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Cell. 1995 Aug 25;82(4):675-84.

Mice lacking p21CIP1/WAF1 undergo normal development, but are defective in G1 checkpoint control.

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Howard Hughes Medical Institute, Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.


p21CIP1/WAF1 is a CDK inhibitor regulated by the tumor suppressor p53 and is hypothesized to mediate G1 arrest. p53 has been suggested to derive anti-oncogenic properties from this relationship. To test these notions, we created mice lacking p21CIP1/WAF1. They develop normally and (unlike p53-/- mice) have not developed spontaneous malignancies during 7 months of observation. Nonetheless, p21-/- embryonic fibroblasts are significantly deficient in their ability to arrest in G1 in response to DNA damage and nucleotide pool perturbation. p21-/- cells also exhibit a significant growth alteration in vitro, achieving a saturation density as high as that observed in p53-/- cells. In contrast, other aspects of p53 function, such as thymocytic apoptosis and the mitotic spindle checkpoint, appear normal. These results establish the role of p21CIP1/WAF1 in the G1 checkpoint, but suggest that the anti-apoptotic and the anti-oncogenic effects of p53 are more complex.

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