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12 páginas, 6 figuras, The serine/threonine phosphatase PP2A and the cysteine protease Caspase 9 are two proteins involved in physiological and pathological processes, including cancer and apoptosis. We previously demonstrated the interaction between Caspase 9 and PP2A and identified the C9h peptide, corresponding to the binding site of Caspase 9 to PP2A. This interfering peptide can modulate Caspase 9/PP2A interaction leading to a strong therapeutic effect in vitro and in vivo in mouse models of tumor progression. In this manuscript, we investigate (I) the peptide binding to PP2A combining docking with molecular dynamics and (II) the secondary structure of the peptide using CD spectroscopy. Additionally, we compare the binding affinity, using biolayer interferometry, of the wild-type protein PP2A with Caspase 9 and vice versa to that observed between the PP2A protein and the interfering peptide C9h. This result strongly encourages the use of peptides as new therapeutics against cancer, as shown for the C9h peptide already in clinical trial., This work was supported by Inserm. JB work was funded by the Spanish Ministry of Science and Innovation PID 2020-120243RB-100

8 páginas, 2 figuras, 1 tabla., Ribosome biogenesis is an emerging therapeutic target. It has been proposed that cancer cells are addicted to ribosome production which is therefore considered a druggable pathway in cancer therapy. Cancer cells have been shown to be more sensitive to inhibition of the ribosome production than healthy cells. Initial attempts of inhibiting ribosome biogenesis have been focused on the inhibition of transcription by targeting RNA Pol I. Despite being a promising field of research, several limitations have been identified during the development of RNA Pol I inhibitors, like the lack of specificity or acquired resistance. Ribosome biogenesis is a multistep process and additional points of intervention, downstream the very initial stage, could be investigated. Eukaryotic ribosome maturation involves the participation of more than 200 essential assembly factors that will not be part of the final mature ribosome and frequently require protein-protein interactions to exert their biological action. Using mutagenesis, we have previously shown that alteration of the complex interface between assembly factors impairs proper ribosome maturation in yeast. As a first step toward the developing of ribosome biogenesis inhibitory tools, we have used our previously solved crystal structure of the Chaetomium thermophilum complex between the assembly factors Erb1 and Ytm1 to perform a structure-guided selection of interference peptides. The peptides have been assayed in vitro for their ability to bind their cellular partner using biophysical techniques., Funding was obtained from the Spanish Ministry of Economy, Industry and Competitiveness SAF2017-89901-R and Generalitat Valenciana PROMETEO/2018/055. Open access publication fees have been partially funded by URICI from Consejo Superior de Investigaciones Científicas (CSIC). Molecular graphics and analyses were performed with UCSF Chimera, developed by the Resource for Biocomputing, Visualization, and Informatics at the University of California, San Francisco, with support from NIH P41-GM103311

1 página. Abstract del trabajo presentado en 12ª Reunión de la Red Española de Levaduras. El Escorial, Madrid.11-13 de diciembre de 2019, During eukaryotic ribosome biogenesis more than 200 factors remodel the incipient ribonucleoprotein without being part of the mature ribosome. Some of these factors are required for the synthesis of the ribosome like the Nop7 complex, essential for the synthesis of the 60S subunit. Recent structures of pre-ribome particles open some questions concerning the incorporation and release of the Nop7 complex to the preribosome. This heterotrimer is composed of Nop7, Ytm1 and Erb1 and exists as an independent complex before its incorporation to the immature particle. In vitro crosslinking experiments and biophysical evidences suggest that the trimer might have a different conformation as the one observed in the partial structures associated to pre-ribosomes. This possibility opens new questions about the functions exerted by the complex. In order to investigate these aspects we have performed tandem affinity purification coupled to mass spectrometry using Nop7 and Ytm1 tagged ultracentrifuged samples. Preliminary results are presented and an initial analysis of the proteins detected suggests insights into the Nop7 complex mechanism of action in the preribosome and additional functions non directly related with the ribosomal particles.

