Crystal structures of the Gon7/Pcc1 and Bud32/Cgi121 complexes provide a model for the complete yeast KEOPS complex.

International audienceThe yeast KEOPS protein complex comprising Kae1, Bud32, Cgi121, Pcc1 and Gon7 is responsible for the essential tRNA threonylcarbamoyladenosine (t(6)A) modification. Deletion of genes coding for the KEOPS subunits also affects telomere elongation and transcriptional regulation. In the present work, the crystal structure of Bud32/Cgi121 in complex with ADP revealed that ADP is bound in the catalytic site of Bud32 in a canonical manner characteristic of Protein Kinase A (PKA) family proteins. We found that Gon7 forms a stable heterodimer with Pcc1 and report the crystal structure of the Pcc1-Gon7 heterodimer. Gon7 interacts with the same Pcc1 region engaged in the archaeal Pcc1 homodimer. We further show that yeast KEOPS, unlike its archaeal counterpart, exists as a heteropentamer in which Gon7, Pcc1, Kae1, Bud32 and Cgi121 also adopt a linear arrangement. We constructed a model of yeast KEOPS that provides structural insight into the role of Gon7. The model also revealed the presence of a highly positively charged crater surrounding the entrance of Kae1 that likely binds tRNA

Molecular determinants of the DprA−RecA interaction for nucleation on ssDNA

International audienceNatural transformation is a major mechanism of horizontal gene transfer in bacteria that depends on DNA recombination. RecA is central to the homologous recombination pathway, catalyzing DNA strand invasion and homology search. DprA was shown to be a key binding partner of RecA acting as a specific mediator for its loading on the incoming exogenous ssDNA. Although the 3D structures of both RecA and DprA have been solved, the mechanisms underlying their cross-talk remained elusive. By combining molecular docking simulations and experimental validation, we identified a region on RecA, buried at its self-assembly interface and involving three basic residues that contact an acidic triad of DprA previously shown to be crucial for the interaction. At the core of these patches, DprA M238 and RecA F230 are involved in the interaction. The other DprA binding regions of RecA could involve the N-terminal ␣-helix and a DNA-binding region. Our data favor a model of DprA acting as a cap of the RecA filament, involving a DprA−RecA interplay at two levels: their own oligomeric states and their respective interaction with DNA. Our model forms the basis for a mech-anistic explanation of how DprA can act as a mediator for the loading of RecA on ssDNA

Mutations in KEOPS-Complex Genes Cause Nephrotic Syndrome with Primary Microcephaly

Galloway-Mowat syndrome (GAMOS) is an autosomal-recessive disease characterized by the combination of early-onset nephrotic syndrome (SRNS) and microcephaly with brain anomalies. Here we identified recessive mutations in OSGEP, TP53RK, TPRKB, and LAGE3, genes encoding the four subunits of the KEOPS complex, in 37 individuals from 32 families with GAMOS. CRISPR-Cas9 knockout in zebrafish and mice recapitulated the human phenotype of primary microcephaly and resulted in early lethality. Knockdown of OSGEP, TP53RK, or TPRKB inhibited cell proliferation, which human mutations did not rescue. Furthermore, knockdown of these genes impaired protein translation, caused endoplasmic reticulum stress, activated DNA-damage-response signaling, and ultimately induced apoptosis. Knockdown of OSGEP or TP53RK induced defects in the actin cytoskeleton and decreased the migration rate of human podocytes, an established intermediate phenotype of SRNS. We thus identified four new monogenic causes of GAMOS, describe a link between KEOPS function and human disease, and delineate potential pathogenic mechanisms

