(3).c= 14.781(8)A. α=92.67(2)c β=99.36(1)° γ=90.52(2)°. R = 0.044. Rw = 0.049. Particular attention is focused on the various coordination modes that the different ligand forms adopt: µ- κO, κ2N,O, κ2N',O, µ-κN: κ2O. and μ3- κN:κN:κ2O.

The recruitment of ribosomes to eukaryotic cellular mRNAs requires the activity of two prototypic RNA helicases, eukaryotic initiation factor (eIF) 4AI and eIF4AII. The eIF4A isoforms are highly conserved, are thought to be functionally interchangeable, and are directed to the 5′ m7GpppN cap structure of mRNAs during translation initiation by virtue of their assembly into eIF4F, a heterotrimeric complex that also harbors the eIF4E cap binding protein and eIF4G scaffolding unit. During the course of RNA interference experiments aimed at investigating the respective roles of eIF4AI and eIF4AII in translation, we uncovered a cellular response pathway whereby suppression of eIF4AI increases transcription of the eIF4AII gene, leading to elevated eIF4AII mRNA and protein levels. Inhibition of eIF4AI suppresses protein synthesis, and although eIF4AII protein levels increase above and beyond what should be sufficient to compensate for the decrease in eIF4AI levels, there is no corresponding rescue of translation or of the block on cellular proliferation that occurs upon eIF4AI suppression. These results were phenocopied using the small molecule eIF4A inhibitor hippuristanol. Taken together, our results indicate that eIF4AI and eIF4AII expression appear linked and that the two protein isoforms exhibit functional differences.

By reaction of the unsymmetrical alkylthioalkynes RCSC2H5 (R = CH3 or C6H5) with iron carbonyl, the classical dinuclear compound [Fe2(CO)6L], where L results from the coupling of two alkynes, is obtained. This compound, which contains a ferrole moiety, has a characteristic feature: a carbon-sulfur bond can be cleaved easily. This may be either the bond linking sulfur to the ferrole part if SC2H5 is at the α position with respect to iron, or the bond linking sulfur to the ethyl group if SC2H5 is at the β position with respect to iron. Utilizing these cleavages, trinuclear, tetranuclear, and pentanuclear iron clusters were prepared. Fifteen compounds corresponding to seven types of structure are described, using NMR and X-ray diffraction. Trinuclear compounds are based on an open triangle of iron atoms. Tetranuclear compounds have an iron skeleton which is either T-shaped, or planar, or made of two separate dinuclear units. The pentanuclear skeleton is composed of a triangle and a quadrangle sharing an edge.

Both [Mo6O18(NPh)]2− and [Mo6O17(NPh)2]2− species are formed by reaction of (n-Bu4N)2[Mo6O19] with either 1 or 2 equiv. of Ph3PNPh in pyridine or acetonitrile and have been isolated as mixtures. Single-crystal X-ray diffraction analyses have shown that [Mo6O18(NPh)]2−, [Mo6O17(NPh)2]2− and [Mo6O19]2− can be found together in the same crystal of average composition (n-Bu4N)2[Mo6O19−x(NPh)x]. The structural parameters of the averaged anions have been determined for x=1.16 (sample 1) and x=0.92 (sample 2). Crystal data for 1: a=12.684(4), b=22.750(4), c=19.483(3) A, β=103.04(2)°, space group P21/c, Z=4, R=0.048 and Rw=0.051 for 3846 reflections with I⩾3σ(I). Crystal data for 2: a = 12.678(2), b=22.645(3), c=19.462(4) A, β=104.16(2)°, space group P21/c, Z=4, R=0.058 and Rw=0.061 for 5243 reflections with I⩾3σ(I). The products have been studied in acetonitrile solution by 95Mo and 14N NMR spectroscopy, Raman spectrophotometry and electrochemistry. Each of these techniques has confirmed the presence of the mono- and bis-imido derivatives together with the parent species, and has allowed both the characteristics of the individual components and the composition of the solution to be determined; the results obtained by the different methods are in reasonable agreement.