21 páginas, 11 figuras, 4 tablas. Material suplementario en http://dx.doi.org/10.1016/j.jmb.2018.05.035, The Escherichia coli homodimeric proteins MnmE and MnmG form a functional complex, MnmEG, that modifies tRNAs using GTP, methylene-tetrahydrofolate, FAD, and glycine or ammonium. MnmE is a tetrahydrofolate- and GTP-binding protein, whereas MnmG is a FAD-binding protein with each protomer composed of the FAD-binding domain, two insertion domains, and the helical C-terminal domain. The detailed mechanism of the MnmEG-mediated reaction remains unclear partially due to incomplete structural information on the free- and substrate-bound forms of the complex. In this study, we show that MnmG can adopt in solution a dimer arrangement (form I) different from that currently considered as the only biologically active (form II). Normal mode analysis indicates that form I can oscillate in a range of open and closed conformations. Using isothermal titration calorimetry and native red electrophoresis, we show that a form-I open conformation, which can be stabilized in vitro by the formation of an interprotomer disulfide bond between the catalytic C277 residues, appears to be involved in the assembly of the MnmEG catalytic center. We also show that residues R196, D253, R436, R554 and E585 are important for the stabilization of form I and the tRNA modification function. We propose that the form I dynamics regulates the alternative access of MnmE and tRNA to the MnmG FAD active site. Finally, we show that the C-terminal region of MnmG contains a sterile alpha motif domain responsible for tRNA-protein and protein-protein interactions., This work was supported by the Spanish Ministry of Economy and Competitiveness (BFU2010-19737 and BFU2014-58673-P to M.-E.A.; BFU2016-78232-P to A.V.-C.), and Generalitat Valenciana(ACOMP/2012/065 to M.-E.A; PROMETEO/2012/061to J.B.). Funding for open access charge: [BFU2014-58673-P to M.-E.A.]

11 páginas, 5 figuras, 1 tabla. Contiene 5 figuras en material suplementario, en este fichero., Human Drg1, a guanine nucleotide binding protein conserved in archaea and eukaryotes, is regulated by Lerepo4. Together they form a complex which interacts with translating ribosomes. Here we have purified and characterized the GTPase activity of Drg1 and three variants, a shortened mutant depleted of the TGS domain, a phosphomimicking mutant and a construct with the two combined mutations. Our data reveal that potassium strongly stimulates the GTPase activity, without changing the monomeric status of Drg1 and that this activity is notably reduced in the mutants. The nature of Lerepo4 association has also been investigated. Dissecting the role of the different domains revealed that Dfrp domain is the sole responsible for the Drg1 increase in thermal stability and the four fold stimulation over its catalytic activity. Lerepo4 action leaves Drg1 affinity for nucleotides unaffected, feasibly favoring a switch I reorientation, mainly via the TGS domain. Drg1 displayed a high temperature optimum of activity at 42°C, suggesting the ability of being active under possible heat stress conditions., This work was supported by Ministerio de Ciencia e Innovación (SAF2009-10667, SAF2012-31405) and Generalitat Valenciana (Prometeo/2012/061), Spain.

24 páginas, 3 figuras, 1 tabla., In the era of biomedicines and engineered carrier systems, cell penetrating peptides (CPPs) have been established as a promising tool for therapeutic application. Likewise, other therapeutic peptides, successful in vivo application of CPPs will strongly depend on peptide stability, the bottleneck for this type of biodegradable molecules. In this review, the authors describe the current knowledge of the in vivo degradation for known CPPs and the different strategies available to provide a higher resistance to metabolic degradation while preserving cell penetration efficiency. Peptide stability can be improved by different means, either modifying the structure to make it unrecognizable to proteases, or preventing access of proteolytic enzymes by applying conformation restriction or shielding strategies.

