CRL4Wdr70 regulates H2B monoubiquitination and facilitates Exo1-dependent resection

Abstract

Double-strand breaks repaired by homologous recombination (HR) are first resected to form single-stranded DNA, which binds replication protein A (RPA). RPA attracts mediators that load the Rad51 filament to promote strand invasion, the defining feature of HR. How the resection machinery navigates nucleosome-packaged DNA is poorly understood. Here we report that in Schizosaccharomyces pombe a conserved DDB1-CUL4-associated factor (DCAF), Wdr70, is recruited to DSBs as part of the Cullin4-DDB1 ubiquitin ligase (CRL4Wdr70) and stimulates distal H2B lysine 119 mono-ubiquitination (uH2B). Wdr70 deletion, or uH2B loss, results in increased loading of the checkpoint adaptor and resection inhibitor Crb253BP1, decreased Exo1 association and delayed resection. Wdr70 is dispensable for resection upon Crb253BP1 loss, or when the Set9 methyltransferase that creates docking sites for Crb2 is deleted. Finally, we establish that this histone regulatory cascade similarly controls DSB resection in human cells.

The Antiresection Activity of the X Protein Encoded by Hepatitis Virus B

“…Both domains are indispensable in mediating the interaction of WDR70 with DDB1 (Fig. C) . Strikingly, the C terminus of WDR70 contains a similar feature to that characterized for the DDB2 sequence: an additional α‐helix adjunct to the H‐box that provides further binding capacity between DDB1 and DDB2.…”

“…The structural similarities between WDR70 and DDB2 suggest that WDR70 resembles the subclass of DCAF proteins (including DDB2) whose engagement to DDB1 through their H‐box is liable to competition by the homologous sequence of HBx . This would be consistent with the fact that knockout of human WDR70 by clustered regularly interspaced short palindromic repeats (CRISPR) in 293T cells resulted in decreased NBS1/RPA32 phosphorylation and diminished RAD51 recruitment. If HBx is influencing HR mainly through an interaction with WDR70, we would predict that expressing HBx in WDR70 knockout cells would not further decrease NBS1 or RAP32 phosphorylation.…”

“…3C). (12,30) Strikingly, the C terminus of WDR70 contains a similar feature to that characterized for the DDB2 sequence: an additional α-helix adjunct to the H-box that provides further binding capacity between DDB1 and DDB2. The presence of this conserved additional α-helix is predicted to provide extra binding capabilities for WDR70 and DDB1 ( Fig.…”

Rad6–Bre1-mediated H2B ubiquitination regulates telomere replication by promoting telomere-end resection

“…In both fission yeast and human cells, H2Bub1 has been demonstrated to facilitate DNA-end resection likely through chromatin reorganization, and thus influence HR and genome stability (41,42). In budding yeast, H2Bub1 has been shown to make the chromatin compact, and lack of H2Bub1 leads to a loose chromatin (70,71).…”

Guard the guardian: A CRL4 ligase stands watch over histone production

“…Other CRL4 ligases have been implicated in directly and indirectly mediating histone modification events, or in degradation of transcription factors, both altering the transcriptional landscape of a cell. 9,18,36,53 Additionally, CRL4s have recently received special attention as they are prone to reprogramming by exogenous factors such as drugs or viruses, thereby creating de novo ubiquitination substrates, many of which are diseaserelevant transcription factors. 25,26,40 In summary, cullin4-RING E3 ubiquitin ligases are guardians of virtually all chromatin-relevant processes and our recent findings 7 have now expanded their target range to histone production.…”