MUS81-EME2 Promotes Replication Fork Restart

Abstract

SummaryReplication forks frequently stall at regions of the genome that are difficult to replicate or contain lesions that cause replication blockage. An important mechanism for the restart of a stalled fork involves endonucleolytic cleavage that can lead to fork restoration and replication progression. Here, we show that the structure-selective endonuclease MUS81-EME2 is responsible for fork cleavage and restart in human cells. The MUS81-EME2 protein, whose actions are restricted to S phase, is also responsible for telomere maintenance in telomerase-negative ALT (Alternative Lengthening of Telomeres) cells. In contrast, the G2/M functions of MUS81, such as the cleavage of recombination intermediates and fragile site expression, are promoted by MUS81-EME1. These results define distinct and temporal roles for MUS81-EME1 and MUS81-EME2 in the maintenance of genome stability.

A Mechanism for Controlled Breakage of Under-replicated Chromosomes during Mitosis

“…Yet, several studies established that it involves MUS81, a structure-selective endonuclease with important roles in the metabolism of replication intermediates (Beck et al, 2012;Dominguez-Kelly et al, 2011;Forment et al, 2011;Kim et al, 2013;Neelsen et al, 2013;Techer et al, 2016). In mammals, MUS81 forms heterodimeric complexes with the non-catalytic subunits EME1 or EME2 (Pepe and West, 2014a). Both MUS81-EME1 and MUS81-EME2 are capable of cleaving Y-shaped duplex DNAs in vitro, suggesting that RFs may be physiological MUS81 substrates in vivo (Pepe and West, 2014b).…”

The Structure-Specific Endonucleases MUS81 and SEND1 Are Essential for Telomere Stability in Arabidopsis

“…The mus81 mutant in the yeast S. cerevisiae shows sensitivity to agents causing replication stress and chromosome mis-segregation, which is not exclusively due to the role of Mus81 in processing HJ, as demonstrated by only partial suppression of the phenotype in the absence of Rad51 (Ho et al, 2010;Agmon et al, 2011). In mammalian cells, the generation of MUS81-dependent double-strand DNA breaks after inhibition of replication by HU or aphidicolin suggests that collapsed or stalled replication fork are processed into DNA DSB by MUS81 (Hanada et al, 2007;Pepe and West, 2014). HeLa cells depleted in the RecQ helicase WRN (Werner syndrome ATP-dependent helicase) accumulate DSB in a MUS81-dependent manner after HU treatment.…”

“…However, simultaneous depletion of WRN and RAD51 does not suppress these DSBs, suggesting that MUS81 operates upstream of RAD51 in the processing of toxic replication intermediates (Franchitto et al, 2008;Murfuni et al, 2012;Murfuni et al, 2013). Furthermore, MUS81 also plays a role in the cleavage of RFs remaining at later (G2/M) stages of the cell cycle at common fragile sites, and its absence leads to an increase in anaphase bridges due to improper disjunction of sister chromatids (Naim et al, 2013;Ying et al, 2013;Pepe and West, 2014). Much less is known about the potential role of GEN1/Yen1 in facilitating replication of difficult to replicate regions, although both yeast and mammalian cells lacking MUS81 and GEN1/Yen1 show increased genome instability compared with the corresponding single mutants (Ho et al, 2010;Agmon et al, 2011;Wyatt et al, 2013).…”

SLX4-SLX1 Protein-independent Down-regulation of MUS81-EME1 Protein by HIV-1 Viral Protein R (Vpr)

“…The C-terminal regions of EME1 (total of 570 residues) and EME2 (total of 379 residues) are highly homologous with more than 60% sequence similarity in human (43,44). Multiple studies have suggested that these complexes are involved in maintenance of genomic stability and damaged DNA processing (43)(44)(45)(46)(47). Purified recombinant MUS81-EME1 recognizes and preferentially cleaves several DNA structures, including 3Ј-flap, aberrant replication forks, and nicked Holliday junctions (45,48).…”