Cooperative responses of DNA-damage-activated protein kinases ATR and ATM and DNA translesion polymerases to replication-blocking DNA damage in a stem-cell niche.
Conserved DNA-damage responses (DDRs) efficiently cope with replication blocks and double-strand breaks (DSBs) in cultured eukaryotic cells; DDRs in tissues remain poorly understood. DDR-inactivating mutations lethal in animals are tolerated in Arabidopsis, whose root meristem provides a powerful stem-cell-niche model. We imaged UVB-induced death of specific meristem cells in single and double Arabidopsis mutants to elucidate cooperation among DNA translesion synthesis (TLS) polymerases (Polη, Polζ) and DNA-damage-activated protein kinases (ATR, ATM). Death was 100-fold higher in stem and progenitor (StPr) cells than in transiently amplifying cells. Quantitative analyses of dose-response plots showed that Polη and Polζ act redundantly to tolerate replication blocks and that Polζ-mediated TLS requires ATR. Deficient TLS resulted in ATM-signaled death, which first appeared 10-14h post-UVB. Although ssDNA downstream of blocks was likely cleaved into DSBs throughout S phase, death pathways appeared to initiate late in S. In atm mutants death appeared much later, likely signaled by a slow ATR-dependent pathway. To bypass replication blocks, tissues may use TLS rather than error-free pathways that could generate genomic aberrations. Dynamic balances among ATR and ATM death-avoidance and death-signaling functions determine how many DSB-burdened StPr cells are killed. Their replacement by less-burdened quiescent-center cells then restores growth homeostasis.
Department of Environmental and Molecular Toxicology, Oregon State University, 1007 ALS, Campus Way, Corvallis, OR 97331, United States.
Marc J
MJ
Curtis
John B
JB
Hays
D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D016923:Cell Death / Q000235:genetics / Q000528:radiation effects; D004249:DNA Damage; D004261:DNA Replication / Q000235:genetics* / Q000528:radiation effects; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis / Q000235:genetics / Q000528:radiation effects; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000528:radiation effects; D055153:Stem Cell Niche / Q000235:genetics* / Q000528:radiation effects; D013234:Stem Cells / Q000166:cytology / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects; D013997:Time Factors; D014466:Ultraviolet Rays; D000099270:Y-Family DNA Polymerases
D029681:Arabidopsis Proteins; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D004259:DNA-Directed DNA Polymerase; D017346:Protein Serine-Threonine Kinases; C576589:ATM protein, Arabidopsis; C576892:ATR protein, Arabidopsis; C425929:DNA polymerase zeta; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases