A replication stress safeguard provided by the Elg1 Replication Factor C-like complex
- PMID: 40985265
- DOI: 10.1093/genetics/iyaf196
A replication stress safeguard provided by the Elg1 Replication Factor C-like complex
Abstract
The Elg1 Replication Factor C-like complex (Elg1-RLC) that functions as a PCNA unloader, is known to be involved in multiple DNA replication/repair-related activities from yeast to humans. By exploiting disassembly-prone PCNA mutants, we reveal that Elg1-RLC uses its PCNA unloading activity to counter the DNA-alkylating agent methyl-methanesulfonate (MMS)-mediated slow progression of replication forks. Despite having a largely functional DNA Damage Response (DDR), the viability loss of elg1Δ-DDR double mutants, in the presence of MMS, matches that of mec1Δ and rad53Δ cells, deficient for the central checkpoint kinases. This suggests that elg1Δ-DDR double mutants experience replication fork collapse when exposed to MMS. Indeed, in response to MMS, accumulation of Rad52 foci in the replicative elg1Δ-DDR cells supports this possibility. However, the failure of rescuing elg1Δ-DDR mutants by elevating dNTP levels (by deleting the ribonucleotide reductase SML1) eliminates the possibility of a Rad53-regulated dNTP shortage-mediated fork collapse. Thus, we propose a S-phase checkpoint regulatory role of Elg1-RLC that works through a noncanonical pathway parallel to the canonical one. Collectively, our findings suggest a model in which Elg1-RLC, by timely unloading chromatin-bound PCNA from the damaged/stalled forks, coordinates the DDR pathways to safeguard the integrity of replication forks under replication stress.
Keywords: 9-1-1/Rad24; DDR sensors/mediators; DNA Damage Response (DDR); Elg1; MMS; Mec1/Rad53; PCNA; replication forks; replication stress.
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