17 páginas, 12 figuras, 3 tablas, TAX1BP1 is a novel ubiquitin-binding adaptor protein involved in the negative regulation of the NF-kappaB transcription factor, which is a key player in inflammatory responses, immunity and tumorigenesis. TAX1BP1 recruits A20 to the ubiquitinated signaling proteins TRAF6 and RIP1, leading to their A20-mediated deubiquitination and the disruption of IL-1-induced and TNF-induced NF-kappaB signaling, respectively. The two zinc fingers localized at its C-terminus function as novel ubiquitin-binding domains (UBZ, ubiquitin-binding zinc finger). Here we present for the first time both the solution and crystal structures of two classical UBZ domains in tandem within the human TAX1BP1. The relative orientation of the two domains is slightly different in the X-ray structure with respect to the NMR structure, indicating some degree of conformational flexibility, which is rationalized by NMR relaxation data. The observed degree of flexibility and stability between the two UBZ domains might have consequences on the recognition mechanism of interacting partners., M.A.C. is supported by an FPU grant from the Ministerio de Educación y Cultura de España. L.B. and A.G.-P. are FWO post-doc fellows. Work in N.v.N. laboratory is supported by the VIB and the Flanders Hercules Foundation. Work in J.B. laboratory was supported by Ministerio de Ciencia e Innovación (SAF2009-10667 and SAF2012-31405) and Generalitat Valenciana ACOMP/2012/024. We thank support for data collection of ID14-1 staff at the European Synchrotron Radiation Facility.

17 páginas, 8 figuras, 1 tabla. Este fichero contiene 5 figuras y 3 tablas de material suplementario, The CD2AP (CD2-associated protein) and CIN85 (Cbl-interacting protein of 85 kDa) adaptor proteins each employ three Src homology 3 (SH3) domains to cluster protein partners and ensure efficient signal transduction and down-regulation of tyrosine kinase receptors. Using NMR, isothermal titration calorimetry and small-angle X-ray scattering methods, we have characterized several binding modes of the N-terminal SH3 domain (SH3A) of CD2AP and CIN85 with two natural atypical proline-rich regions in CD2 (cluster of differentiation 2) and Cbl-b (Casitas B-lineage lymphoma), and compared these data with previous studies and published crystal structures. Our experiments show that the CD2AP-SH3A domain forms a type II dimer with CD2 and both type I and type II dimeric complexes with Cbl-b. Like CD2AP, the CIN85-SH3A domain forms a type II complex with CD2, but a trimeric complex with Cbl-b, whereby the type I and II interactions take place at the same time. Together, these results explain how multiple interactions among similar SH3 domains and ligands produce a high degree of diversity in tyrosine kinase, cell adhesion or T-cell signaling pathways., This research is funded by grant FQM02838 from the Junta de Andalucía. M.A.C. is supported by an FPU grant from the Spanish Ministry of Education (MEC). A.G-P is an FWO post-doc fellow. J.L.OR is a FEBS post-doc fellow. Work in NvN laboratory is supported by the VIB and the Flanders Hercules Foundation. Work in JB laboratory was supported by Ministerio de Ciencia e Innovación (SAF2009-10667, SAF2012-31405) and Generalitat Valenciana ACOMP/2012/024.

9 Pages, 4 Figures, 1 Table and 2 Supplemental Figures, Sorting nexin 6 (SNX6), a predominantly cytoplasmic protein involved in intracellular trafficking of membrane receptors, was identified as a TGF-β family interactor. However, apart from being a component of the Retromer, little is known about SNX6 cellular functions. Pim-1-dependent SNX6 nuclear translocation has been reported suggesting a putative nuclear role for SNX6. Here, we describe a previously non-reported association of SNX6 with breast cancer metastasis suppressor 1 (BRMS1) protein detected by a yeast two-hybrid screening. The interaction can be reconstituted in vitro and further FRET analysis confirmed the novel interaction. Additionally, we identified their coiled-coil domains as the minimal binding motives required for interaction. Since BRMS1 has been shown to repress transcription, we sought the ability of SNX6 to interfere with this nuclear activity. Using a standard gene reporter assay, we observed that SNX6 increases BRMS1-dependent transcriptional repression. Moreover, over-expression of SNX6 was capable of diminishing trans-activation in a dose-dependent manner., Grant sponsor: MCyT; Grant number: SAF2006-10269. Grant sponsor: MICINN; Grant number: SAF2008-04048-E, SAF2009-10667. Grant sponsor: CSIC; Grant number: 200820I020. Grant sponsor: Fundación-Mutua-Madrileña. Grant sponsor: Conselleria de Sanitat, Generalitat valenciana; Grant number: AP001/10.

