Accumulation of high levels of the p53 and p130 growth-suppressing proteins in cell lines stably over-expressing cyclin-dependent kinase 6 (cdk6).
Cyclin-dependent kinase 6(cdk6) is present in randomly proliferating cultures of 3T3 cells but has little detectable enzymatic activity. Significant activity is detected only during a short period in early G1 phase. To examine the possible functions of cdk6 in 3T3 cells, lines stably over-expressing cdk6 were constructed and compared to normal 3T3 cells or cell lines with reduced cdk6 levels due to expression of a dominant-negative form of the protein. Over-expression of cdk6 in cells, which led to high levels of activity even in proliferating cultures, had dramatic effects. Cell lines stably over-expressing wild-type cdk6 had a markedly reduced growth rate compared to parental 3T3 cells or lines expressing a dominant-negative form of cdk6. They also over-produced the p53 and p130 proteins and had increased sensitivity to UV-irradiation. Irradiation resulted in accumulation of the Bax protein and rapid cell death. Levels of p53 and p130 proteins were down-regulated and the growth rate of the cells was increased by introduction of the dominant-negative form of cdk6 into cells over-expressing cdk6, indicating that cdk6 is involved in the overproduction of p53 and p130. The results suggest that cdk6, through regulation of growth-suppressing molecules, may play a role in halting cellular growth when proliferation is inappropriate.
Nagasawa
M
M
Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, Colorado, CO 80206, USA.
Gelfand
E W
EW
Lucas
J J
JJ
D016475:3T3 Cells / Q000528:radiation effects; D000818:Animals; D002455:Cell Division / Q000235:genetics; D002460:Cell Line / Q000528:radiation effects; D016895:Culture Media, Serum-Free; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D019253:Proto-Oncogene Proteins c-bcl-2; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
C494827:Bax protein, mouse; D016895:Culture Media, Serum-Free; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D017346:Protein Serine-Threonine Kinases; C495912:Cdk6 protein, mouse; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases