The Anaphase-Promoting Complex/Cyclosome Controls Repair and Recombination by Ubiquitylating Rhp54 in Fission Yeast

Abstract

Homologous recombination (HR) is important for maintaining genome integrity and for the process of meiotic chromosome segregation and the generation of variation. HR is regulated throughout the cell cycle, being prevalent in the S and G2 phases and suppressed in the G1 phase. Here we show that the anaphase-promoting complex/cyclosome (APC/C) regulates homologous recombination in the fission yeast Schizosaccharomyces pombe by ubiquitylating Rhp54 (an ortholog of Rad54). We show that Rhp54 is a novel APC/C substrate that is destroyed in G1 phase in a KEN-box- and Ste9/Fizzy-related manner. The biological consequences of failing to temporally regulate HR via Rhp54 degradation are seen in haploid cells only in the absence of antirecombinase Srs2 function and are more extensive in diploid cells, which become sensitive to a range of DNA-damaging agents, including hydroxyurea, methyl methanesulfonate, bleomycin, and UV. During meiosis, expression of nondegradable Rhp54 inhibits interhomolog recombination and stimulates sister chromatid recombination. We thus propose that it is critical to control levels of Rhp54 in G1 to suppress HR repair of double-strand breaks and during meiosis to coordinate interhomolog recombination.