Desafíos de la caficultura en Centroamérica

Contiene: 1 Trayectoria y viabilidad de las caficulturas centroamericanas (Mario Samper). 2 Aspectos de la sostenibilidad de los sistemas de cultivo de café en América Central (Carlos E. Fernández y Reinhold G. Muschler). 3 Los suelos cafetaleros en América Central y su fertilización (Elemer Bornemisza, Jean Collinet y Alvaro Segura). 4 Hacia un manejo sostenible de la materia orgánica y de la fertilidad biológica de los suelos cafetaleros (Philippe Vaast y Didier Snoeck). 5 El beneficiado ecológico del café (Rolando Vásquez). 6 La roya anaranjada del cafeto: mito y realidad (Jacques Avelino, Raoul Muller, Albertus Eskes, Rodney Santacreo y Francisco Holguín). 7 El ojo de gallo del cafeto (Mycena citricolor) (Amy Wang y Jacques Avelino). 8 La Anthracnosis de los frutos: un grave peligro para la caficultura centroamericana (Raoul A. Müller, Dominique Berry y Daniel Bieysse). 9 La broca de los frutos del cafeto: +la lucha biológica como solución? (Bernard Dufour, Juan Francisco Barrera y Bernard Decazy). 10 Los Nematodos Parásitos del cafeto (Luc Villain, Francisco Anzueto, Adám Hernández y Jean Louis Sarah). 11 Los recursos genéticos: las bases de una solución genética a los problemas de la caficultura latinoamericana (Franéois Anthony, Carlos Astorga y Julien Berthaud). 12 El mejoramiento genético en América Central (Beno¯t Bertrand, Germán Aguilar, Rodney Santacreo y Francisco Anzueto. 13 Aportes de la biotecnología al mejoramiento genético del café: el ejemplo de la multiplicación por embriogénesis somática de híbridos F1 en América Central (Hervé Etienne, Dominique Barry-Etienne, Nelly Vásquez y Marc Berthouly).2 fig. Cuenta con un glosario.Este documento es una recopilación de información realizada por varias autores y autoras. El libro intenta contribuir al debate y desafíos de la investigación cafetalera, presentando los grandes problemas ecológicos, Agronómicos y biológicos que acechan a la caficultura centroamericana, o que la afectarán probablemente en un futuro cercano. El libro comienza por una resena hist6rica que permite tanto entender la diversidad de situaciones de producci6n coma interpretar los debates actuales en un contexto mas amplio de una historia bisecular. Luego, se estudian los principales avances y limitaciones de los sistemas de cultivo con una atención particular del manejo deI suelo con el afán de proponer soluciones, o de identificar campos prioritarios de investigación. También se repasan los grandes desafios deI beneficiado dei café que son principalmente ecológicos. Un gran espacio es dedicado al estudio de las principales enfermedades y plagas deI café, cuyo desarrollo y agravamiento repercute en costos de control muy elevados. La lucha biológica o integrada puede (o podrá) ofrecer soluciones alentadoras. En fin, se presentan las posibilidades de creaci6n de nuevas variedades de café a partir de los recursos genéticos introducidos de Africa, con las esperanzas que despiertan las nuevas biotecnologias

Activation of the LicT transcriptional antiterminator involves a domain swing/lock mechanism provoking massive structural changes.

The transcriptional antiterminator protein LicT regulates the expression of Bacillus subtilis operons involved in β-glucoside metabolism. It consists of an N-terminal RNA-binding domain (co-antiterminator (CAT)) and two phosphorylatable phosphotransferase system regulation domains (PRD1 and PRD2). In the activated state, each PRD forms a dimeric unit with the phosphorylation sites totally buried at the dimer interface. Here we present the 1.95 Å resolution structure of the inactive LicT PRDs as well as the molecular solution structure of the full-length protein deduced from small angle x-ray scattering. Comparison of native (inactive) and mutant (constitutively active) PRD crystal structures shows massive tertiary and quaternary rearrangements of the entire regulatory domain. In the inactive state, a wide swing movement of PRD2 results in dimer opening and brings the phosphorylation sites to the protein surface. This movement is accompanied by additional structural rearrangements of both the PRD1-PRD1 ′ interface and the CAT-PRD1 linker. Small angle x-ray scattering experiments indicate that the amplitude of the PRD2 swing might even be wider in solution than in the crystals. Our results suggest that PRD2 is highly mobile in the native protein, whereas it is locked upon activation by phosphorylation