ATR suppresses apoptosis after UVB irradiation by controlling both translesion synthesis and alternative tolerance pathways.
Ultraviolet (UV) light can stall replication forks owing to the formation of bulky lesions in the DNA. Replication across these blocking lesions occurs through translesion DNA synthesis, and cells activate the ATR damage responses to UV. However, it remains unclear whether lesion bypass requires the replication checkpoint because ATR is not necessary for PCNA ubiquitylation. We observed that ATR knockdown by siRNA increased replication stress and promoted early induction of apoptosis following UVB irradiation in SV40-immortalized human cells, including cells from XP-V and XP-C patients. XP-V cells were further sensitized by the silencing, indicating that DNA polymerase η (Pol η) remains active despite ATR control. However, following UVB irradiation, ATR-depleted cells were unable to achieve mitosis, as would be expected after the loss of a DNA checkpoint control. Thus, ATR also regulates replication arrest recovery following UVB-induced damage, independently of Pol η, in SV40-immortalized cell lines. The ATR-mediated DNA damage response regulates replication and different tolerance pathways, and in these cells, ATR depletion induces replication catastrophe, which contributes to explain the potential of ATR inhibition to protect against UVB-induced carcinogenesis.
Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-000, Brazil.
Leonardo C
LC
Andrade-Lima
Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-000, Brazil.
Luciana N
LN
Andrade
Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-000, Brazil cfmmenck@usp.br.
Carlos F M
CF
Menck
D017209:Apoptosis / Q000528:radiation effects*; D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000235:genetics / Q000528:radiation effects*; D002461:Cell Line, Transformed; D004249:DNA Damage; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D014466:Ultraviolet Rays / Q000009:adverse effects*; D000099270:Y-Family DNA Polymerases
D064007:Ataxia Telangiectasia Mutated Proteins; D004259:DNA-Directed DNA Polymerase; C576597:ATR protein, human; C546205:POLN protein, human; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases
ATR; Cell cycle progression; DNA damage response; Replication arrest; Translesion synthesis; UVB light