3 páginas, 2 figuras, 1 tabla., Breast cancer metastasis suppressor 1 (BRMS1) is an inhibitor of metastatic progression and plays a role in several steps of the metastatic cascade. Apart from the ability of BRMS1 to negatively regulate metastasis formation in breast, melanoma and ovarian tumours, very little is known about the molecular aspects of the antimetastatic properties of BRMS1. Here, the expression, purification and crystallization of a functional fragment of human BRMS1 that is predicted to be a coiled-coil region are reported. The purified fragment crystallized in space group C222(1) using the vapour-diffusion method. The unit-cell parameters were a = 42.6, b = 191.3, c = 71.9 A. The crystals diffracted to 2.0 A resolution and a complete data set was collected under cryoconditions. This is the first structural report of BRMS1., This work was supported by Grant SAF2006-10269 of the “Ministerio de Ciencia y Tecnología” and Fundación Mutua Madrileña, Spain.

3 páginas, 2 figuras, 1 tabla, The Gim complex (GimC) from Saccharomyces cerevisiae is a heterohexameric protein complex, also known as prefoldin (PFD), which binds and stabilizes unfolded target polypeptides and subsequently delivers them to chaperonins for completion of folding. In this study, the crystallization and preliminary X-ray analysis of one of the beta subunits of the Gim complex (Yke2) from S. cerevisiae are described. The purified protein was crystallized by the vapour-diffusion method, producing two types of crystals that belonged to the orthorhombic space group C222 or the primitive monoclinic space group P2(1). The unit-cell parameters for the C-centred orthorhombic crystal were a = 48.2, b = 168.86, c = 131.81 A and the unit-cell parameters for the primitive monoclinic crystal were a = 47.83, b = 134.90, c = 81.50 A, beta = 100.71 degrees . The Yke2 crystals diffracted to 4.2 and 3.1 A resolution, respectively, on a rotating-anode generator under cryoconditions. This is the first report concerning the crystallization of a beta subunit of a eukaryotic prefoldin., This work was supported by Spanish National Cancer Research Centre (CNIO) and it was partially supported by the EU-grant 3D-repertoire (contract LSHG-CT-2005- 512028) and by Grant SAF2006-10269 of the “Ministerio de Ciencia y Tecnología”, Spain.

8 páginas, 5 figuras, 2 tablas, The ubiquitin ligases c-Cbl and Cbl-b play a crucial role in receptor downregulation by mediating multiple monoubiquitination of receptors and promoting their sorting for lysosomal degradation. Their function is modulated through interactions with regulatory proteins including CIN85 and PIX, which recognize a proline-arginine motif in Cbl and thus promote or inhibit receptor endocytosis. We report the structures of SH3 domains of CIN85 and beta-PIX in complex with a proline-arginine peptide from Cbl-b. Both structures reveal a heterotrimeric complex containing two SH3 domains held together by a single peptide. Trimerization also occurs in solution and is facilitated by the pseudo-symmetrical peptide sequence. Moreover, ternary complexes of CIN85 and Cbl are formed in vivo and are important for the ability of Cbl to promote epidermal growth factor receptor (EGFR) downregulation. These results provide molecular explanations for a novel mechanism by which Cbl controls receptor downregulation., Research on CIN85 was supported by grant SAF2003-03860 of the Ministerio de Ciencia y Tecnología, Spain and N.C. received a fellowship from the Ramón Areces Foundation. D.J. and K.R. are funded by the Medical Research Council, UK. Work by Y.L.D, D.H. and I.D. are supported by grants from Deutsche Forschungsgemeinschaft, Germany.

