Search

AbstractThe recent change towards advanced technologies favors skill-intensive labor, motivating workers to upgrade their educational achievements to the tertiary level. However, workers in many developing countries cannot exploit the opportunity for premium wages in skill-intensive sectors owing to insufficient education facilities and resources. In such contexts, aid to education provides a capacity-building tool to eliminate the insufficiency but is often unsuccessful. Using theories of trade and human capital, this study argues that complementarity between education aid and skill-intensive manufactured exports creates a synergistic effect in upgrading educational achievements by rectifying both structural and incentive constraints. Through extensive data analysis, the result demonstrates that skill-intensive exports enhance aid's effectiveness in increasing tertiary school enrollment, whereas neither exports nor aid alone significantly affect enrollment. It further shows that the aid–export complementarity is less relevant in low-income countries, whereas skill-intensive exports alone promote education upgrading in developed countries via the Stolper–Samuelson effect.

Non-coding RNAs have an integral regulatory role in numerous functions related to lung cancer development. Here, we report identification of a novel lncRNA, termed TP53-inhibitinglncRNA(TILR), which was found to function as a constitutive negative regulator of p53 expression, including activation of downstream genes such as p21and MDM2, and induction of apoptosis. A proteomic search for TILR-associated proteins revealed an association with PCBP2, while the mid-portion of TILRwas found to be required for both PCBP2 and p53mRNA binding. In addition, depletion of PCBP2 resulted in phenocopied effects of TILRsilencing. TILRwas also shown to suppress p53 expression in a post-transcriptional manner, as well as via a positive feedback loop involving p53 and Fanconi anemia pathway genes. Taken together, the present findings clearly demonstrate that TILRconstitutively inhibits p53 expression in cooperation with PCBP2, thus maintaining p53 transcriptional activity at a level sufficiently low for avoidance of spurious apoptosis induction.

Breast cancer, the most common malignancy among women, is closely associated with mutations in the tumor suppressor gene BRCA. DSS1, a component of the TRanscription–EXport-2 (TREX-2) complex involved in transcription and mRNA nuclear export, stabilizes BRCA2 expression. DSS1 is also related to poor prognosis in patients with breast cancer owing to the induction of chemoresistance. Recently, BRCA2 was shown to be associated with the TREX-2 component PCID2, which prevents DNA:RNA hybrid R-loop formation and transcription-coupled DNA damage. This study aimed to elucidate the involvement of these TREX-2 components and BRCA2 in the chemosensitivity of breast carcinomas. Our results showed that compared with that in normal breast tissues, DSS1 expression was upregulated in human breast carcinoma, whereas PCID2 expression was comparable between normal and malignant tissues. We then compared patient survival time among groups divided by high or low expressions of DSS1, BRCA2, and PCID2. Increased DSS1expression was significantly correlated with poor prognosis in recurrence-free survival time, whereas no differences were detected in the high and low BRCA2and PCID2expression groups. We performed in vitro analyses, including propidium iodide nuclear staining, single-cell gel electrophoresis, and clonogenic survival assays, using breast carcinoma cell lines. The results confirmed that DSS1depletion significantly increased chemosensitivity, whereas overexpression conferred chemoresistance to breast cancer cell lines; however, BRCA2expression did not affect chemosensitivity. Similar to DSS1, PCID2expression was also inversely correlated with chemosensitivity. These results strongly suggest that DSS1 and PCID2 depletion is closely associated with increased chemosensitivity via BRCA2-independent DNA damage. Together with the finding that DSS1 is not highly expressed in normal breast tissues, these results demonstrate that DSS1 depletion confers a druggable trait and may contribute to the development of novel chemotherapeutic strategies to treat DSS1-depleted breast carcinomas independent of BRCA2mutations.

