The SUMO Isopeptidase Ulp2p Is Required to Prevent Recombination-Induced Chromosome Segregation Lethality following DNA Replication Stress

Abstract

SUMO conjugation is a key regulator of the cellular response to DNA replication stress, acting in part to control recombination at stalled DNA replication forks. Here we examine recombination-related phenotypes in yeast mutants defective for the SUMO de-conjugating/chain-editing enzyme Ulp2p. We find that spontaneous recombination is elevated in ulp2 strains and that recombination DNA repair is essential for ulp2 survival. In contrast to other SUMO pathway mutants, however, the frequency of spontaneous chromosome rearrangements is markedly reduced in ulp2 strains, and some types of rearrangements arising through recombination can apparently not be tolerated. In investigating the basis for this, we find DNA repair foci do not disassemble in ulp2 cells during recovery from the replication fork-blocking drug methyl methanesulfonate (MMS), corresponding with an accumulation of X-shaped recombination intermediates. ulp2 cells satisfy the DNA damage checkpoint during MMS recovery and commit to chromosome segregation with similar kinetics to wild-type cells. However, sister chromatids fail to disjoin, resulting in abortive chromosome segregation and cell lethality. This chromosome segregation defect can be rescued by overproducing the anti-recombinase Srs2p, indicating that recombination plays an underlying causal role in blocking chromatid separation. Overall, our results are consistent with a role for Ulp2p in preventing the formation of DNA lesions that must be repaired through recombination. At the same time, Ulp2p is also required to either suppress or resolve recombination-induced attachments between sister chromatids. These opposing defects may synergize to greatly increase the toxicity of DNA replication stress.

Detection of the Wolbachia protein WPIP0282 in mosquito spermathecae: Implications for cytoplasmic incompatibility

“…Ulp1 SUMO proteases were originally described in yeast, where it was shown that alterations in their functionality can lead to G2/M arrest and cell lethality (Li and Hochstrasser, 1999). Interestingly, Ulp1 C48 SUMO protease proteins are also commonly associated with architectural chromatin proteins such as SMC, (Structural Maintenance of Chromosome) proteins and histones which themselves become SUMOylated (Lee et al, 2011; McAleenan et al, 2012; Cubenas-Potts and Matunis, 2013). Alterations in the SUMOylation status of host SMC proteins and/or histones might contribute to induction/rescue of known CI chromatin disruption phenotypes.…”

Function and regulation of SUMO proteases

“…At elevated temperatures and following DNA damage 14 , Ulp2 is essential for cell division, functioning in the resumption of the cell cycle after the checkpoint has been turned off or the DNA damage has been repaired 82, 83 . Under normal conditions, yeast can divide in the absence of Ulp2, but growth is poor, and ulp2 -deficient cells have abnormal cell size and morphology 14 .…”

Ubiquitin family modifications and template switching

“…1). Recently, mutations in the SUMO deconjugating enzyme, Ulp2, were also shown to accumulate SCJ intermediates in response to MMS treatment as well as persistent recombination foci, suggesting that Ulp2 is also required to suppress or facilitate the resolution of the damage‐induced template switch intermediates [120]. The SUMO substrates involved in template switch intermediate resolution are not known, but they may include structural maintenance of chromosomes (SMC), Smc5–6—associated with the Mms21 SUMO ligase, as well as Esc2, an Smc5–6 functionally associated factor with regulatory functions in sumoylation.…”