WRNIP1 Protects Reversed DNA Replication Forks from SLX4-Dependent Nucleolytic Cleavage
Bartlomiej Porebski1, Sebastian Wild1, Sandra Kummer1
1Institute of Molecular Cancer Research, University of Zurich, 8057 Zurich, Switzerland.
Abstract:
During DNA replication stress, stalled replication forks need to be stabilized to prevent fork collapse and genome instability. The AAA + ATPase WRNIP1 (Werner Helicase Interacting Protein 1) has been implicated in the protection of stalled replication forks from nucleolytic degradation, but the underlying molecular mechanism has remained unclear. Here we show that WRNIP1 exerts its protective function downstream of fork reversal. Unexpectedly though, WRNIP1 is not part of the well-studied BRCA2-dependent branch of fork protection but seems to protect the junction point of reversed replication forks from SLX4-mediated endonucleolytic degradation, possibly by directly binding to reversed replication forks. This function is specific to the shorter, less abundant, and less conserved variant of WRNIP1. Overall, our data suggest that in the absence of BRCA2 and WRNIP1 different DNA substrates are generated at reversed forks but that nascent strand degradation in both cases depends on the activity of exonucleases and structure-specific endonucleases.
Insights
Werner Helicase Interacting Protein 1 (WRNIP1) protects stalled DNA replication forks from degradation. This protein functions independently of BRCA2, safeguarding reversed forks from SLX4-mediated damage.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- DNA replication stress can lead to stalled replication forks, which require stabilization to prevent genome instability.
- Werner Helicase Interacting Protein 1 (WRNIP1) is known to protect stalled replication forks from nucleolytic degradation, but its mechanism is unclear.
Purpose of the Study:
- To elucidate the molecular mechanism by which WRNIP1 protects stalled replication forks.
- To determine WRNIP1's role in the context of fork reversal and its relationship with other known fork protection pathways.
Main Methods:
- Investigated WRNIP1 function downstream of replication fork reversal.
- Assessed WRNIP1's interaction with reversed replication forks and its role in preventing degradation.
- Compared WRNIP1's function with the BRCA2-dependent pathway.
Main Results:
- WRNIP1 protects reversed replication forks from SLX4-mediated degradation, acting downstream of fork reversal.
- WRNIP1 functions independently of the BRCA2-dependent fork protection pathway.
- A specific, shorter variant of WRNIP1 mediates this protective function.
- Absence of BRCA2 and WRNIP1 leads to distinct DNA substrates at reversed forks, but degradation still relies on nucleases.
Conclusions:
- WRNIP1 plays a crucial role in safeguarding reversed replication forks from specific nucleolytic degradation pathways.
- WRNIP1's mechanism of action is distinct from the well-characterized BRCA2 pathway.
- Understanding WRNIP1's function provides insights into maintaining genome stability during replication stress.
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