Drosophila melanogaster MNK/Chk2 and p53 Regulate Multiple DNA Repair and Apoptotic Pathways following DNA Damage

Abstract

We have used genetic and microarray analysis to determine how ionizing radiation (IR) induces p53-dependent transcription and apoptosis in Drosophila melanogaster. IR induces MNK/Chk2-dependent phosphorylation of p53 without changing p53 protein levels, indicating that p53 activity can be regulated without an Mdm2-like activity. In a genome-wide analysis of IR-induced transcription in wild-type and mutant embryos, all IR-induced increases in transcript levels required both p53 and the Drosophila Chk2 homolog MNK. Proapoptotic targets of p53 include hid, reaper, sickle, and the tumor necrosis factor family member Eiger. Overexpression of Eiger is sufficient to induce apoptosis, but mutations in Eiger do not block IR-induced apoptosis. Animals heterozygous for deletions that span the reaper, sickle, and hid genes exhibited reduced IR-dependent apoptosis, indicating that this gene complex is haploinsufficient for induction of apoptosis. Among the genes in this region, hid plays a central, dosage-sensitive role in IR-induced apoptosis. p53 and MNK/Chk2 also regulate DNA repair genes, including two components of the nonhomologous end-joining repair pathway, Ku70 and Ku80. Our results indicate that MNK/Chk2-dependent modification of Drosophila p53 activates a global transcriptional response to DNA damage that induces error-prone DNA repair as well as intrinsic and extrinsic apoptosis pathways.

M.H.B. was supported by fellowships from the American Cancer Society and the Alameda Cancer League and by a Worcester Foundation for Biomedical Research Annual Research Fund Innovation Grant.

We thank Isao Oishi for the generous gift of anti-MNK antibody, Ling Hong for providing cDNA libraries, and Anne Laurencon and Scott Hawley for providing the mei-41^29D allele prior to publication. We thank Kristin White, Hermann Steller, and the Bloomington Stock Center for providing Drosophila stocks. We thank Elaine Kwan for isolation of anti-p53 monoclonal antibodies and Stephen Davis and Paul Spellman for assistance with microarray data analysis.