Intracellular level of S. cerevisiae Rad51 is regulated via proteolysis in a SUMO- and Ubiquitin-dependent manner

Abstract

Among various DNA lesions, the DNA double-strand breaks are particularly deleterious; especially, when an error-free repair pathway is unavailable, and the cell takes the risk of using the error-prone recombination pathways to repair the DNA breaks, resume the cell cycle, and continue growth. The latter comes at the expense of decreased well-being of the cells due to genome rearrangements. One of the major players involved in recombinational repair of DNA damage is Rad51 recombinase, a protein responsible for presynaptic complex formation. We previously noticed that the level of this protein is strongly increased when illegitimate recombination is engaged in repair. The regulation of Rad51 protein turnover is not known; therefore, we decided to look closer at this issue because we expect that an excessively high level of Rad51 may lead to genome instability. Here we show that the level of Rad51 is regulated via the ubiquitin-dependent proteolytic pathway. The ubiquitination of Rad51 depends on multiple E3 enzymes, including SUMO-targeted ubiquitin ligases. We also demonstrate that Rad51 can be modified by both ubiquitin and SUMO. Moreover, these modifications may lead to opposite effects. Ubiquitin-dependent degradation depends on Rad6, Rad18, Slx8, Dia2 and the anaphase-promoting complex. Rsp5-dependent ubiquitination leads to Rad51 stabilization.