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Staurosporine-sensitive protein phosphorylation is required for postreplication DNA repair in human cells
M P Svetlova1, L V Solovjeva, A A Nikiforov
1Institute of Cytology of the Russian Academy of Sciences, St. Petersburg.
Abstract:
DNA repair is an important factor of stability of pro- and eukaryotic genomes which plays a central role in mutagenesis and carcinogenesis. Genetic control of nucleotide excision repair (NER) in mammalian cells is well studied, but little is known about molecular mechanisms of postreplication repair (PRR) which allows bypass of base lesions in template strands after DNA replication. In Saccharomyces cerevisiae PRR is controlled by the RAD61RAD18 pathway which involves POL30 gene encoding proliferating cell nuclear antigen (PCNA), and in human cells PCNA is known to be closely associated with the newly replicated chromatin where PRR probably takes place. In UV-irradiated human cells distinct PCNA foci may be detected in some cells which accumulate phosphorylated breast cancer susceptibility protein BRCA1 and another protein BARD1. Human PCNA is also known to be phosphorylated after UV-irradiation. In this study we found that the known inhibitor of protein kinases staurosporine supresses PRR in NER-deficient cells which is consistent with the view that BRCA1 and PCNA are required for PRR. We also have shown that the distinct PCNA foci in UV-irradiated NER-deficient cells are actually associated with the newly replicated chromatin. Since RAD18 protein is not essential for normal DNA replication and directly controls PRR in yeast, we analysed whether this protein as well as its human homologs (HR18A and HR18B) have common domains with BRCA1 and BARD1. It is found that HR18A has a subregion of homology to BARD1 and HR18A-to BRCA1. Taken together the results indicate that BRCA1 and BARD1 may be involved in PRR in human cells.
Insights
Postreplication repair (PRR) bypasses DNA lesions after replication. BRCA1 and BARD1 proteins, along with proliferating cell nuclear antigen (PCNA), are implicated in human PRR, suggesting a role in genome stability.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- DNA repair mechanisms are crucial for maintaining genome stability and preventing mutagenesis and carcinogenesis.
- While nucleotide excision repair (NER) is well-understood in mammals, the molecular mechanisms of postreplication repair (PRR) remain less clear.
- PRR enables bypass of DNA base lesions during replication, a process critical for accurate DNA synthesis.
Purpose of the Study:
- To investigate the role of BRCA1 and BARD1 proteins in human postreplication repair (PRR).
- To explore the association of proliferating cell nuclear antigen (PCNA) foci with newly replicated chromatin during PRR.
- To analyze potential homology between human RAD18 homologs (HR18A, HR18B) and BRCA1/BARD1.
Main Methods:
- Utilized staurosporine, a protein kinase inhibitor, to assess its effect on PRR in NER-deficient cells.
- Microscopically examined UV-irradiated NER-deficient cells to detect and characterize PCNA foci.
- Performed homology analysis between human RAD18 homologs and BRCA1/BARD1 proteins.
Main Results:
- Staurosporine suppressed PRR in NER-deficient cells, supporting the involvement of BRCA1 and PCNA.
- Distinct PCNA foci in UV-irradiated cells were localized to newly replicated chromatin.
- Homology was identified between HR18A and both BARD1 and BRCA1.
Conclusions:
- BRCA1 and BARD1 proteins are likely involved in the postreplication repair (PRR) pathway in human cells.
- PCNA foci associated with newly replicated DNA are indicative of PRR activity.
- The identified homology suggests a potential functional link between RAD18 homologs and BRCA1/BARD1 in DNA repair.