Study reveals how replication protein A prevents unregulated DNA synthesis and maintains genome stability
Researchers using Xenopus egg extracts have shown that the protein Replication Protein A (RPA) actively suppresses inappropriate DNA synthesis and prevents unscheduled recruitment of recombination factors to single-stranded DNA. RPA is known to stabilize exposed single-stranded DNA during replication, recombination, and repair, and its depletion is associated with replication catastrophe. The findings clarify how RPA depletion leads to genome instability, with implications for understanding DNA damage responses and replication stress.
A new study published on bioRxiv demonstrates that Replication Protein A (RPA), the primary single-stranded DNA (ssDNA)-binding protein in eukaryotes, plays a broader protective role in genome stability than previously appreciated. Using nuclear extracts from Xenopus eggs, the researchers found that excess ssDNA triggers spontaneous DNA priming — a reaction normally suppressed in physiological conditions — and that this suppression depends on RPA binding stoichiometrically to ssDNA. Proteomic analysis of the ssDNA-binding landscape showed that RPA promotes the association of ATR checkpoint factors, DNA polymerase-primase, and the RFWD3 ubiquitin ligase with ssDNA. Conversely, when RPA is depleted, the recombination factor Rad51, its paralogs, and the helicase Fbh1 — which interacts with both RPA and Rad51 and promotes replication fork breakage under stress — are inappropriately recruited. These results suggest that RPA functions as a gatekeeper that channels ssDNA into appropriate repair or checkpoint pathways while blocking premature or unscheduled recombination and fork-processing events.
What's missing
The Xenopus egg extract system, while a well-established model, may not fully recapitulate RPA dynamics in somatic human cells. The study does not address whether the observed effects of RPA depletion are reversible or how they relate quantitatively to RPA exhaustion levels seen in human disease contexts such as cancer or viral infection.
What different sources said
- bioRxivCenter
Replication protein A prevents unregulated priming and Rad51 loading on single-stranded DNA in nuclear extracts of Xenopus eggs
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