S. cerevisiaeMre11 recruits conjugated SUMO moieties to facilitate the assembly and function of the Mre11-Rad50-Xrs2 complex

Abstract

Double-strand breaks (DSBs) in chromosomes are the most challenging type of DNA damage. The yeast and mammalian Mre11-Rad50-Xrs2/Nbs1 (MRX/N)-Sae2/Ctp1 complex catalyzes the resection of DSBs induced by secondary structures, chemical adducts or covalently-attached proteins. MRX/N also initiates two parallel DNA damage responses—checkpoint phosphorylation and global SUMOylation—to boost a cell's ability to repair DSBs. However, the molecular mechanism of this SUMO-mediated response is not completely known. In this study, we report that Saccharomyces cerevisiae Mre11 can non-covalently recruit the conjugated SUMO moieties, particularly the poly-SUMO chain. Mre11 has two evolutionarily-conserved SUMO-interacting motifs, Mre11SIM1 and Mre11SIM2, which reside on the outermost surface of Mre11. Mre11SIM1 is indispensable for MRX assembly. Mre11SIM2 non-covalently links MRX with the SUMO enzymes (E2/Ubc9 and E3/Siz2) to promote global SUMOylation of DNA repair proteins. Mre11SIM2 acts independently of checkpoint phosphorylation. During meiosis, the mre11SIM2 mutant, as for mre11S, rad50S and sae2Δ, allows initiation but not processing of Spo11-induced DSBs. Using MRX and DSB repair as a model, our work reveals a general principle in which the conjugated SUMO moieties non-covalently facilitate the assembly and functions of multi-subunit protein complexes.

SUMO-Mediated Regulation of Nuclear Functions and Signaling Processes

“…A well-established example is the upregulation of sumoylation levels of many DNA repair and checkpoint proteins in yeast and human cells after genotoxic stress. This is achieved partly by targeting SUMO E2 and specific SUMO E3s to DNA damage sites (Cremona et al, 2012; Galanty et al, 2009; Morris et al, 2009; Psakhye and Jentsch, 2012) via association between sumoylation enzymes and DNA lesion recognition complexes, including the ssDNA-binding complex RPA and DSB-binding MRX complex (Chen et al, 2016; Chung and Zhao, 2015). The SUMO pathway enzymes also change localization during the cell cycle.…”

Intricate SUMO-based control of the homologous recombination machinery

“…As lack of Sae2 and Exo1 has similar effects on sumoylation as mutants of MRX, these end resection factors likely contribute to sumoylation via ssDNA generation that permits Siz2 recruitment (Cremona et al 2012;Psakhye and Jentsch 2012;Chung and Zhao 2015). This theory does not exclude another proposal that MRX may have a direct role in recruiting the SUMO machinery, which is based on yeast two-hybrid interactions of Mre11 with SUMO, SUMO E2, and Siz2 (Chen et al 2016). Clarifying how Mre11 associates with these proteins and its direct involvement in their recruitment will provide further insight into the roles of MRX in sumoylation.…”

The deSUMOylase SENP2 coordinates homologous recombination and nonhomologous end joining by independent mechanisms

“…A major consequence of SUMOylation is the promotion of protein:protein interactions mediated by simple and short hydrophobic SUMO interaction motifs (SIMs) on proximal proteins (Song et al 2004;Hecker et al 2006;Psakhye and Jentsch 2012). In the yeast DNA damage response, a SUMO conjugation wave brought about by the interaction of the E3 SUMO ligase Siz2 with DNA and Mre11 results in modification of protein groups, thereby promoting SUMO-SIM interactions between members of those groups (Psakhye and Jentsch 2012;Jentsch and Psakhye 2013;Chen et al 2016). In humans, modification by SUMO E3 ligases PIAS1/4 (protein inhibitor of activated STAT) and CBX4 coordinate the repair response, driving the localization, activity, and stability of many signaling and repair proteins, such as RNF168, BRCA1, XRCC4, and Ku70 (Yurchenko et al 2006(Yurchenko et al , 2008Galanty et al 2009;Morris et al 2009;Li et al 2010;Danielsen et al 2012;Ismail et al 2012;Luo et al 2012;Yin et al 2012;Hang et al 2014;Lamoliatte et al 2014;Tammsalu et al 2014).…”