The S:A222V point mutation, within the G clade, was characteristic of the 20E (EU1) SARS-CoV-2 variant identified in Spain in early summer 2020. This mutation has now reappeared in the Delta subvariant AY.4.2, raising questions about its specific effect on viral infection. We report combined serological, functional, structural and computational studies characterizing the impact of this mutation. Our results reveal that S:A222V promotes an increased RBD opening and slightly increases ACE2 binding as compared to the parent S:D614G clade. Finally, S:A222V does not reduce sera neutralization capacity, suggesting it does not affect vaccine effectiveness., This research work was supported by the European Commission–NextGenerationEU through the CSIC Global Health Platform. Additionally, authors would like to acknowledge economic support from the Spanish Ministry of Science and Innovation through Grants: PID2019-104757RB-I00 funded by MCIN/AEI/ 10.13039/501100011033, RTI2018-094399-A-I00, and “ERDF A way of making Europe”, by the “European Union”, Grant SEV 2017-0712 funded by MCIN/AEI /10.13039/501100011033, the “Comunidad Autónoma de Madrid" through Grant: S2017/BMD3817, and the European Union (EU) and Horizon 2020 through grants: Marie-Curie Fellowship EnLaCES (MSCA IF 2020, Proposal: 101024130) (to JK), HighResCells (ERC - 2018 - SyG, Proposal: 810057), and iNEXT-Discovery (Proposal: 871037). AM, VR, JB and JLL are funded by CIBERER-ISCIII (proposal: COV20/00437), Fondo Supera COVID-19 (proposal: CSICCOVID19-082), Banco Santander (Proposal: BlockAce), and CSIC PTI Salud Global (Proposal: 202080E110). VR is funded by the Spanish Ministry of Science and Innovation through Grant PID2020-120322RB-C21. IC is funded by project PID2019-104477RB-100, Fondo COVID COV20/00140 and ERC CoG 101001038. MC is funded by the RyC program from the Spanish Ministry of Science and Innovation, the Generalitat Valenciana (SEJI/2019/011).

The S:A222V point mutation, within the G clade, was characteristic of the 20E (EU1) SARS-CoV-2 variant identified in Spain in early summer 2020. This mutation has since reappeared in the Delta subvariant AY.4.2, raising questions about its specific effect on viral infection. We report combined serological, functional, structural and computational studies characterizing the impact of this mutation. Our results reveal that S:A222V promotes an increased RBD opening and slightly increases ACE2 binding as compared to the parent S:D614G clade. Finally, S:A222V does not reduce sera neutralization capacity, suggesting it does not affect vaccine effectiveness., In this research work, PRR and TG were supported by salaries from the European Commission–NextGenerationEU through the CSIC Global Health Platform established by EU Council Regulation 2020/2094. The authors would like to acknowledge economic support from: (a) the Spanish Ministry of Science and Innovation through grants: SEV-2017-0712 funded by MCIN/AEI/10.13039/501100011033 (CPM, JK, RM, COSS, MM, RA, JMC); 116880GB-I00 (JLL) and 120322RB-C21 (VR) funded within PID 2020; PID2019-104757RB-I00 funded by MCIN/AEI/10.13039/501100011033/ and “ERDF A way of making Europe”, by the “European Union” (JMC, COSS, RM, MM, CPM) and 104477RB-100 (IC) funded within PID 2019; RYC-2015-18213 (salary of MC) and RYC-2015-17517 (salary of RG) funded by the Ramon y Cajal fellowship program; RTI2018-094399-A-I00 (JMC, COSS, RM, CPM, MC) funded within the Retos Investigación program; the CRIOMECORR project funded as ESFRI-2019-01-CSIC-16; (b) the Horizon 2020 program through Marie Skłodowska-Curie Individual Fellowships EnLaCES (Proposal 101024130, salary of JK) and EPIDNA (Grant ID: 894498, salary of MW); (c) the European Research Council (ERC) through grants: ERC-2018-SyG-810057 HighResCells funded within the EXCELLENT SCIENCE program (JMC, MM, COSS, salary of RM), Grant 871037 iNEXT DISCOVERY (JMC, MM, COSS) and grant CoG-101001038 funded within the Consolidator Grants program (IC); (d) Generalitat Valenciana through grants: SEJI/2019/011 (MC) and SEJI/2019/030 (JLL); (e) Comunidad de Madrid through grant: S2017/BMD-3817 (JMC); (f) Santander Bank through grant: CSIC-COVID19-082 (AM, VR, JB, JLL, RG) funded through the Fondo Supera Covid-19; (g) Instituto de Salud Carlos III through grants: COV20/00437 (AM, VR, JB, JLL) and COV20/00140 (IC), both funded through the Fondos Covid-19 initiative; (h) Spanish National Research Council through grant: 202080E110 funded within the PTI Salud Global initiative (AM, VR, JB, JLL, RG).