2,4-Dimethyl-3-phenyl-[2′-methyl-3′chloro]-7-chloro-8-methyl-2,4-dibora-1,3-diazaronaphthalene (C 16 H 18 B 2 N 2 Cl 2 ) crystallizes in the monoclinic system: P 2/a ; a = 8.149(3) A, b = 13.379(3) A and c = 15.193(3) A; β = 91.03(2)°; Z = 4; R = 0.043; R w = 0.041. Reaction with [Cr(CO) 6 ] gives exclusively the compounds with Cr(CO) 3 η 6 -bonded to the benzo part of the molecule. This derivative is a 1:1 mixture of atropisomers which were partially separated and whose configurations could be deduced by means of solvent effects in nuclear magnetic resonance (NMR) spectroscopy. Similar results were obtained with 2,4-dimethyl-3-phenyl-[2t - methyl-4′-chloro]-6-chloro-8-methyl-2,4-dibora-1,3-diazaronaphthalene and [Cr(CO) 6 ] although the separation of isomers failed. Additionally, two closely related η 6 -bonded isomers originating from the above ligands were identified in which the chlorine atom was replaced by a hydrogen atom. All these compounds were thoroughly characterized by high resolution 1 H and 13 C one-dimensional and 1 H- 1 H nuclear Overhauser spectroscopy (NOESY) and correlated two-dimensional NMR spectroscopy (COSY). Further, the reaction of [Cr(CO) 6 ] with B , B′ , B″ -trimethyl- N , N′ , N′ -triarylborazine, the phenyl bearing a para substituent (H, F or Me), was shown by 1 H and 13 C NMR spectroscopy to yield a compound with one phenyl group η 6 bonded to Cr(CO) 3 .

The reaction of Cp[sub 2]MMe[sub 2](M = Zr, Hf) with Ph[sub 2]Si(OH)[sub 2] yields the eight-membered ring [Cp[sub 2]M([mu]-OSiPh[sub 2]O)][sub 2] (m = Zr (1), Hf (2)). 1 crystallizes in the space group P[bar 1] with a = 10.410(9) [angstrom], b = 12.140(6) [angstrom], c = 16.318(5) [angstrom], [alpha] = 94.36(3)[degrees], [beta] = 103.42(5)[degrees], [gamma] = 93.16(6)[degrees], and Z = 2. The crystal structure reveals that the ring is not planar. The Cp[sub 2]Zr units are bent 20[degrees] out of the Si[sub 2]O[sub 4] plane to give a [open quotes]chaise longue[close quotes] conformation; however, in solution the molecule is fluxional on the NMR time scale. The zirconium-oxygen distances of 1.974(2) and 1.983(2) [angstrom] are significantly longer than those reported in other Zr-O-Si compounds. EHMO calculations suggest that the Zr-O bond order may be rationalized in terms of an in-plane [pi]-system.

In acetonitrile, bis(acetylacetonato)dioxomolybdenum(VI), [MoO 2 (acac) 2 ], reacts with disubstituted hydrazine hydrohalides (RR'NNH 3 + X - : R=R'=Ph; R=Ph, R'= Me; X=Cl, Br, I) to yield a new series of complexes, which have been characterized by elemental analysis, electrochemistry and spectroscopy (IR, UV-visible, and 1 H NMR) and formulated as [Mo(NHNPh 2 )(NNPh 2 )(acac)X 2 ] (X=Cl, Br, I) and [Mo(NHNMePh)-(NNMePh)(acac)X 2 ] (X=Cl, Br, I)

Reinvestigation of the reaction of 2, 3-butanedione with ethanolamine afforded the known cis-4a, 8a-dimethyl[1,41-oxazino-[3,2-b][1,4]oxazine as well as two new tricyclic products: 12, 13-di-methyl-2, 7-dioxa-5, 10-diaza-tricycle[4, 4, 4, 01,6]trans-tetradecan-12-13-diol, and N,N'-[(4″,5″-dimethyl) 1″, 2″-phenylene]-2,2′-dimethyl-bisoxazolidine as established by X-ray analysis.

Cycloheximide and congeners as inhibitors of eukaryotic protein synthesis from endophytic actinomycetes Streptomyces sps. YIM56132 and YIM56141

Reaction of (n-B 4 N) 3 [Mo 6 O 18 (NP)] (1) with dimethyl sulfate in methanol gives (n-B 4 N) 2 [SMo 12 O 40 ] and (n-Bu 4 N) 2 [Mo 6 O 17 (OCH 3 )(NO)] (2). Compound 2 has been characterized by X-ray diffraction. Crystal data for 2: monoclinic space group P2 1 /c, a=9.514(3) A, b=18.066(5) A, c=15.418(4) A, β=105.25(2) o , Z=2; 2451 reflections, R=0.037. The anion [Mo 6 O 17 (OCH 3 )(NO)] 2- is structurally related to [Mo 6 O 18 (NO)] 3- and to [Mo 6 O 19 ] 2- ; however, due to its location on an inversion center, structural porameters for only a disorder-averaged anion were obtained

Reactions of hydroxylamine with isopolyoxomolybdates in methanol or ethanol yield nitrosylpolyoxomolybdates of the type [Mo 5 O 13 (OR) 4 (NO)] 3- (R=Me, Et). The structures of (n-Bu 4 N) 2 [Mo 5 O 13 (OMe) 4 (NO){Na(MeOH)}].3MeOH, K 2 [Mo 5 O 13 (OMe) 4 (NO){Na(H 2 O)(MeOH)}], (Me 4 N) 2 [Mo 5 O 13 (OMe) 4 (NO){Na-(H 2 O)}], and (n-Bu 4 N) 4 [Mo 5 O 13 (OMe) 4 (NO)(Na(DMF)}] have been determined by X-ray cryatallography

Neodymium trichloride reacts with 2 equiv. of the lithium salt of 9-(cyclopentadienyl-1-methylethyl)-9,10-dihydroanthracene in THF to give the “ate” complex [Li(THF)4][Nd{(C5H4)CMe2 (C14H10)}2] which has been characterized by its crystal structure and elemental analysis. The neodymium atom is situated in tetrahedral environment. It is η5-bonded to the two cyclopentadienyl rings and σ-bonded to the C(10) atoms of the two dihydroanthracene moieties.

Iodocyclization of O -tributylstannyl- d -glucal with iodine in acetonitrile gave 1,6-anhydro-2-deoxy-2-iodo-β- d -glucopyranose ( 1 ) in high yield. The 3,4-di- O -acetyl derivative of 1 could be converted into the corresponding 2-deoxy compound and into the 2- C -allyl-2-deoxy branched sugar ( 5 ) by treatment with tributylstannane and allyltributylstannane, respectively. Controlled alkaline hydrolysis of 5 gave the 4-monoacetyl derivative. Complete hydrolysis of 5 gave the 3,4-diol, which underwent a 5- exo cyclization by treatment with N -bromosuccinimide. 1 H NMR spectroscopy and X-ray analysis showed that the cyclized product has the B 3,O conformation in its pyranose ring, which is trans -fused to the newly formed tetrahydrofuran ring.

A di-μ 3 -carbyne cluster [Fe 3 (CO) 9 {μ 3 -CN(CH 3 ) 2 }(μ 3 -CC 2 H 5 )] has been synthesized by reaction of [Fe 2 (CO) 9 ] with the alkynylethyl sulphide C 2 H 5 SCCCH 3 and trimethylamine oxide at 69°C. One of the μ 3 -carbyne functions resulted from the rare activation of the three CH bonds of a trimethylamine methyl group.

The ansamycins are a diverse and often physiologically active group of compounds that include geldanamycin and rifamycin, inhibitors of heat shock protein 90 and prokaryotic DNA-dependent RNA synthesis, respectively. Cytotrienin A is an ansamycin-type small molecule with potent antiproliferative and proapoptotic properties. Here, we report that this compound inhibits eukaryotic protein synthesis by targeting translation elongation and interfering with eukaryotic elongation factor 1A function. We also find that cytotrienin A prevents HUVEC tube formation and diminishes microvessel formation in the chorioallantoic membrane assay. These results provide a molecular understanding into cytotrienin A's previously reported properties as an anticancer apoptosis-inducing drug.

We report that combining a DNA analog (2?F-ANA) with rigid RNA analogs [2?F-RNA and/or locked nucleic acid (LNA)] in siRNA duplexes can produce gene silencing agents with enhanced potency. The favored conformations of these two analogs are different, and combining them in a 1–1 pattern led to reduced affinity, whereas alternating short continuous regions of individual modifications increased affinity relative to an RNA:RNA duplex. Thus, the binding affinity at key regions of the siRNA duplex could be tuned by changing the pattern of incorporation of DNA-like and RNA-like nucleotides. These heavily or fully modified duplexes are active against a range of mRNA targets. Effective patterns of modification were chosen based on screens using two sequences targeting firefly luciferase. We then applied the most effective duplex designs to the knockdown of the eIF4E binding proteins 4E-BP1 and 4E-BP2. We identified modified duplexes with potency comparable to native siRNA. Modified duplexes showed dramatically enhanced stability to serum nucleases, and were characterized by circular dichroism and thermal denaturation studies. Chemical modification significantly reduced the immunostimulatory properties of these siRNAs in human peripheral blood mononuclear cells.

Thiometallates MS 4 2− (M  Mo, W) form with copper(I) heterobimetallic complexes which are interesting because of the versatility of the structural types obtained. The various structures obtained by addition of copper(I) to MS 4 2− are described and illustrated by examples recently reported in the literature. The synthesis and structural characterization of (NPr 4 ) 3 [MS 4 Cu 4 Cl 5 ] are given together with the connections which exist between ‘open’ and ‘closed’ cubane structures.

1-Methyl-1-phenylhydrazine reacts with [MoO2(acac)2] in ROH (R = Me, Et, n-Pr) at room temperature, to yield [MoO(NNMePh)(acac)2] (I). In refluxing ROH under argon, complex I transforms into [{MoO(NNMePh)(acac)(μ-OR)}2] (R = Me(II), Et(III), n-Pr(IV)). The crystal structures of I and IV are reported. Crystals of I are monoclinic, space group P21/c, with unit cell dimensions a = 8.442(1), b = 16.090(1), c = 13.875(1) A, β = 94,86(1)° and Z = 4. The structure was solved using 2529 unique observed reflections. The refinement of 226 variables gave R and Rw values of 0.024 and 0.026, respectively. The lattice is made of discrete mononuclear molecules. Crystals of IV are monoclinic, space group P21/n, with a = 8.917(2), b = 21.728(3), c = 9.351(1) A, β = 107.83(2)° and Z = 2. The final refinement of 200 variables gave R = 0.036 and Rw = 0.039 for 2700 observed reflections. The lattice is made of discrete centrosymmetric dinuclear molecules. The geometries of the cis-[MoO(NNMePh)]2+ cores in I and IV are similar and indicative of multiple bonding. In I, MoO = 1.701(2), MoN = 1.789(3), NN = 1.281(4) A, MoNN = 175.6(2), OMoN = 102.8(1)°; in IV, MoO = 1.693(3), MoN = 1.780(4), NN = 1.292(6) A, OMoN = 101.8(2)°.