Breast cancer, the most common malignancy among women, is closely associated with mutations in the tumor suppressor gene BRCA. DSS1, a component of the TRanscription–EXport-2 (TREX-2) complex involved in transcription and mRNA nuclear export, stabilizes BRCA2 expression. DSS1 is also related to poor prognosis in patients with breast cancer owing to the induction of chemoresistance. Recently, BRCA2 was shown to be associated with the TREX-2 component PCID2, which prevents DNA:RNA hybrid R-loop formation and transcription-coupled DNA damage. This study aimed to elucidate the involvement of these TREX-2 components and BRCA2 in the chemosensitivity of breast carcinomas. Our results showed that compared with that in normal breast tissues, DSS1 expression was upregulated in human breast carcinoma, whereas PCID2 expression was comparable between normal and malignant tissues. We then compared patient survival time among groups divided by high or low expressions of DSS1, BRCA2, and PCID2. Increased DSS1expression was significantly correlated with poor prognosis in recurrence-free survival time, whereas no differences were detected in the high and low BRCA2and PCID2expression groups. We performed in vitro analyses, including propidium iodide nuclear staining, single-cell gel electrophoresis, and clonogenic survival assays, using breast carcinoma cell lines. The results confirmed that DSS1depletion significantly increased chemosensitivity, whereas overexpression conferred chemoresistance to breast cancer cell lines; however, BRCA2expression did not affect chemosensitivity. Similar to DSS1, PCID2expression was also inversely correlated with chemosensitivity. These results strongly suggest that DSS1 and PCID2 depletion is closely associated with increased chemosensitivity via BRCA2-independent DNA damage. Together with the finding that DSS1 is not highly expressed in normal breast tissues, these results demonstrate that DSS1 depletion confers a druggable trait and may contribute to the development of novel chemotherapeutic strategies to treat DSS1-depleted breast carcinomas independent of BRCA2mutations.

Disease progression in castrate-resistant prostate cancer (PCa) is most commonly driven by the reactivation of androgen receptor (AR) signaling and involves AR splice variants including ARV7.

In arthropods, hemolymph carries immune cells and solubilizes and transports nutrients, hormones, and other molecules that are involved in diverse physiological processes including immunity, metabolism, and reproduction. However, despite such physiological importance, little is known about its composition. We applied mass spectrometry-based label-free quantification approaches to study the proteome of hemolymph perfused from sugar-fed female and male Aedes aegyptimosquitoes. A total of 1403 proteins were identified, out of which 447 of them were predicted to be extracellular. In both sexes, almost half of these extracellular proteins were predicted to be involved in defense/immune response, and their relative abundances (based on their intensity-based absolute quantification, iBAQ) were 37.9 and 33.2%, respectively. Interestingly, among them, 102 serine proteases/serine protease-homologues were identified, with almost half of them containing CLIP regulatory domains. Moreover, proteins belonging to families classically described as chemoreceptors, such as odorant-binding proteins (OBPs) and chemosensory proteins (CSPs), were also highly abundant in the hemolymph of both sexes. Our data provide a comprehensive catalogue of A. aegyptihemolymph basal protein content, revealing numerous unexplored targets for future research on mosquito physiology and disease transmission. It also provides a reference for future studies on the effect of blood meal and infection on hemolymph composition.

The receptor tyrosine kinase-like orphan receptor 1 (ROR1) is a transcriptional target of the lineage-survival oncogene NKX2–1/TTF-1 in lung adenocarcinomas. In addition to its kinase-dependent role, ROR1 functions as a scaffold protein to facilitate interaction between caveolin-1 (CAV1) and CAVIN1, and consequently maintains caveolae formation, which in turn sustains pro-survival signaling toward AKT from multiple receptor tyrosine kinases (RTKs), including epidermal growth factor receptor (EGFR), MET (proto-oncogene, receptor tyrosine kinase), and IGF-IR (insulin-like growth factor receptor 1). Therefore, ROR1 is an attractive target for overcoming EGFR-TKI resistance due to various mechanisms such as EGFR T790M double mutation and bypass signaling from other RTKs. Here, we report that ROR1 possesses a novel scaffold function indispensable for efficient caveolae-dependent endocytosis. CAVIN3 was found to bind with ROR1 at a site distinct from sites for CAV1 and CAVIN1, a novel function required for proper CAVIN3 subcellular localization and caveolae-dependent endocytosis, but not caveolae formation itself. Furthermore, evidence of a mechanistic link between ROR1-CAVIN3 interaction and consequential caveolae trafficking, which was found to utilize a binding site distinct from those for ROR1 interactions with CAV1 and CAVIN1, with RTK-mediated pro-survival signaling towards AKT in early endosomes in lung adenocarcinoma cells was also obtained. The present findings warrant future study to enable development of novel therapeutic strategies for inhibiting the multifaceted scaffold functions of ROR1 in order to reduce the intolerable death toll from this devastating cancer.

