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Published on: April 28, 2021
Disease-associated DNA2 nuclease-helicase protects cells from lethal chromosome under-replication
Benoît Falquet1,2, Gizem Ölmezer1,2, Franz Enkner1
1Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland.
Abstract:
DNA2 is an essential nuclease-helicase implicated in DNA repair, lagging-strand DNA synthesis, and the recovery of stalled DNA replication forks (RFs). In Saccharomyces cerevisiae, dna2Δ inviability is reversed by deletion of the conserved helicase PIF1 and/or DNA damage checkpoint-mediator RAD9. It has been suggested that Pif1 drives the formation of long 5'-flaps during Okazaki fragment maturation, and that the essential function of Dna2 is to remove these intermediates. In the absence of Dna2, 5'-flaps are thought to accumulate on the lagging strand, resulting in DNA damage-checkpoint arrest and cell death. In line with Dna2's role in RF recovery, we find that the loss of Dna2 results in severe chromosome under-replication downstream of endogenous and exogenous RF-stalling. Importantly, unfaithful chromosome replication in Dna2-mutant cells is exacerbated by Pif1, which triggers the DNA damage checkpoint along a pathway involving Pif1's ability to promote homologous recombination-coupled replication. We propose that Dna2 fulfils its essential function by promoting RF recovery, facilitating replication completion while suppressing excessive RF restart by recombination-dependent replication (RDR) and checkpoint activation. The critical nature of Dna2's role in controlling the fate of stalled RFs provides a framework to rationalize the involvement of DNA2 in Seckel syndrome and cancer.
Insights
DNA2 is crucial for DNA replication fork recovery. Its absence causes chromosome under-replication, exacerbated by PIF1, highlighting DNA2
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- DNA2 is an essential nuclease-helicase involved in DNA repair and replication.
- Its absence leads to inviability, which can be rescued by deleting PIF1 or RAD9.
- Pif1 is proposed to promote 5'-flap accumulation during Okazaki fragment maturation, with Dna2 removing these intermediates.
Purpose of the Study:
- To investigate the essential function of DNA2 in replication fork (RF) recovery.
- To elucidate the interplay between Dna2, Pif1, and the DNA damage checkpoint in maintaining genome stability.
- To understand the role of DNA2 in chromosome replication and its implications for diseases like Seckel syndrome and cancer.
Main Methods:
- Utilized Saccharomyces cerevisiae as a model organism.
- Investigated the effects of dna2Δ mutations, alone and in combination with pif1Δ and rad9Δ.
- Analyzed chromosome under-replication and DNA damage checkpoint activation in response to RF stalling.
Main Results:
- Loss of Dna2 leads to severe chromosome under-replication downstream of stalled RFs.
- Pif1 exacerbates unfaithful chromosome replication in Dna2-mutant cells by triggering the DNA damage checkpoint.
- Pif1 promotes homologous recombination-coupled replication, contributing to checkpoint activation.
Conclusions:
- DNA2 is essential for promoting RF recovery and replication completion.
- DNA2 suppresses excessive recombination-dependent replication (RDR) and checkpoint activation at stalled RFs.
- DNA2's role in controlling stalled RF fate provides a rationale for its involvement in Seckel syndrome and cancer.
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02:31Homologous Recombination
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