The syntheses of several novel bis(aryldiazenido)molybdenum complexes of the type [Mo(NNC6H4R-p)2(aet)2] (aet = aminoethanethiolate, NH2CH2CH2S−; R = H, Me, OMe, F or NO2), from [MoO2(aet)2] and the appropriate p-substituted phenylhydrazine, are described. These compounds have been characterized by conventional spectroscopic methods. The crystal structure of [Mo(NNC6H4Me-p)2(aet)2] has been determined by X-ray diffraction. The molecule has C2 crystallographic symmetry. The tolyldiazenido groups exhibit the singly-bent geometry: MoNN = 171.7(2)°, NNC = 118.4(2)°, MoN = 1.826(2) A, NN = 1.229(3) A.

BACKGROUND: The process of translation occurs at a nexus point downstream of a number of signal pathways and developmental processes. Modeling activation of the PTEN/AKT/mTOR pathway in the Emu-Myc mouse is a valuable tool to study tumor genotype/chemosensitivity relationships in vivo. In this model, blocking translation initiation with silvestrol, an inhibitor of the ribosome recruitment step has been showed to modulate the sensitivity of the tumors to the effect of standard chemotherapy. However, inhibitors of translation elongation have been tested as potential anti-cancer therapeutic agents in vitro, but have not been extensively tested in genetically well-defined mouse tumor models or for potential synergy with standard of care agents. METHODOLOGY/PRINCIPAL FINDINGS: Here, we chose four structurally different chemical inhibitors of translation elongation: homoharringtonine, bruceantin, didemnin B and cycloheximide, and tested their ability to alter the chemoresistance of Emu-myc lymphomas harbouring lesions in Pten, Tsc2, Bcl-2, or eIF4E. We show that in some genetic settings, translation elongation inhibitors are able to synergize with doxorubicin by reinstating an apoptotic program in tumor cells. We attribute this effect to a reduction in levels of pro-oncogenic or pro-survival proteins having short half-lives, like Mcl-1, cyclin D1 or c-Myc. Using lymphomas cells grown ex vivo we reproduced the synergy observed in mice between chemotherapy and elongation inhibition and show that this is reversed by blocking protein degradation with a proteasome inhibitor. CONCLUSION/SIGNIFICANCE: Our results indicate that depleting short-lived pro-survival factors by inhibiting their synthesis could achieve a therapeutic response in tumors harboring PTEN/AKT/mTOR pathway mutations.

Nucleophilic substitutions in the double cubane-like structures [MS4(CuCl)5Cl2]4− (M=Mo, W) are complicated by elimination reactions. With NCS− an edge-elimination process gave the [MS4(CuNCS)4]2− anion whereas a face-elimination by PPh3 led to the monocubane structure [MS4(CuPPh3)4Cl]. Substitution by bipyridine produced the lacunary [MS4Cu3.75Cl1.75bipy2]. The different species were characterized by X-ray diffraction studies.

Reaction of [MS4]2–(M = Mo or W) with CuCl in dichloromethane or acetonitrile gives a new set of bimetallic compounds isolated with various geometries for the same 1:4:4 M:S:Cu composition. Crystals of [NBu4]2[MoS4Cu4Cl4]1a are tetragonal, space group I/m, a= 13.343(5), c= 14.113(2)A, Z= 2, R= 0.058. The crystal structure reveals discrete [MoS4Cu4Cl4]2– anions separated in the lattice by [NBu4]+ cations. The isostructural tungsten homologue 1b was isolated and characterized: space group I/m, tetragonal, a= 13.342(4), c= 14.106(5)A. The structure of [PPh4][NPr4][MoS4Cu4Cl4]2 consists of a dimeric aggregate: monoclinic, space group P21/n, a= 9.962(8), b= 36.951(5), c= 13.114(3)A, β= 105.71(6)°, R= 0.056. The salt [NPr4]2[WS4Cu4Cl4]3b is polymerized through linear chains. Crystals are triclinic, space group P, a= 10.283(1), b= 13.925(1), c= 15.245(1)A, α= 110.32(1), β= 90.64(1), γ= 102.49(1)°, Z= 2, R= 0.031. The isostructural molybdenum compound 3a was also characterized: triclinic, a= 10.275, b= 13.961, c= 15.270 A, α= 110.57, β= 90.70, γ= 102.30°. The arrangements of the mono-, di- and poly-meric aggregates in the lattice are discussed in terms of the size of the counter anion. For compounds 1b and 3a only the cell dimensions were determined.

The compounds [Rh2(μ-OAc)4(terpy)2] (1) and [Rh2Cl2(μ-OAc)(terpy)2](H3O)Cl2·9H2O (2) have been synthesized in reactions of [Rh2(μ-OAc)4(H2O)2] with 2,2‘:6‘,2‘‘-terpyridine (terpy) (compound 1) and with terpy and NaCl (compound 2) in ethanol using stoichiometric quantities of reactants. Both compounds were structurally and spectroscopically characterized. In 1 terpyridine acts as a monodentate ligand. The compound 2 is the first Rh(II) complex containing only one carboxylato bridging ligand to be analyzed crystallographically. The Rh−Rh distance in 1 is considerably shorter than in 2. The complex 2 in basic solutions in alcohols is an efficient catalyst for reduction of ketones.

The mono- and di-cations of decamethylbiferrocene (1) have been obtained as triiodide salts by oxidation of decamethylbiferrocene with I2 in THF. The X-ray crystal structure of [1](I3) at 295 K and the Mossbauer data show a localized mixed-valence system. The salt [1] (I3)2 has a single Mossbauer quadrupole doublet at 4.5 K with FeIII parameters (IS = 0.537 mm s−1 vs. Fe; QS = 0.237 mm s−1) with small antiferromagnetic coupling (θ = −5.58 K).

Translation is regulated predominantly at the initiation phase by several signal transduction pathways that are often usurped in human cancers, including the PI3K/Akt/mTOR axis. mTOR exerts unique administration over translation by regulating assembly of eukaryotic initiation factor (eIF) 4F, a heterotrimeric complex responsible for recruiting 40S ribosomes (and associated factors) to mRNA 5′ cap structures. Hence, there is much interest in targeted therapies that block eIF4F activity to assess the consequences on tumor cell growth and chemotherapy response. We report here that hippuristanol (Hipp), a translation initiation inhibitor that selectively inhibits the eIF4F RNA helicase subunit, eIF4A, resensitizes Eμ-Myc lymphomas to DNA damaging agents, including those that overexpress eIF4E—a modifier of rapamycin responsiveness. As Mcl-1 levels are significantly affected by Hipp, combining its use with the Bcl-2 family inhibitor, ABT-737, leads to a potent synergistic response in triggering cell death in mouse and human lymphoma and leukemia cells. Suppression of eIF4AI using RNA interference also synergized with ABT-737 in murine lymphomas, highlighting eIF4AI as a therapeutic target for modulating tumor cell response to chemotherapy.

