During carcinogenesis, cells are exposed to increased replication stress due to replication fork arrest at sites of DNA lesions and difficult to replicate genomic regions. Efficient fork restart and DNA repair are important for cancer cell proliferation. We previously showed that the ADP-ribosyltransferase PARP10 interacts with the replication protein proliferating cell nuclear antigen and promotes lesion bypass by recruiting specialized, non-replicative DNA polymerases. Here, we show that PARP10 is overexpressed in a large proportion of human tumors. To understand the role of PARP10 in cellular transformation, we inactivated PARP10 in HeLa cancer cells by CRISPR/Cas9-mediated gene knockout, and overexpressed it in non-transformed RPE-1 cells. We found that PARP10 promotes cellular proliferation, and its overexpression alleviates cellular sensitivity to replication stress and fosters the restart of stalled replication forks. Importantly, mouse xenograft studies showed that loss of PARP10 reduces the tumorigenesis activity of HeLa cells, while its overexpression results in tumor formation by non-transformed RPE-1 cells. Our findings indicate that PARP10 promotes cellular transformation, potentially by alleviating replication stress and suggest that targeting PARP10 may represent a novel therapeutic approach.

DNA repair mechanisms such as Nucleotide Excision Repair (NER) and Translesion Synthesis (TLS) are dependent on proliferating cell nuclear antigen (PCNA), a DNA polymerase accessory protein. Recently, homozygosity for p.Ser228Ile mutation in the PCNA gene was reported in patients with neurodegeneration and impaired NER. Using exome sequencing we identified a homozygous deleterious mutation, c.648delAG, in the PARP10 gene, in a patient suffering from infantile neurodegeneration. In agreement, PARP10 protein was absent from the patient cells. We have previously shown that PARP10 is recruited by PCNA to DNA damage sites and is required for DNA damage resistance. The patient cells were significantly more sensitive to hydroxyurea and UV-induced DNA damage than control cells, resulting in increased apoptosis, indicating DNA repair impairment in the patient cells. PARP10 deficiency joins the long list of DNA repair defects associated with neurodegenerative disorders, including ataxia telangiectasia, xeroderma pigmentosum, Cockayne syndrome and the recently reported PCNA mutation.

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