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

Abstract

Summary Structure-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.

Recruitment and positioning determine the specific role of the XPF ‐ ERCC 1 endonuclease in interstrand crosslink repair

“…The previously mentioned BTB domain and the MUS312/MEI9 interaction‐like, or MLR, domain (Fig 6C; Fekairi et al , 2009; Kim et al , 2013). To further investigate the importance of the MLR domain for the interaction with XPF, we purified xl SLX4 WT and xl SLX4 ΔMLR .…”

The XPA-binding domain of ERCC1 Is Required for Nucleotide Excision Repair but Not Other DNA Repair Pathways

“…Mus312 mutants and a Mei-9 mutant are hypersensitive to cross-linking agents but not UV irradiation, strongly suggesting a role in ICL repair (56). Recent studies have identified SLX4 as a human homolog of MUS312 (57)(58)(59)(60). SLX4 interacts with a number of endonucleases, including ERCC1-XPF, MUS81-EME1, and SLX1.…”

Fission Yeast Pxd1 Promotes Proper DNA Repair by Activating Rad16XPF and Inhibiting Dna2

“…Compared with Slx4 proteins in S. cerevisiae and metazoans, S. pombe Slx4 is much shorter and appears to have lost the region required for the interaction with XPF-ERCC1 [28]. On the other hand, the middle region of Pxd1 (residues 101–233), which mediates Rad16 binding, seems to possess sequence similarity to the XPF-binding region of metazoan Slx4 proteins, which has been referred to as the MLR (MEI9 XPF -interaction-Like Region) (Figure S5E) [28]–[30].…”

“…On the other hand, the middle region of Pxd1 (residues 101–233), which mediates Rad16 binding, seems to possess sequence similarity to the XPF-binding region of metazoan Slx4 proteins, which has been referred to as the MLR (MEI9 XPF -interaction-Like Region) (Figure S5E) [28]–[30]. Thus, we speculate that during evolution, in the lineage leading to the fission yeast, the ancestor Slx4 protein may have split into two proteins, one becoming Pxd1 and the other evolving into the current-day S. pombe Slx4, which is solely involved in the regulation of the Slx1 nuclease [31].…”