Multiple myeloma (MM) is an incurable malignancy of plasma B lymphoid cells that occurs in the bone marrow. Treatment usually involves autologous stem cell transplantation followed by various combinations of chemotherapies all of which include dexamethasone (DEX) in first-line as well as end-stage therapies. DEX is a steroid hormone analog that binds to the glucocorticoid nuclear receptor and acts by differentially regulating the expression of genes involved in inflammation, and cell death. Despite the utility of glucocorticoids, resistance is common and MM remains an incurable disease. Using a pooled shRNA screening approach, MCL1 was identified as a gene whose knock-down confers increased sensitivity to dexamethasone. MCL-1 is an anti-apoptotic Bcl-2 family member often over-expressed in multiple cancers including MM, and has been linked with resistance to chemotherapy. Obatoclax is a pan BCL-2 family inhibitor that potently disrupts MCL-1/BAK interactions and is highly cytotoxic to MCL-1 dependent cell lines. The combination of dexamethasone with obatoclax results in a synergistic inhibition of MM cell line growth. The synergy is most pronounced when cells are pre-treated for 48h with dexamethasone suggesting the involvement of gene regulation in the combination therapy. BIM, a pro-apoptotic MCL-1 binding partner, is induced in multiple myeloma cells in vitro and in vivo in the Vk*myc murine MM model following dexamethasone treatment. BIM induction is important for BAK and BAX oligomerization at the mitochondrial membrane initiating the cell death response and is required for dexamethasone mediated cell killing of MM cells. Obatoclax is effective as a single agent in the Vk*myc model and is currently being evaluated in combination with dexamethasone. In a second genome-wide siRNA screen in MM cells, knockdown of Aurora kinase B (AURKB) was identified as a dexamethasone sensitizer. The AURKB specific inhibitor, AZD1152 synergizes with dexamethasone in several cell lines, when treatment with AZD1152 precedes that of dexamethasone. A KMS-11 cell line overexpressing BCL-2 can inhibit the synergy between AZD1152 and dexamethasone, demonstrating the involvement of the BCL-2 family of apoptotic regulators in cell death mediated by the combination. The synergy may be in part mediated through TP53 as knockdown of TP53 with siRNAs eliminates AZD1152-mediated cell death. SiRNA-mediated knockdown experiments show that two TP53 regulated genes and pro-apoptotic members of the BCL-2 family, NOXA and PUMA, are also involved in the mechanism of cell death. PUMA, like BIM, is an activator of BAK/BAX mediated outer mitochondrial memebrane permeabilization (MOMP) and NOXA is a sensitizer protein that can displace the activator proteins from MCL-1/BCL-2 inhibitors thus sensitizing cells to MOMP. The AZD1152/DEX combination is currently being tested in the Vk*myc murine model of MM. These results propose two potential new combination therapies that operate through a mechanism involving DEX mediated BIM induction and by modulation of BCL-2 family rheostat. Obatoclax inhibits the function of anti-apoptotic MCL-1 activity and AZD1152 leads to induction of NOXA and PUMA protein, sensitizing the cells to DEX mediated cell death. Citation Format: Anne Roulston, Cynthia Bernier, Mai Nguyen, Franziska Ertel, Francis Robert, Maryanne Bellomo, Xian Fang Huang, Alexandre Bramoullé, Michel Gravel, Michael Sebag, Jerry Pelletier, Gordon Shore. Dexamethasone synthetic lethal screens uncover two potential combination therapies for the treatment of multiple myeloma. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Synthetic Lethal Approaches to Cancer Vulnerabilities; May 17-20, 2013; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(5 Suppl):Abstract nr B17.

The non hydrolytic synthesis of several titanium oxo-alkoxo clusters Ti3O(OPri) 8(OR)2, Ti11O13(OPri)18, Ti7O4(OEt)20 and Ti16O16(OEt )32 have been performed via thermolysis of different titanium alkoxides (Ti(OEt)4, Ti(OPri)4). The structures of these clusters were mainly determined by X-ray diffraction, 17O NMR and 13 C NMR.

The reaction of NH4VO3 with S 2 -2 in ammonia in the presence of 2,2′-bipyridine (bipy) and [N(Bu)4]Br gives the mononuclear compound [N(Bu)4][V(O)(S2)2bipy] (1) isolated at room temperature in crystalline form. The X-ray crystal structure determination shows that the vanadium(V) centre is ligated by four sulphur atoms and a nitrogen atom of the bipy ligand forming the equatorial plane of pentagonal bipyramid, an oxygen and the remaining nitrogen atom of the bipy occupying the two apices of the bipyramid.

Summary The reaction of hydrogen peroxide with tungstic acid, “H 2 WO 4 ”, or H 3 [PW 12 O 40 ]aq and orthophosphoric acid has been studied, and the formation of novel oxoperoxotungstophosphate species, [PwxOy] ω- has been demonstrated. Some of them have been isolated and can be grafted onto polymeric supports. They are active oxygen-to-olefin transfer agents, in association with H 2 O 2 ; these novel catalysts are compared with phase transfer systems.