The plasticity of DNA replication forks in response to clinically relevant genotoxic stress

Human DDK rescues stalled forks and counteracts checkpoint inhibition at unfired origins to complete DNA replication

“…In addition to protecting remodeled forks, Rad51 enables fork restart via homologous recombination (Bhat and Cortez, 2018). Defects in fork protection make nascent strands vulnerable to degradation by various nucleases, but the specific requirements vary across genetic backgrounds (Berti et al, 2020;Tye et al, 2020). We did not detect a positive role for DDK in resecting stalled or collapsed Figure 5.…”

“…Current models of fork protection propose that RPA initiates fork protection via recruitment and regulation of fork remodelers, leading to fork reversal (Berti et al, 2020;Quinet et al, 2017;Tye et al, 2020). Thereafter, BRCA1 and BRCA2 recruit Rad51 and promote nucleofilament assembly (Bhat and Cortez, 2018;Rickman and Smogorzewska, 2019).…”

Limiting homologous recombination at stalled replication forks is essential for cell viability: DNA2 to the rescue

“…Reversed RFs have emerged as key intermediates for the protection of stalled RFs and the resumption of DNA synthesis by a variety of mechanisms (Neelsen and Lopes 2015). RAD51 and its primary loader in mammalian cells, BRCA2, protect the DNA end exposed at reversed RFs from degradation, maintaining them in a configuration that allows subsequent restart and/or fusion with an approaching active RF (Berti et al 2020;Schlacher et al 2011 Pardo et al 2020). Long-term exposure to replication stress is associated with the breakage of stalled RFs (Petermann et al 2010), at least in part due to the action of structure-specific nucleases (also known as Holliday-junction resolvases) (Rass 2013).…”

“…Reversed RFs have emerged as key intermediates for the protection of stalled RFs and the resumption of DNA synthesis by a variety of mechanisms (Neelsen and Lopes 2015 ). RAD51 and its primary loader in mammalian cells, BRCA2, protect the DNA end exposed at reversed RFs from degradation, maintaining them in a configuration that allows subsequent restart and/or fusion with an approaching active RF (Berti et al 2020 ; Schlacher et al 2011 ). Similarly, fork protection by Rad51 and its loader Rad52 is indispensable for replication completion upon RF-blockage in yeast (Ait Saada et al 2017 ; Pardo et al 2020 ).…”

SMARCAD1 Mediated Active Replication Fork Stability Maintains Genome Integrity

“…Here, our study shows a unique pathway of active fork stabilization mediated by SMARCAD1 which is critical for fork progression in BRCA1-deficient cells even under unperturbed conditions. This implies that SMARCAD1 mediated active replication fork stability is a central and a separate pathway for stabilization of replication forks than from recently described PRIMPOL mediated fork re-priming or well-established BRCA1-mediated fork protection pathway (56).…”