Imatinib (IMT), a specific tyrosine kinase inhibitor (TKI), has drastically changed the treatment strategy for Ph+ ALL (Philadelphia chromosome-positive acute lymphoblastic leukemia). However, TKI resistance remains a serious problem for patient prognosis. Here, a Ph+ ALL cell line NphA2 and the IMT-resistant subline NphA2/STIR were analyzed to identify a potential novel treatment strategy. We also examined other Ph+ ALL cells, MR87 and its IMT-resistant subline, MR87/STIR. IMT induced apoptosis of NphA2 and MR87 but had no effect on resistant sublines. Increased phosphorylated ERK and BCL2, but not BCL-XL, were observed in NphA2/STIR compared with NphA2. NphA2/STIR but not NphA2 was moderately sensitive to U0126, an ERK inhibitor. Interestingly, SP600125, a JNK inhibitor, was potent in cell growth inhibition and apoptosis induction of both parental and IMT-resistant NphA2 and MR87 cells. Moreover, NphA2 and MR87 and their IMT-resistant sublines were sensitive to ABT-199, a specific BCL2 inhibitor. The combination of SP600125 and ABT-199 synergistically suppressed both parental and IMT-resistant cells, including one with T315I mutation, suggesting that Ph+ ALL exhibits high sensitivity to ABT-199 and SP600125 regardless of TKI resistance. This combination might be a possible therapeutic strategy for Ph+ ALL in the future.

Genomic instability plays an important role in cancer susceptibility, though the mechanics of its development remain unclear. An often-stated hypothesis is that error-prone phenotypes in DNA replication or aberrations in translesion DNA synthesis lead to genomic instability and cancer. Mutations in core DNA replication proteins have been identified in human cancer, although DNA replication is essential for cell proliferation and most mutations eliminating this function are deleterious. With recent developments in this field we review and discuss the possible involvement of DNA replication proteins in carcinogenesis.

Immortalized cell lines maintain telomeres by the expression of telomerase or by a mechanism designated alternative lengthening of telomeres (ALT). Although DNA polymerase α (pol-α) is reported to be required for telomere maintenance, the critical role of pol-α in telomere maintenance has not been firmly determined. We examined the role of retinoblastoma protein (pRb) and pol-α in the regulation of telomere length, using telomere-fiber FISH. Telomere length varied dependent on the intracellular abundance of pol-α or pRb in HeLa cells. A proportion of hyper-phosphorylated pRb (ppRb) molecules localized to sites of telomeric DNA replication in HeLa cells. Pol-α might thus contribute to telomere maintenance, and might be regulated by ppRb.

All-trans-retinoic acid (ATRA) induces myeloid differentiation of a human promyelocytic leukemia cell line, NB4, but does not affect its subclone NB4/RA harboring a point-mutated ligand-binding domain (AF2) in retinoic acid receptorα (RARα) gene. We found that ATRA induced the 4-fold elevation of acid sphingomyelinase (ASMase) activity 24 h after treatment in NB4 cells, but not in NB4/RA cells. ATRA did not affect neutral sphingomyelinase activity in either NB4 or NB4/RA. Upon treatment with ATRA, ceramide, the product of an ASMase reaction, accumulated in NB4 cells. Northern blot analysis showed a marked elevation of the ASMasemRNA 8 h after ATRA treatment, reaching a plateau at 24 h. Regulation ofASMasegene expression was studied by a promoter analysis using luciferase reporter assay. The 5′-upstream flanking region of human ASMasegene (−519/+300) conjugated with theluciferasegene was introduced into COS-7 cells. Luciferase activity in transformed cells markedly increased in response to ATRA stimulation when the wild type RARα or the PML/RARα hybrid protein was co-expressed. Deletion experiments revealed that a short sequence at the 5′-end (−519/−485) was indispensable for the ATRA response. Within this short region, two retinoic acid-responsive element-like motifs (TGCCCG and TCTCCT) and one AP2-like motif (CCCTTCCC) were identified. Deletion and base-substitution experiments showed that all three motifs are required for the full expression induced by ATRA. Electrophoresis mobility shift assays with the nuclear extract of ATRA-treated NB4 cells showed that proteins were bound specifically to the probe being mediated by all three motifs in the promoter sequence.

