ATM is activated by mitotic stress and suppresses centrosome amplification in primary but not in tumor cells.

Centrosome amplification has been proposed to contribute to the development of aneuploidy and genome instability. Here, we show that Ataxia-Telangiectasia Mutated (ATM) is localized to the centrosome and co-purified with gamma-tubulin. The importance of ATM in centrosome duplication is demonstrated in Atm-deficient primary mouse embryonic fibroblasts that display centrosome amplification. Interestingly, centrosome amplification was not observed in tumor cell lines derived from Atm and p21 double deficient mouse. Our results also indicate that both p53 and p21 operate in the same pathway as ATM in regulating centrosome biogenesis. Finally, a potential role of ATM in spindle checkpoint regulation is demonstrated by which ATM protein is activated by mitotic stress. These results suggest a role of ATM in spindle checkpoint regulation and indicate that ATM suppresses genome instability and cellular transformation by regulating centrosome biogenesis. 2006 Wiley-Liss, Inc.