Phosphorylation of hRad17 by ATR is Required for Cell Cycle Checkpoint Activation
Abstract
ATR is protein kinase required for both DNA damage-induced cell cycle checkpoint responses and the DNA replication checkpoint, which prevents mitosis before completion of DNA synthesis. Although ATM and ATR share many substrates, the different phenotypes observed in ATM- and ATR- deficient mice indicate these kinases are not functionally redundant. We have shown that ATR but not ATM phosphorylated human Rad17 on serines 635 and 645 in vitro and in vivo. In undamaged cells, these same sites are phosphorylated in late G1, S, and G2, but not in early G1; however, treatment with genotoxic agents induces phosphorylation of hRad17 in early G1. Additionally, Radl7 is phosphorylated in actively replicating but not quiescent cells in an ATM-independent manner. Expression of a phosphorylation mutant hRad17, with both serines changed to alanine, abolishes IR-induced activation of the G1/S checkpoint and results in cellular sensitivity to IR in the breast cancer cell line, MCF- 7. These results suggest ATR and hRad17 are required for an ATM-independent DNA damage response pathway. Additionally, these results demonstrate the kinase activity of ATR on hRad17 is activated in response to DNA damage and during normal replication and indicates the hRad17 may play a role during normal DNA synthesis.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2003
- Accession Number
- ADA416664
Entities
People
- Sean M. Post
- Wen-hwa Lee
Organizations
- University of Texas Health Science Center at San Antonio