Enhanced activity of cyclin A-associated kinase in immortalized human fibroblasts.
Deregulation of cell cycle regulatory mechanisms leads to disruption of normal control of cell growth and may be associated with neoplastic transformation. To determine whether immortalized human cells have alterations in their cell cycle regulatory mechanisms, we analyzed cell cycle regulatory proteins in 2 immortalized human fibroblast cell lines, KMST-6 and OUMS-24/P6X, established by repeated irradiation with (60)Co gamma rays alone or mutant p53 gene transfection plus X-ray irradiation, respectively. Both the immortalized cell lines had markedly enhanced activity of cyclin A-associated kinase as compared with their normal counterparts. The high activity of cyclin A-associated kinase was well correlated with the increased expression of cyclin A mRNA and its protein. In addition, the immortalized cell lines showed significantly reduced amounts of p21(Cip1/Waf1/Sdi1), a potent inhibitor of cyclin dependent kinases. Furthermore, among the pRb family of proteins, p107 and p130, were hyperphosphorylated in both the immortalized cell lines, suggesting possible participation in upregulation of cyclin A associated kinase activity. These changes represent some important characteristics of immortalized cells.
Department of Cell Biology, Institute of Molecular and Cellular Biology, Okayama University Medical School, Okayama, Japan.
R
R
Ohashi
M
M
Miyazaki
K
K
Fushimi
T
T
Tsuji
Y
Y
Inoue
N
N
Shimizu
M
M
Namba
D001798:Blood Proteins / Q000378:metabolism; D002453:Cell Cycle; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D019927:Cyclin E; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011506:Proteins; D012333:RNA, Messenger / Q000378:metabolism; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130
D001798:Blood Proteins; D019925:Cyclin A; D019927:Cyclin E; D009687:Nuclear Proteins; D011506:Proteins; C493844:RBL1 protein, human; C493837:RBL2 protein, human; D012333:RNA, Messenger; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D011494:Protein Kinases; C102333:histone H1 kinase; D018844:Cyclin-Dependent Kinases