The metabolism of bisphenol A (BPA), an endocrine-disrupting chemical, was studied with a highly purified laccase from the basidiomycete Trametes villosa. The enzyme reaction products ranged widely from water-insoluble to -soluble compounds, one of which was previously identified as 4-isopropenylphenol. 1H NMR and electron-impact mass spectrum analyses showed that one of the insoluble products was a BPA dimer, 5,5′-bis-[1-(4-hydroxy-phenyl)-1-methyl-ethyl]-biphenyl-2,2′-diol. Field-desorption mass spectrum analysis revealed BPA oligomers, some of which contained phenol, within the insoluble fraction. These results indicate that the laccase reaction may contain successive BPA polymerization, followed by either the addition of phenol to the formed oligomers or their decomposition to release 4-isopropenylphenol.

Previous studies indicate that the O-helix ofThermus aquaticus(Taq) DNA polymerase I (pol I) plays an important role in the replication fidelity of the enzyme. This study examines the role of Thr-664, which lies in the middle of the O-helix of Taqpol I. A mutant ofTaqPol I with a proline substitution of Thr-664 (T664P) exhibits much lower replication fidelity than the wild type enzyme in a forward mutation assay. T664P produces base substitution, single-base deletion, and single-base insertion errors at 20-, 5, and 50-fold higher rates than wild type, respectively. In specific activity and steady-state kinetic experiments, T664P was catalytically robust for insertion of correct nucleotides. In contrast, it incorporated incorrect nucleotides 6.1- to 10-fold more efficiently than wild type at a template dC. Mismatched primer termini were extended by T664P 4.2- to 9.5-fold more efficiently than wild type. These data imply that the O-helix with a proline at position 664 functions like wild type Taqpol I for correct nucleotide incorporations, but bends and enlarges the catalytic pocket of the enzyme and increases the rate of nucleotide misincorporation.

In human cells, atypical drug resistance was previously identified with reduced catalytic activity or nuclear localization efficiency of DNA topoisomerase IIα (TOP2α). We have shown two etoposide resistant hTOP2α mutants, K798L and K798P confer resistance to etoposide. In this work, we showed these mutants are also resistant against doxorubicin and mAMSA invivoin the yeast strain ISE2,rad52,top2-4at the non-permissive temperature. We purified these mutants to characterize the drug resistant mechanism. Purified recombinant proteins were 8- to 12-fold more resistant to etoposide and doxorubicin than wild type TOP2α, and 2-fold more resistant to amsacrine, as measured by accumulation of cleavable DNA. These data show that K798L and K798P may be intrinsically resistant against these drugs invitroand that this character may confer atypical multidrug resistant phenotype invivoin yeast.

Accurate transmission of DNA material from one generation to the next is crucial for prolonged cell survival. Following the discovery of DNA polymerse I in Escherichia coli, the DNA polymerase I class of enzymes has served as the prototype for studies on structural and biochemical mechanisms of DNA replication. Recently, a series of genomic, mutagenesis and structural investigations have provided key insights into how Pol I class of enzymes function and evolve. X-ray crystal structures of at least three Pol I class of enzymes have been solved in the presence of DNA and dNTP, thus allowing a detailed description of a productive replication complex. Rapid-quench stop-flow studies have helped define individual steps during nucleotide incorporation and conformational changes that are rate limiting during catalysis. Studies in our laboratory have generated large libraries of active mutant enzymes (8000) containing a variety of substitutions within the active site, some of which exhibit altered biochemical properties. Extensive genomic information of Pol I has recently become available, as over 50 polA genes from different prokaryotic species have been sequenced. In light of these advancements, we review here the structure-function relationships of Pol I, and we highlight those interactions that are responsible for the high fidelity of DNA synthesis. We present a mechanism for “flipping” of the complementary template base to enhance interactions with the incoming nucleotide substrate during DNA synthesis.

