No abstract

The Swi1 and Swi3 proteins are required for mat1 imprinting and mating-type switching in Schizosaccharomyces pombe, where they mediate a pause of leading-strand replication in response to a lagging-strand signal. In addition, Swi1 has been demonstrated to be involved in the checkpoint response to stalled replication forks, as was described for the Saccharomyces cerevisiae homologue Tof1. This study addresses the roles of Swi1 and Swi3 during a replication process perturbed by the presence of template bases alkylated by methyl methanesulfonate (MMS). Both the swi1 and swi3 mutations have additive effects on MMS sensitivity and on the MMS-induced damage checkpoint response when combined with chk1 and cds1, but they are nonadditive with hsk1. Cells with swi1, swi3, or hsk1 mutations are also defective in slowing progression through S phase in response to MMS damage. Moreover, swi1 and swi3 strains show increased levels of genomic instability even in the absence of exogenously induced DNA damage. Chromosome fragmentation, increased levels of singlestranded DNA, increased recombination, and instability of replication forks stalled in the presence of hydroxyurea are observed, consistent with the possibility that the replication process is affected in these mutants. In conclusion, Swi1, Swi3, and Hsk1 act in a novel S-phase checkpoint pathway that contributes to replication fork maintenance and to survival of alkylation damage.

The nuclear receptor retinoic acid receptor-related orphan receptor gamma (RORγ or RORc) is a key transcription factor for the production of pro-inflammatory cytokines implicated in the pathogenesis of autoimmune diseases. Recently, small molecule inhibitors of RORc drew the enormous attention of the research community worldwide as a possible therapy for autoimmune diseases, mediated by the IL-17 cytokine. With the clinical proof-of-concept inferred from a small molecule inhibitor VTP-43742 for psoriasis and recent inflow of several RORc inhibitors into the clinic for therapeutic interventions in autoimmune diseases, this field continues to evolve. This review briefly summarizes the RORc inhibitors disclosed in the literature and discusses the progress made by these inhibitors in combating autoimmune diseases.

The eukaryotic intra-S-phase checkpoint, which slows DNA synthesis in response to DNA damage, is poorly understood. Is DNA damage recognized directly, or indirectly through its effects on replication forks? Is the slowing of S phase in part because of competition between DNA synthesis and recombination͞repair processes? The results of our genetic analyses of the intra-S-phase checkpoint in the fission yeast, Schizosaccharomyces pombe, suggest that the slowing of S phase depends weakly on the helicases Rqh1 and Srs2 but not on other recombination͞repair pathways. The slowing of S phase depends strongly on the six checkpoint-Rad proteins, on Cds1, and on Rad4͞Cut5 (similar to budding yeast Dpb11, which interacts with DNA polymerase ) but not on Rhp9 (similar to budding yeast Rad9, necessary for direct damage recognition). These results suggest that, in fission yeast, the signal activating the intra-S-phase checkpoint is generated only when replication forks encounter DNA damage.