Mus81-Mms4 endonuclease is an Esc2-STUbL-Cullin8 mitotic substrate impacting on genome integrity

Abstract

The Mus81-Mms4 nuclease is activated in G2/M via Mms4 phosphorylation to allow resolution of persistent recombination structures. However, the fate of the activated phosphorylated Mms4 remains unknown. Here we find that Mms4 is engaged by (poly)SUMOylation and ubiquitylation and targeted for proteasome degradation, a process linked to the previously described Mms4 phosphorylation cycle. Mms4 is a mitotic substrate for the SUMO-Targeted Ubiquitin ligase Slx5/8, the SUMO-like domain-containing protein Esc2, and the Mms1-Cul8 ubiquitin ligase. In the absence of these activities, phosphorylated Mms4 accumulates on chromatin in an active state in the next G1, subsequently causing abnormal processing of replication-associated recombination intermediates and delaying the activation of the DNA damage checkpoint. Mus81-Mms4 mutants that stabilize phosphorylated Mms4 have similar detrimental effects on genome integrity. Overall, our findings highlight a replication protection function for Esc2-STUbL-Cul8 and emphasize the importance for genome stability of resetting phosphorylated Mms4 from one cycle to another.

Regulation of Mus81-Eme1 structure-specific endonuclease by Eme1 SUMO-binding and Rad3ATR kinase is essential in the absence of Rqh1BLM helicase

“…Interestingly, the presumed S. cerevisiae Rad60 ortholog Esc2 has been reported to interact with Mus81 via its SLDs and to stimulate the Mus81-Mms4 complex [26]. In addition, Esc2 was recently found to promote the degradation of phosphorylated Mms4 [11]. We can Overall, our findings show that the poorly structured N-terminal domain of Eme1 harbors essential regulatory functions of Mus81-Eme1, the control of which appears to be remarkably more elaborate than initially described.…”

“…Having confirmed by yeast two hybrid that SIM1 and SIM2 are bone fide SIMs that bind SUMO (Fig 5A), the most straightforward assumption would be that they are involved in the control of Mus81-Eme1 by jointly driving the interaction of Eme1 with one or several SUMOylated proteins. They could also drive transient conformational changes through internal interactions between the SIMs of Eme1 and SUMOylated Eme1 or Mus81, which both have been reported to undergo SUMOylation in S. cerevisiae and human cells [11,22,23]. Remarkably, we find that SIM1 and SIM2 fulfil independent functions.…”

“…The importance of such control mechanisms is underscored by the marked genomic instability that is caused by the premature stimulation of Mus81-Mms4 in budding yeast cells that produce an Mms4 mutant that mimics a constitutively phosphorylated Mms4 protein [2]. Interestingly, SUMOylation and ubiquitination of Mms4 were recently shown to specifically target phosphorylated Mms4 for degradation by the proteasome, further ensuring that hyperactivation of Mus81-Mms4 is restricted to mitosis [11]. In human cells, SLX4-MUS81 complex formation induced by premature activation of CDK1 results in the unscheduled processing of replication intermediates genome wide and chromosome pulverization [9].…”

Crystal structure of the human MUS81-EME2 complex

“…Thus, the isolated MUS81-EME1 and MUS81-EME2 proteins are identical in substrate recognition and endonuclease activities, while their distinct roles in cells could arise See also Figures S4 and S5. ll Article from the cellular temporal controls, such as phosphorylation or association with other regulators (Palma et al, 2018;Princz et al, 2017;Sebesta et al, 2017;Waizenegger et al, 2020).…”

SUMOylation as a Therapeutic Target for Myocardial Infarction

“…Vivek et al showed that SUMOylation mediated WRKY33 phosphorylation while disruption of WRKY33 SUMO sites inactivated WRKY33-mediated defense ( 37 ). Waizenegger et al found that Mms4 was engaged by (poly)SUMOylation and targeted for proteasome degradation ( 38 ). Moreover, SUMOylation preserves substrate stability by competing with ubiquitination for the lysine residue or by recruiting the SUMO-targeted ubiquitin ligase (STUBL) family of proteins to the SUMOylated substrates.…”