Synthetic viability genomic screening defines Sae2 function in DNA repair.

DNA double-strand break (DSB) repair by homologous recombination (HR) requires 3' single-stranded DNA (ssDNA) generation by 5' DNA-end resection. During meiosis, yeast Sae2 cooperates with the nuclease Mre11 to remove covalently bound Spo11 from DSB termini, allowing resection and HR to ensue. Mitotic roles of Sae2 and Mre11 nuclease have remained enigmatic, however, since cells lacking these display modest resection defects but marked DNA damage hypersensitivities. By combining classic genetic suppressor screening with high-throughput DNA sequencing, we identify Mre11 mutations that strongly suppress DNA damage sensitivities of sae2∆ cells. By assessing the impacts of these mutations at the cellular, biochemical and structural levels, we propose that, in addition to promoting resection, a crucial role for Sae2 and Mre11 nuclease activity in mitotic DSB repair is to facilitate the removal of Mre11 from ssDNA associated with DSB ends. Thus, without Sae2 or Mre11 nuclease activity, Mre11 bound to partly processed DSBs impairs strand invasion and HR.We thank M.P. Longhese, R. Rothstein and J. Haber for providing strains and plasmids; Sir T. Blundell and T. Ochi for advice on structural biology and for providing comments to the manuscript. Research in the Jackson laboratory is funded by Cancer Research UK Programme Grant C6/A11224, the European Research Council and the European Community Seventh Framework Programme Grant Agreement No. HEALTH‐F2‐2010‐259893 (DDResponse). Core funding is provided by CRUK (C6946/A14492) and the Wellcome Trust (WT092096). SPJ receives his salary from the University of Cambridge, UK, supplemented by CRUK. TO, IG and FP were funded by Framework Programme Grant Agreement No. HEALTH‐F2‐2010‐259893 (DDResponse). FP also received funding from EMBO (Fellowship ALTF 1287‐2011); NG and IS are funded by the Wellcome Trust (101126/Z/13/Z). DJA and TMK were supported by Cancer Research UK and the Wellcome Trust (WT098051). PS and HN were supported by NIH grants RO1ES007061 and K99ES021441, respectively.This is the final version. It was first published by EMBO at http://emboj.embopress.org/content/early/2015/04/21/embj.201590973.lon

Efflux in Fungi: La Pièce de Résistance

Pathogens must be able to overcome both host defenses and antimicrobial treatment in order to successfully infect and maintain colonization of the host. One way fungi accomplish this feat and overcome intercellular toxin accumulation is efflux pumps, in particular ATP-binding cassette transporters and transporters of the major facilitator superfamily. Members of these two superfamilies remove many toxic compounds by coupling transport with ATP hydrolysis or a proton gradient, respectively. Fungal genomes encode a plethora of members of these families of transporters compared to other organisms. In this review we discuss the role these two fungal superfamilies of transporters play in virulence and resistance to antifungal agents. These efflux transporters are responsible not only for export of compounds involved in pathogenesis such as secondary metabolites, but also export of host-derived antimicrobial compounds. In addition, we examine the current knowledge of these transporters in resistance of pathogens to clinically relevant antifungal agents

Frequent and Efficient Use of the Sister Chromatid for DNA Double-Strand Break Repair during Budding Yeast Meiosis

Studies of DNA double-strand break repair during meiosis reveal that a substantial fraction of recombination occurs between sister chromatids

DNA motif associated with meiotic double-strand break regions in Saccharomyces cerevisiae

Meiotic recombination in yeast is initiated by DNA double-strand breaks (DSBs) that occur at preferred sites, distributed along the chromosomes. These DSB sites undergo changes in chromatin structure early in meiosis, but their common features at the level of DNA sequence have not been defined until now. Alignment of 1 kb sequences flanking six well-mapped DSBs has allowed us to define a flexible sequence motif, the CoHR profile, which predicts the great majority of meiotic DSB locations. The 50 bp profile contains a poly(A) tract in its centre and may have several gaps of unrelated sequences over a total length of up to 250 bp. The major exceptions to the correlation between CoHRs and preferred DSB sites are at telomeric regions, where DSBs do not occur. The CoHR sequence may provide the basis for understanding meiosis-induced chromatin changes that enable DSBs to occur at defined chromosomal sites