Human SLX4 Is a Holliday Junction Resolvase Subunit that Binds Multiple DNA Repair/Recombination Endonucleases

Abstract

SummaryStructure-specific endonucleases resolve DNA secondary structures generated during DNA repair and recombination. The yeast 5′-flap endonuclease Slx1-Slx4 has received particular attention with the finding that Slx4 has Slx1-independent key functions in genome maintenance. Although Slx1 is a highly conserved protein in eukaryotes, no orthologs of Slx4 were reported other than in fungi. Here we report the identification of Slx4 orthologs in metazoa, including fly MUS312, essential for meiotic recombination, and human BTBD12, an ATM/ATR checkpoint kinase substrate. Human SLX1-SLX4 displays robust Holliday junction resolvase activity in addition to 5′-flap endonuclease activity. Depletion of SLX1 and SLX4 results in 53BP1 foci accumulation and H2AX phosphorylation as well as cellular hypersensitivity to MMS. Furthermore, we show that SLX4 binds the XPF and MUS81 subunits of the XPF-ERCC1 and MUS81-EME1 endonucleases and is required for DNA interstrand crosslink repair. We propose that SLX4 acts as a docking platform for multiple structure-specific endonucleases.

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

“…On the other hand, MUS81-mediated processing of Holliday junctions (HJs), generated during recombinational DNA repair, is upregulated at the onset of mitosis (Gallo-Fernandez et al, 2012;Matos et al, 2011;Matos et al, 2013;Szakal and Branzei, 2013;Wyatt et al, 2013). CDK1-dependent interaction with the scaffold protein SLX4 coordinates the nickase activity of another structure-selective nuclease, SLX1, with subsequent HJ incision by MUS81 (Castor et al, 2013;Fekairi et al, 2009;Gritenaite et al, 2014;Matos et al, 2011;Svendsen et al, 2009;Wyatt et al, 2013). Hence, regulated activation of MUS81 at the G2/M transition could provide an alternative explanation for its limited ability to cleave RFs during S-phase, while efficiently processing stalled replication intermediates at the onset of mitosis.…”

Fanconi anemia: a model disease for studies on human genetics and advanced therapeutics

“…BTBD12/SLX4 provides a platform for several endonucleases involved in ICL repair, including ERCC4-ERCC1, MUS81-EME1, and SLX1 that dock to cleave DNA flaps, replication forks, and Holliday junctions [46][47][48]. SLX4 is mutated in patients with bona fide FA (FANCP) [2,20].…”

The role of DNA exonucleases in protecting genome stability and their impact on ageing

“…At least one of these incisions is catalysed by MUS81-EME1, a heterodimeric endonuclease (Ciccia et al 2003) that can cleave branched structures and resolve Holliday junctions (Chen et al 2001b). It is possible that MUS81-EME1 may also make the second incision, though the excision repair factor XPF-ERCC1 is another candidate (Fekairi et al 2009). Alternatively, the structure arising from the first incision may resemble a 5′ flap, which could act as a substrate for the endonuclease activity of FAN1.…”