The O-helix of DNA polymerases has been implicated in substrate discrimination and replication fidelity. In this study, wild-type Thermus aquaticusDNA polymerase I (Taqpol I) and an O-helix mutant A661E was examined for their ability to discriminate between ribonucleotides and deoxyribonucleotides. Steady-state nucleotide extension kinetics were carried out using a template cytidine and each nucleotide dNTP and rGTP. Wild-type Taqpol I and A661E demonstrated similar Vmaxand Kmvalues for the correct nucleotide dGTP. However, A661E discriminated between incorrect and correct nucleotide less well than wild-type; discrimination was reduced by factors of 9.5-, 5.6- and 15-fold for dATP, dTTP and rGTP, respectively. These data suggest that A661E is efficient polymerases in the presence of the correct deoxynucleotide, dGTP, but it is impaired in ability to discriminate between correct and incorrect deoxyribonucleotides or between ribo- and deoxyribonucleotides. A structural model of Taqpol I is described in which the mutation A661E alters the interactions between the O-helix and the terminal two phosphate groups in the primer strand.

Eosinophil-derived neurotoxin (EDN), a basic ribonuclease found in the large specific granules of eosinophils, belongs to the pancreatic RNase A family. Although its physiological function is still unclear, it has been shown that EDN is a neurotoxin capable of inducing the Gordon phenomenon in rabbits. EDN is also a potent helminthotoxin and can mediate antiviral activity of eosinophils against isolated virions of the respiratory syncytial virus. EDN is a catalytically efficient RNase sharing similar substrate specificity with pancreatic RNase A with its ribonucleolytic activity being absolutely essential for its neurotoxic, helminthotoxic, and antiviral activities. The crystal structure of recombinant human EDN in the unliganded form has been determined previously (Mosimann, S. C., Newton, D. L., Youle, R. J., and James, M. N. G. (1996) J. Mol. Biol.260, 540–552). We have now determined high resolution (1.8 Å) crystal structures for EDN in complex with adenosine-3′,5′-diphosphate (3′,5′-ADP), adenosine-2′,5′-di-phosphate (2′,5′-ADP), adenosine-5′-diphosphate (5′-ADP) as well as for a native structure in the presence of sulfate refined at 1.6 Å. The inhibition constant of these mononucleotides for EDN has been determined. The structures present the first detailed picture of differences between EDN and RNase A in substrate recognition at the ribonucleolytic active site. They also provide a starting point for the design of tight-binding inhibitors, which may be used to restrain the RNase activity of EDN.1HI21HI31HI41HI5

Phe667in the conserved O-helix of Thermus aquaticus(Taq) DNA polymerase I (pol I) is known to be important for discrimination against dideoxy-NTPs. We show here that Phe667is also important for base selection fidelity. In a forward mutation assay at high polymerase concentration, wild type pol I catalyzed frequent A → T and G → T transversions and −1 frameshifts at nonreiterated sites involving loss of a purine immediately downstream of a pyrimidine. The mutants F667L and A661E,I665T,F667L exhibited large decreases in A → T and G → T transversions, and the triple mutant displayed reduction in the aforementioned −1 frameshifts as well. Kinetic analysis showed that the F667L and A661E,I665T,F667L polymerases discriminated against synthesis of A:A mispairs more effectively and catalyzed less extension of A:A mispairs than the wild type enzyme. These data indicate that Phe667functions in maintaining the error frequency and spectrum, and the catalytic efficiency, of wild type pol I. We also found that the strong general mutator activity conferred by the single A661E substitution was entirely suppressed in the A661E, I665T,F667L polymerase, exemplifying how interactions among O-helix residues can contribute to fidelity. We discuss the mutator and anti-mutator mutations in light of recently obtained three-dimensional structures of T. aquaticuspol I.

An expression library for active site mutants of human topoisomerase IIα (TOP2α) was constructed by replacing the sequence encoding residues 793–808 with a randomized oligonucleotide cassette. This plasmid library was transformed into a temperature-sensitive yeast strain (top2-1), and viable transformants were selected at the restrictive temperature. Among the active TOP2α mutants, no substitution was allowed at Tyr805, the 5′ anchor of the cleaved DNA, and only conservative substitutions were allowed at Leu794, Asp797, Ala801, and Arg804. Thus, these 5 residues are critical for human TOP2α activity, and the remaining mutagenized residues are less critical for function. Using the x-ray crystal structure of yeast TOP2 as a structural model, it can be deduced that these 5 functionally important residues lie in a plane. One of the possible functions of this plane may be that it interacts with the DNA substrate upon catalysis. The side chains of Ser803and Lys798, which confer drug resistance, lie adjacent to this plane.

Description

Lithocholic acid (LCA), one of the major components in secondary bile acids, promotes carcinogenesis in rat colon epithelial cells induced by N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG), which methylates DNA. Base‐excision repair of DNA lesions caused by the DNA methylating agents requires DNA polymerase β (pol β). In the present study, we examined 17 kinds of bile acids with respect to inhibition of mammalian DNA polymerases in vitro. Among them, only LCA and its derivatives inhibited DNA polymerases, while other bile acids were not inhibitory. Among eukaryotic DNA polymerases α, β, δ, η, and γ, pol β was the most sensitive to inhibition by LCA. The inhibition mode of pol β was non‐competitive with respect to the DNA template‐primer and was competitive with the substrate, dTTP, with the Kivalue of 10 μM. Chemical structures at the C‐7 and C‐12 positions in the sterol skeleton are important for the inhibitory activity of LCA. This inhibition could contribute to the tumor‐promoting activity of LCA.

Methylococcus capsulatus (Bath) possesses methane monooxygenases (soluble - (sMMO) and particulate - (pMMO)) which are able to catalyse the epoxidation of propylene to propylene oxide. In a previous paper we have shown that the production of the epoxide caused a rapid inactivation of the bioconversion process (Stanley et al, 1992). This paper shows that cultures containing pMMO, inactivated by propylene oxide production, could be completely reactivated in the presence of growth substrates within 5 h after the removal of propylene oxide so long as the propylene oxide production rate was below 150 nmol min-1 [mg dry weight cells]-1. Reactivation under these conditions was detectable within 30 min of propylene oxide removal. On the other hand, cells inactivated by propylene oxide production rates in excess of 150 nmol min-1 [mg dry weight]-1 did not begin to recover activity within the 30 min period. Furthermore a lag period was observed before reactivation began which was dependent upon the initial production rate. Cultures possessing sMMO took twice as long to recover their activity compared with cells containing pMMO.Reactivation of propylene oxide production could occur without growth, but the process required the presence of a carbon and energy source (methane or methanol), sulphur, nitrogen and oxygen, although copper (which is normally involved in pMMO activity) was not required. It was shown that de novo protein synthesis was required for reactivation of activity.Production rates of 12 g 1-1 d-1 could be maintained for longer than three weeks in a single phase production process and rates up to 30 g 1-1 d-1 were achieved in a two stage process. Using Methylocystis parvus (OBBP) rates of up to 90 g 1-1 d-1 were attained over a one week period.

Methylococcus capsulatus (Bath) possesses methane monooxygenase (MMO) which catalyses the epoxidation of propylene to propylene oxide. MMO activity could be maintained in whole cells by storage in unagitated vessels for several days. However if these cells were agitated and aerated in the absence of a carbon and energy source then 80% of the propylene-oxidizing activity Was lost within 24 h. It was shown that this loss of activity was due to the inability of the cells to provide energy to drive the oxidation process rather than the loss of MMO activity per se. If propylene oxide was added to these aerated cells then the rate of inactivation was increased and 50% of the activity was lost over a 10 min period. The addition of an exogenous energy source caused a doubling in the rate of inactivation. These marked increases in the rates of inactivation in the presence of propylene oxide were found to be caused by the loss of the methane monooxygenase activity per se rather than a further loss of the energy-producing systems. Cells actively producing propylene oxide from propylene, using methanol as an energy source, also lost their propylene oxide-producing capacity rapidly due to loss of the methane monooxygenase activity. The rate of inactivation under these circumstances was related to the rate of propylene oxide production from propylene rather than the level of this product in the culture supernatant.

Sphingosine is a potent inhibitor of a mammalian DNA primase in vitro (Simbulan et al., Biochemistry 33, 9007‐9012, 1994). Here we measured the inhibition of DNA primase in vitro by 9 sphingosine‐analogues with respect to RNA primer synthesis and DNA primase‐dependent DNA synthesis, and their potencies of inhibition in vitro were compared with their in vivo effects on human leukemic cells. Sphingosine, phytosphingosine and N, N‐dimethylsphingosine strongly inhibited the activity of purified calf thymus DNA primase, and also inhibited the growth of human leukemic cell line HL‐60, exerting strong cytotoxicity. Dihydrosphingosine and cis‐sphingosine, which showed more subtle inhibition of DNA primase in vitro, moderately inhibited the cell growth in vivo and caused cell death. In contrast, N‐acyl‐, N‐octyl‐, and N‐acetylsphingosine (ceramides) showing little inhibition of DNA primase suppressed cell growth only slightly. HL 60 cell was arrested at Go/G1 phase by exogenously added sphingosine. From these results, it is suggested that DNA primase is one of targets of sphingosine, an effector molecule in apoptosis.

An oncogene product, p53, interacts with a simian virus 40-encoded T-antigen, which is an initiation protein for the viral DNA replication and also works as DNA helicase during elongation. Here we examine the interaction of p53 with cellular DNA helicase. A recombinant human wild type p53 fused with glutathione S-transferase was immobilized on glutathione-agarose as a ligand for affinity column. Hela cell extract was applied to the p53 column and the adsorbed proteins were eluted with buffers containing salt, 50% ethylene glycol, and glutathione. The ethylene glycol fraction contained a number of p53 binding proteins, and this fraction showed a DNA helicase activity measured by the displacement of DNA fragment from partially duplexed M13 DNA. The DNA helicase translocated in a 5′-to-3′ direction on the single-stranded DNA using ATP as an energy source. The glutathione fraction that contained the p53 glutathione S-transferase fused protein also showed the same activity. The corresponding fractions from a control column carrying glutathione S-transferase showed only a trace amount of activity of DNA helicase. Therefore, the binding may be specific. Furthermore, an anti-p53 antibody column retained a p53-DNA helicase complex when the crude extracts of human placenta and of osteosarcoma cells were applied. These results indicate that p53 physically interacts with DNA helicase in vitroas well as in vivo.

Some new 5'-triphosphate derivatives of 2',3'-dideoxy-5-styryluridine analogues have been synthesized and examined for their inhibitory effects on retroviral reverse transcriptases and eukaryotic DNA polymerases. We describe here the mode of inhibition and the influence of the substituent at the 5-position of uracil ring of 2',3'-dideoxyUTP analogues.

The proton spin relaxivities (R1, R2) of agarose phantom with magnetite particles were measured using an NMR spectrometer at 5.875 T, and compared with other magnetic substances. R2for the polyethylene glycol-coated magnetite particle (PEG-magnetite) was 455 s−1mM−1(M = mol dm−3), 50- and 95-times larger than that for FeCl3and Gd(H2dtpa), respectively. PEG-magnetite also showed a high R2/R1ratio of 172, while the latter two substances had low R2/R1ratios below 10. The core size greatly affected R2, the maximum R2value being observed in the case of the intermediate size (10 nm) among three different core sizes of magnetite. The basic characteristics of magnetite were found to be derived from its magnetism. The optimization of such acquisition parameters as TRand TEfor spin-echo pulse sequences was also examined. The differences in the calculated signal intensity obtained from a tumor with PEG-magnetite and from normal tissue without PEG-magnetite were compared. The image with the highest contrast was found to be obtained at TE= 40 ms and an appropriately long TR. PEG-magnetite is expected to work well as a negative-contrast agent under suitable acquisition conditions.

Degradation of bisphenol A (BPA), an endocrine-disrupting chemical, was studied with a purified laccase from the basidiomycete Trametes villosa. SDS–polyacrylamide gel electrophoresis of the purified laccase gave one single band with a mobility corresponding to MW 65 kDa. The absorption spectrum showed the characteristics of a blue copper protein with a maximum peak at 600 nm. HPLC analysis revealed that 2.2 μmol BPA were degraded by incubation with 1.5 units of the purified laccase in a total volume of 1.0 ml at pH 6.0 and 60°C for 3 h. The enzyme reaction proceeded rapidly without requirement of mediators for the electron transfer. Isolation and identification of several reaction products are in progress, in which one product was identified as 4-isopropenylphenol by a gas chromatography–mass spectrophotometer.

BAX is a pro-apoptotic protein of the BCL-2 family stationed in the cytosol until activated by a diversity of stress stimuli to induce cell death. Because of its role as a critical gatekeeper of cell death, pharmacologic modulation of BAX has the potential to respectively activate or inhibit apoptosis in hematologic diseases characterized by unrestrained cell survival or pathologic cell death. BAX activation is believed to be a highly regulated, multi-step process involving an interaction-triggered conformational change, mitochondrial translocation, and oligomerization that ultimately leads to mitochondrial dysfunction and apoptosis. Anti-apoptotic proteins, such as BCL-2 and BCL-XL, counteract BAX-mediated apoptosis. Although an interaction site that endows anti-apoptotic proteins with survival functionality has been defined and drugged, an activation site has not been identified for BAX, rendering its explicit trigger mechanism unknown. We previously developed Stabilized Alpha-Helix of BCL-2 domains (SAHBs) that target BCL-2 family proteins in situ, directly initiate BAX-mediated mitochondrial apoptosis in vitro, and suppress leukemia in vivo. Here we demonstrate by NMR analysis that a BIM SAHB peptide binds BAX at an interaction site that is distinct from the canonical binding groove characterized for anti-apoptotic proteins. In five distinct assays that measure ligand-induced BAX activation, BIM SAHB directly and dose-responsively triggers BAX. The specificity of the BAX-BIM SAHB interaction is highlighted by point mutagenesis that abrogates functional activity in vitro and in cells, confirming that BAX activation is initiated at this novel structural location. Thus, we report the first structural analysis of a BH3 death domain alpha-helix bound to a full length pro-apoptotic multi- BH domain protein, unveiling a novel site of protein interaction for direct activation of BAX and pharmacologic modulation of apoptosis.

BAX is a pro-apoptotic protein of the BCL-2 family stationed in the cytosol until activated by a diversity of stress stimuli to induce cell death. Because of its role as a critical gatekeeper of cell death, pharmacologic modulation of BAX has the potential to respectively activate or inhibit apoptosis in hematologic diseases characterized by unrestrained cell survival or pathologic cell death. BAX activation is believed to be a highly regulated, multi-step process involving an interaction-triggered conformational change, mitochondrial translocation, and oligomerization that ultimately leads to mitochondrial dysfunction and apoptosis. Anti-apoptotic proteins, such as BCL-2 and BCL-XL, counteract BAX-mediated apoptosis. Although an interaction site that endows anti-apoptotic proteins with survival functionality has been defined and drugged, an activation site has not been identified for BAX, rendering its explicit trigger mechanism unknown. We previously developed Stabilized Alpha-Helix of BCL-2 domains (SAHBs) that target BCL-2 family proteins in situ, directly initiate BAX-mediated mitochondrial apoptosis in vitro, and suppress leukemia in vivo. Here we demonstrate by NMR analysis that a BIM SAHB peptide binds BAX at an interaction site that is distinct from the canonical binding groove characterized for anti-apoptotic proteins. In five distinct assays that measure ligand-induced BAX activation, BIM SAHB directly and dose-responsively triggers BAX. The specificity of the BAX-BIM SAHB interaction is highlighted by point mutagenesis that abrogates functional activity in vitroand in cells, confirming that BAX activation is initiated at this novel structural location. Thus, we report the first structural analysis of a BH3 death domain alpha-helix bound to a full length pro-apoptotic multi- BH domain protein, unveiling a novel site of protein interaction for direct activation of BAX and pharmacologic modulation of apoptosis.

We reported that the RFP gene encodes a protein with putative zinc finger domains and was involved In the activation of the ret proto-oncogene. To further characterize the RFP protein, we developed a polyclonal antibody against the product synthesized from a fragment of the RFP cDNA expressed in Escherichia coll. Western blot analysis showed that RFP was identified as a 58 kDa protein In cell lysates from four human and rodent cell lines and from mouse test is. In addition, a unique 68 kDa protein was detected in the testis. Using AH7974 (rat ascites hepatoma) and Raji (human Burkttt lymphoma) cells, we demonstrated strong association of RFP with the nuclear matrix. Furthermore, RFP solubilized from the nuclear matrix had DNA-bindlng activity although It appears to bind more preferentially to double-stranded DNA than to single-stranded DNA. These results thus suggest that RFP may play a role in molecular processes which occur in the nuclear matrix.