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Sumoylation of Smc5 Promotes Error-free Bypass at Damaged Replication Forks
Mariel Zapatka1, Irene Pociño-Merino1, Hayat Heluani-Gahete2
1Departament de Ciencies Mediques Basiques, Institut de Recerca Biomedica de Lleida, Universitat de Lleida, 25198 Lleida, Spain.
Abstract:
Replication of a damaged DNA template can threaten the integrity of the genome, requiring the use of various mechanisms to tolerate DNA lesions. The Smc5/6 complex, together with the Nse2/Mms21 SUMO ligase, plays essential roles in genome stability through undefined tasks at damaged replication forks. Various subunits within the Smc5/6 complex are substrates of Nse2, but we currently do not know the role of these modifications. Here we show that sumoylation of Smc5 is targeted to its coiled-coil domain, is upregulated by replication fork damage, and participates in bypass of DNA lesions. smc5-KR mutant cells display defects in formation of sister chromatid junctions and higher translesion synthesis. Also, we provide evidence indicating that Smc5 sumoylation modulates Mph1-dependent fork regression, acting synergistically with other pathways to promote chromosome disjunction. We propose that sumoylation of Smc5 enhances physical remodeling of damaged forks, avoiding the use of a more mutagenic tolerance pathway.
Insights
The Smc5/6 complex and Nse2/Mms21 SUMO ligase are crucial for genome stability. Sumoylation of Smc5 at damaged replication forks aids DNA lesion bypass and fork remodeling, preventing mutagenic tolerance pathways.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Genome integrity is threatened by damaged DNA replication.
- The Smc5/6 complex and Nse2/Mms21 SUMO ligase are vital for genome stability at replication forks.
- The precise roles of Smc5/6 subunit modifications by Nse2 remain unclear.
Purpose of the Study:
- To investigate the role of Smc5 sumoylation in DNA damage tolerance.
- To elucidate the function of Nse2-mediated sumoylation of the Smc5/6 complex at damaged replication forks.
Main Methods:
- Characterization of Smc5 sumoylation site and regulation.
- Analysis of smc5-KR mutant phenotypes related to DNA repair.
- Investigating the interplay between Smc5 sumoylation and Mph1-dependent fork regression.
Main Results:
- Sumoylation of Smc5 occurs at its coiled-coil domain and is upregulated by replication fork damage.
- Smc5 sumoylation is essential for efficient bypass of DNA lesions.
- smc5-KR mutants exhibit defects in sister chromatid junction formation and increased translesion synthesis.
- Smc5 sumoylation modulates Mph1-dependent fork regression, promoting chromosome segregation.
Conclusions:
- Sumoylation of Smc5 enhances physical remodeling of damaged replication forks.
- This modification promotes a less mutagenic DNA damage tolerance pathway.
- The Smc5/6-Nse2 axis plays a critical role in maintaining genome stability during replication stress.
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