Abstract
Although homologous recombination (HR) is indicated as a high-fidelity repair mechanism, break-induced replication (BIR), a subtype of HR, is a mutagenic mechanism that leads to chromosome rearrangements. It remains poorly understood how cells suppress mutagenic BIR. Trapping of Topoisomerase 1 by camptothecin (CPT) in a cleavage complex on the DNA can be transformed into single-ended double-strand breaks (seDSBs) upon DNA replication or colliding with transcriptional machinery. Here, we demonstrate a role of Abraxas in limiting seDSBs undergoing BIR-dependent mitotic DNA synthesis. Through counteracting K63-linked ubiquitin modification, Abraxas restricts SLX4/Mus81 recruitment to CPT damage sites for cleavage and subsequent resection processed by MRE11 endonuclease, CtIP, and DNA2/BLM. Uncontrolled SLX4/MUS81 loading and excessive end resection due to Abraxas-deficiency leads to increased mitotic DNA synthesis via RAD52- and POLD3- dependent, RAD51-independent BIR and extensive chromosome aberrations. Our work implicates Abraxas/BRCA1-A complex as a critical regulator that restrains BIR for protection of genome stability.
Highlights
Homologous recombination (HR) is indicated as a high-fidelity repair mechanism, break-induced replication (BIR), a subtype of homologous recombination (HR), is a mutagenic mechanism that leads to chromosome rearrangements
We found that when treated with CPT, Abraxas knockout (KO) U2OS cells or Abraxas null (−/−) mouse embryonic fibroblast (MEF) cells displayed increased phosphorylation of RPA32 S4/8, a surrogate marker of singlestranded DNA (ssDNA) accumulation and DNA end resection, upon treatment and at the indicated times after release into fresh media when compared to the control cells (Fig. 1a and Supplementary Fig. 1a)
In the absence of Abraxas, increased K63-linked ubiquitin conjugation leads to SLX4/MUS81 overloading on chromatin, generating increased single-ended double-strand breaks (seDSBs), which are further processed by MRE11 endonucleases, CTIP and DNA2/BLM, forming an extensive length of ssDNA
Summary
Homologous recombination (HR) is indicated as a high-fidelity repair mechanism, break-induced replication (BIR), a subtype of HR, is a mutagenic mechanism that leads to chromosome rearrangements. Trapping of Topoisomerase 1 by camptothecin (CPT) in a cleavage complex on the DNA can be transformed into single-ended double-strand breaks (seDSBs) upon DNA replication or colliding with transcriptional machinery. Replication forks colliding with the stabilized TOP1ccs induce replication-associated DNA double-strand breaks (DSBs) These are single-ended DSBs (seDSBs) caused by either replication runoff or cleavage of stalled replication forks by MUS814. It has been established that seDSBs repair undergo break-induced replication (BIR), a type of HR process that involves extensive 5′ to 3′-end resection to generate a 3′-singlestranded DNA (ssDNA) end that is bound by RPA, RAD52-
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
