Reducing DNA polymerase alpha in the absence of Drosophila ATR leads to P53-dependent apoptosis and developmental defects.
The ability to respond to DNA damage and incomplete replication ensures proper duplication and stability of the genome. Two checkpoint kinases, ATM and ATR, are required for DNA damage and replication checkpoint responses. In Drosophila, the ATR ortholog (MEI-41) is essential for preventing entry into mitosis in the presence of DNA damage. In the absence of MEI-41, heterozygosity for the E(mus304) mutation causes rough eyes. We found that E(mus304) is a mutation in DNApol-alpha180, which encodes the catalytic subunit of DNA polymerase alpha. We did not find any defects resulting from reducing Polalpha by itself. However, reducing Polalpha in the absence of MEI-41 resulted in elevated P53-dependent apoptosis, rough eyes, and increased genomic instability. Reducing Polalpha in mutants that lack downstream components of the DNA damage checkpoint (DmChk1 and DmChk2) results in the same defects. Furthermore, reducing levels of mitotic cyclins rescues both phenotypes. We suggest that reducing Polalpha slows replication, imposing an essential requirement for the MEI-41-dependent checkpoint for maintenance of genome stability, cell survival, and proper development. This work demonstrates a critical contribution of the checkpoint function of MEI-41 in responding to endogenous damage.
LaRocque
Jeannine R
JR
Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Dougherty
Diana L
DL
Hussain
Sumreen K
SK
Sekelsky
Jeff
J
D000818:Animals; D017209:Apoptosis; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000502:physiology; D004249:DNA Damage; D004256:DNA Polymerase I / Q000172:deficiency / Q000502:physiology*; D004268:DNA-Binding Proteins; D004330:Drosophila; D029721:Drosophila Proteins; D005128:Eye Diseases; D042822:Genomic Instability; D008297:Male; D017346:Protein Serine-Threonine Kinases; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D064007:Ataxia Telangiectasia Mutated Proteins; C444435:Mei-41 protein, Drosophila; D017346:Protein Serine-Threonine Kinases; D004256:DNA Polymerase I