DNA-PKcs, ATM, and ATR Interplay Maintains Genome Integrity during Neurogenesis

Abstract

The DNA damage response (DDR) orchestrates a network of cellular processes that integrates cell-cycle control and DNA repair or apoptosis, which serves to maintain genome stability. DNA-PKcs (the catalytic subunit of the DNA-dependent kinase, encoded by PRKDC), ATM (ataxia telangiectasia, mutated), and ATR (ATM and Rad3-related) are related PI3K-like protein kinases and central regulators of the DDR. Defects in these kinases have been linked to neurodegenerative or neurodevelopmental syndromes. In all cases, the key neuroprotective function of these kinases is uncertain. It also remains unclear how interactions between the three DNA damageresponsive kinases coordinate genome stability, particularly in a physiological context. Here, we used a genetic approach to identify the neural function of DNA-PKcs and the interplay between ATM and ATR during neurogenesis. We found that DNA-PKcs loss in the mouse sensitized neuronal progenitors to apoptosis after ionizing radiation because of excessive DNA damage. DNA-PKcs was also required to prevent endogenous DNA damage accumulation throughout the adult brain. In contrast, ATR coordinated the DDR during neurogenesis to direct apoptosis in cycling neural progenitors, whereas ATM regulated apoptosis in both proliferative and noncycling cells. We also found that ATR controls a DNA damage-induced G 2 /M checkpoint in cortical progenitors, independent of ATM and DNA-PKcs. These nonoverlapping roles were further confirmed via sustained murine embryonic or cortical development after all three kinases were simultaneously inactivated. Thus, our results illustrate how DNA-PKcs, ATM, and ATR have unique and essential roles during the DDR, collectively ensuring comprehensive genome maintenance in the nervous system.

Impact of DNA repair and stability defects on cortical development

“…Genome surveillance is ensured by three PI3K-like protein kinases: ATM (ataxia-telangiectasia, mutated), ATR (ATM and Rad3related) and PRKDC (the catalytic subunit of the DNA-dependent protein kinase) [23]. The relative importance of individual kinases in CNS development is dependent on the type of DNA lesion and cells [36]. ATR exerts a prominent role in protecting cells from DNA damage arising during S-phase in consequence of DNA stressors like ultraviolet radiation, DNA polymerase inhibitors, nucleotide depletion or DNA crosslinkers, leading to DNA polymerase slowing or stalling [23].…”

“…However, NHEJ core components inactivation leads to extensive neural apoptosis and embryonic lethality, while mice lacking PRKDC are viable [41] [42]. How these three kinases collectively organise the responses to DNA damage has been elegantly demonstrated by Enriquez-Rios and colleagues: mice bearing single or combined mutations of Atm, Atr or Prkdc showed differential cellular sensitivity in response to IR [36]. Authors confirmed that ATM transduces pro-apoptotic signals in non-cycling cells, while it turned out to be less important in replicating progenitors in VZ.…”

Genetic interaction between DNA repair factors PAXX, XLF, XRCC4 and DNA‐PKcs in human cells

“…Genetic interactions between ATM and the XRCC4 paralogues in HAP1 cells ATM and DNA-PKcs belong to the same family of protein kinases [33]. To determine the genetic interactions between ATM and the XRCC4 paralogues in human cells, we first exposed DNA-PKcs Δ (Fig.…”

ATRIP protects progenitor cells against DNA damagein vivo

“…Although we did not determine which kinase was activated following ATRIP loss, our findings are consistent with the formation of DSBs and activation of ATM or DNA-PK or both. Nevertheless, it was shown that even of absence of the three main DDR kinases (ATM, ATR and DNA-PK), γH2AX phosphorylation and TRP53 activation are still detected, therefore we cannot exclude alternative pathways 41 .…”