Unrepaired base excision repair intermediates in template DNA strands trigger replication fork collapse and PARP inhibitor sensitivity

Author(s):Show less -

Serrano-Benitez, Almudena ; Wells, Sophie E. ; Drummond-Clarke, Lylah ; Russo, Lilian C. ; Thomas, John Christopher ; Leal, Giovanna A. ; Farrow, Mark ; Edgerton, James Michael ; Balasubramanian, Shankar ; Yang, Ming ; Frezza, Christian ; Gautam, Amit ; Brazina, Jan ; Burdova, Kamila ; Hoch, Nicolas C. ; Jackson, Stephen P. ; Caldecott, Keith W.

• Document type: Journal article
• Source: EMBO Journal; v. 42, n. 18, p. 19-pg., 2023-07-26.

Abstract

DNA single-strand breaks (SSBs) disrupt DNA replication and induce chromosome breakage. However, whether SSBs induce chromosome breakage when present behind replication forks or ahead of replication forks is unclear. To address this question, we exploited an exquisite sensitivity of SSB repair-defective human cells lacking PARP activity or XRCC1 to the thymidine analogue 5-chloro-2 & PRIME;-deoxyuridine (CldU). We show that incubation with CldU in these cells results in chromosome breakage, sister chromatid exchange, and cytotoxicity by a mechanism that depends on the S phase activity of uracil DNA glycosylase (UNG). Importantly, we show that CldU incorporation in one cell cycle is cytotoxic only during the following cell cycle, when it is present in template DNA. In agreement with this, while UNG induces SSBs both in nascent strands behind replication forks and in template strands ahead of replication forks, only the latter trigger fork collapse and chromosome breakage. Finally, we show that BRCA-defective cells are hypersensitive to CldU, either alone and/or in combination with PARP inhibitor, suggesting that CldU may have clinical utility. (AU)

• FAPESP's process: 18/18007-5 - Protein ADP-ribosylation: DNA damage signalling and impacts on human health
• Grantee: Nicolas Carlos Hoch
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 19/06039-2 - EMU awarded in the process 2018/18007-5: TissueFAXS microscope
• Grantee: Nicolas Carlos Hoch
• Support Opportunities: Multi-user Equipment Program