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Cell Type Specific Suppression of Hyper-Recombination by Human RAD18 Is Linked to Proliferating Cell Nuclear Antigen
Colette B Rogers1, Wendy Leung1, Ryan M Baxley1
1Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
Biomolecules
|January 25, 2025
Summary
RAD18, a DNA repair protein, suppresses excessive DNA recombination in some human cells. Its absence causes hyper-recombination, linked to PCNA ubiquitination, not SUMOylation.
Area of Science:
- Molecular Biology
- Genetics
- DNA Repair Mechanisms
Background:
- RAD18 is a crucial E3 ubiquitin ligase involved in maintaining genome stability.
- Its role in regulating homologous recombination (HR) in mammalian cells remains debated.
- RAD18 participates in DNA synthesis and repair pathways at replication forks.
Purpose of the Study:
- To investigate the role of RAD18 in homologous recombination (HR) in human cell lines.
- To determine if RAD18's function in HR is linked to PCNA K164 ubiquitination or SUMOylation.
- To clarify the consensus on RAD18's contribution to HR in mammalian systems.
Main Methods:
- Analysis of three independent RAD18-null human cell lines (HCT116, hTERT RPE-1, DLD1).
- Assessment of sister chromatid exchange, gene conversion, and gene targeting rates.
- Examination of PCNA K164 ubiquitination and UBC9 knockdown to assess SUMOylation.
Main Results:
- RAD18-null HCT116 cells exhibited significantly elevated recombination (hyper-recombinogenic), unlike other cell lines.
- This hyper-recombination phenotype correlated with RAD18's role in PCNA K164 ubiquitination.
- Preventing PCNA K164 SUMOylation did not impact recombination rates, highlighting ubiquitination's importance.
Conclusions:
- RAD18's requirement for suppressing hyper-recombination is cell-type dependent, influenced by intrinsic repair hierarchies.
- This function is specifically tied to RAD18-mediated PCNA K164 ubiquitination.
- The study clarifies RAD18's complex role in DNA repair and genome stability.
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