Human CtIP Mediates Cell Cycle Control of DNA End Resection and Double Strand Break Repair

• Published in: The Journal of biological chemistry 2009-04, Vol.284 (14), p.9558-9565
• Main Authors: Huertas, Pablo, Jackson, Stephen P.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Cycle - drug effects; Cell Line, Tumor; Conserved Sequence; Cyclin-Dependent Kinases - antagonists & inhibitors; Cyclin-Dependent Kinases - metabolism; DNA - genetics; DNA - metabolism; DNA Damage - genetics; DNA Repair - genetics; Endodeoxyribonucleases; Genomic Instability; Humans; Molecular Sequence Data; Mutation - genetics; Nuclear Proteins - chemistry; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Protein Kinase Inhibitors - pharmacology; Sequence Alignment
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M808906200

In G0 and G1, DNA double strand breaks are repaired by nonhomologous end joining, whereas in S and G2, they are also repaired by homologous recombination. The human CtIP protein controls double strand break (DSB) resection, an event that occurs effectively only in S/G2 and that promotes homologous recombination but not non-homologous end joining. Here, we mutate a highly conserved cyclin-dependent kinase (CDK) target motif in CtIP and reveal that mutating Thr-847 to Ala impairs resection, whereas mutating it to Glu to mimic constitutive phosphorylation does not. Moreover, we show that unlike cells expressing wild-type CtIP, cells expressing the Thr-to-Glu mutant resect DSBs even after CDK inhibition. Finally, we establish that Thr-847 mutations to either Ala or Glu affect DSB repair efficiency, cause hypersensitivity toward DSB-generating agents, and affect the frequency and nature of radiation-induced chromosomal rearrangements. These results suggest that CDK-mediated control of resection in human cells operates by mechanisms similar to those recently established in yeast.