PKA prevents the resection of DNA double-strand breaks and favours nonhomologous end-joining.

Genome rearrangement is a hallmark of cancer and ageing. DNA double-strand breaks (DSBs) are highly toxic lesions that can generate genome rearrangements. Several pathways compete for DSB repair, and selection of the appropriate repair process is critical for genetic stability. DSB repair acts according to two steps: (1) the choice between nonhomologous end-joining (NHEJ) and the resection of DNA ends, generating single-stranded DNA (ssDNA) and (2) on generated ssDNA, homologous recombination (HR) and sub-processes. Here, we show that 53BP1, which plays a prime role in the first step by protecting against resection and fostering NHEJ, physically interacts with the catalytic subunits of cAMP-dependent protein kinase A (PKAcs). PKA favours the recruitment of 53BP1 at DNA damage sites and consistently prevents resection, favouring NHEJ. Inhibition of PKA stimulated resection and concurrently reduced NHEJ. Conversely, the activation of PKA with 8-Bromo-cAMP stimulated NHEJ and reduced HR. These data provide new avenues for potential anticancer strategies. More generally, these findings underscore the high complexity of the regulation of DSB repair, identifying PKA as a novel participant in the DNA damage response that acts in the DSB repair process, which may be essential for maintaining genome integrity.