Cockayne syndrome group B protein regulates fork restart, fork progression and MRE11-dependent fork degradation in BRCA1/2-deficient cells

• Published in: Nucleic acids research Vol. 49; no. 22; pp. 12836 - 12854
• Main Authors: Batenburg, Nicole L, Mersaoui, Sofiane Y, Walker, John R, Coulombe, Yan, Hammond-Martel, Ian, Wurtele, Hugo, Masson, Jean-Yves, Zhu, Xu-Dong
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 16.12.2021
• Subjects: BRCA1 Protein - deficiency; BRCA1 Protein - genetics; BRCA1 Protein - metabolism; BRCA2 Protein - deficiency; BRCA2 Protein - genetics; BRCA2 Protein - metabolism; Cell Line; Cell Line, Tumor; DNA - chemistry; DNA - genetics; DNA - metabolism; DNA Breaks, Double-Stranded; DNA Helicases - genetics; DNA Helicases - metabolism; DNA Repair; DNA Repair Enzymes - genetics; DNA Repair Enzymes - metabolism; DNA Replication - genetics; Genome Integrity, Repair and; HCT116 Cells; HEK293 Cells; Humans; MRE11 Homologue Protein - genetics; MRE11 Homologue Protein - metabolism; Mutation; Poly-ADP-Ribose Binding Proteins - genetics; Poly-ADP-Ribose Binding Proteins - metabolism; RNA Interference
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkab1173

Abstract Cockayne syndrome group B (CSB) protein has been implicated in the repair of a variety of DNA lesions that induce replication stress. However, little is known about its role at stalled replication forks. Here, we report that CSB is recruited to stalled forks in a manner dependent upon its T1031 phosphorylation by CDK. While dispensable for MRE11 association with stalled forks in wild-type cells, CSB is required for further accumulation of MRE11 at stalled forks in BRCA1/2-deficient cells. CSB promotes MRE11-mediated fork degradation in BRCA1/2-deficient cells. CSB possesses an intrinsic ATP-dependent fork reversal activity in vitro, which is activated upon removal of its N-terminal region that is known to autoinhibit CSB’s ATPase domain. CSB functions similarly to fork reversal factors SMARCAL1, ZRANB3 and HLTF to regulate slowdown in fork progression upon exposure to replication stress, indicative of a role of CSB in fork reversal in vivo. Furthermore, CSB not only acts epistatically with MRE11 to facilitate fork restart but also promotes RAD52-mediated break-induced replication repair of double-strand breaks arising from cleavage of stalled forks by MUS81 in BRCA1/2-deficient cells. Loss of CSB exacerbates chemosensitivity in BRCA1/2-deficient cells, underscoring an important role of CSB in the treatment of cancer lacking functional BRCA1/2.