DNA-PKcs parylation regulates DNA-PK kinase activity in the DNA damage response

Abstract

DNA- dependent protein kinase catalytic subunit (-PKcs) is the core protein involved in the non-homologous end-joining repair of double-strand breaks. In addition, it can form a complex with poly(AD P-ribose) polymerase 1 (PAR P1), which catalyzes protein PAR ylation. However, it is unclear how DNA- PKcs interacts with PAR P1 in the DNA damage response and how PAR ylation affects DNA- PK kinase activity. Using immunoprecipitation, immunofluorescence and flow cytometry the present study found that DNA-PKcs was PAR ylated after DNA damage, and the PAR P1/2 inhibitor olaparib completely abolished DNA- PKcs PAR ylation. Olaparib treatment prevented DNA- PKcs protein detachment from chromatin after DNA damage and maintained DNA- PK activation, as evidenced by DNA- PKcs Ser2056 phosphorylation. Furthermore, olaparib treatment synergized with DNA- PK inhibition to suppress cell survival. All of the above results are suggestive of the important role of DNA- PKcs PAR ylation in regulating DNA- PK activity.