Identification of the region required for the antiapoptotic function of the cyclin kinase inhibitor, p21.
The CDK inhibitor, p21, exhibits an antiapoptotic or proapoptotic effect, in addition to its anti-proliferative effect, depending on the conditions. To define the apoptosis-regulatory function of p21, we constructed cells that stably express C-terminal deletion mutants of p21 (full length 164aa), 1-157, 1-147 or 1-128, and evaluated the apoptotic response of these cells. The AnnexinV positive cell fraction after gamma-irradiation did not increase in cells expressing 1-157. Consistently, an increase of caspase3 activity or the active form of caspase3 was not observed in cells expressing 1-157, but was prominent in cells expressing 1-128 and 1-147. Further, the activity of caspase9 was suppressed in gamma-irradiated cells expressing 1-157. The antiapoptotic effect of 1-157 was weaker in Fas-induced apoptosis. Our data indicate that the 1-157 region of p21 inhibits apoptosis caused by gamma-irradiation by reducing the activity of caspase9 and caspase3, and the 148-157 region is critical for its inhibiting activity.
Department of Biochemistry, Showa University, School of Medicine 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8666, Japan.
Kentarou
K
Nakamura
Daisuke
D
Arai
Kunihiko
K
Fukuchi
D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D005720:Gamma Rays; D006801:Humans; D009154:Mutation; D014162:Transfection
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D018844:Cyclin-Dependent Kinases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases