Overexpression of a kinase-inactive ATR protein causes sensitivity to DNA-damaging agents and defects in cell cycle checkpoints

Abstract

6 Corresponding author ATR, a phosphatidylinositol kinase-related protein homologous to ataxia telangiectasia mutated (ATM), is important for the survival of human cells following many forms of DNA damage. Expression of a kinaseinactive allele of ATR (ATRkd) in human fibroblasts causes increased sensitivity to ionizing radiation (IR), cis-platinum and methyl methanesulfonate, but only slight UV radiation sensitivity. ATRkd overexpression abrogates the G 2 /M arrest after exposure to IR, and overexpression of wild-type ATR complements the radioresistant DNA synthesis phenotype of cells lacking ATM, suggesting a potential functional overlap between these proteins. ATRkd overexpression also causes increased sensitivity to hydroxyurea that is associated with microtubule-mediated nuclear abnormalities. These observations are consistent with uncoupling of certain mitotic events from the completion of S-phase. Thus, ATR is an important component of multiple DNA damage response pathways and may be involved in the DNA replication (S/M) checkpoint.

Chk1 complements the G2/M checkpoint defect and radiosensitivity of ataxia-telangiectasia cells

“…While S. pombe rad3 is related to ATM, its closest human homologue is ATR/FRPI Cimprich et al, 1996). Overexpression of a`kinase dead' mutant of ATR increases sensitivity to ionizing radiation and abrogates radiation-induced G2 arrest (Cliby et al, 1998). In addition complementation of the S phase defect in A-T ®broblasts occurs after overexpression of wild type ATR.…”

Differential response of normal and malignant urothelial cells to CHK1 and ATM inhibitors

“…Since ATM and its downstream protein Chk2 are considered as regulators which participate in a pathway in parallel to ATR (Cliby et al, 1998) and shares some overlapping function such as Cdc25A phosphorylation Zhao et al, 2002), it is worthwhile to examine the relationship between ATM and ATR pathways particularly in DNA replication stress -induced checkpoint system. A hypothesis was proposed that ATM replaces ATR-CHK1 and acts as the major regulator in cell cycle progression in normal urothelial cells following replication defects.…”

ATM: A mediator of multiple responses to genotoxic stress

“…The mammalian family member most closely related to ATM is the ATR/FRP1 protein; like its homologs in yeast (Rad3 of S. pombe and Mec1 of S. cerevisiae), it mediates cellular responses to unreplicated or damaged DNA (Cliby et al, 1998;Wright et al, 1998).…”