Failure to induce inhibition of cyclin A and up-regulation of p21 expression in phorbol ester-resistant U937 cells by phorbol ester.
Differentiation resistant U937 cells were derived from parental U937 cells by selecting for continuously growing U937 cells in cell cultures continuously exposed to phorbol 12 myristate 13-acetate (PMA). Unlike in other known PMA resistant U937, the basal expression of protein kinase C (PKC) isozymes in these PMA resistant cells (R-U937) was significantly decreased. Subsequent analyses revealed differences between the wild type U937 and the R-U937 cells with respect to G1 phase arrest, which seemed to occur in U937 because of low levels of cdk2 kinase activity. This abolished cdk2 kinase activity is mainly due to inhibition of cdk2 phosphorylation, cyclin A down-regulation and cyclin dependent kinase inhibitor p21 up-regulation. Our data suggest that events down-stream of PKC activation may mediate cell cycle control. Thus, the R-U937 cells could be useful for further PKC mediated cell cycle control studies.
Department of Immunology, Keimyung University, School of Medicine, 194 Dong-San Dong, Jung-Gu, Taegu, South Korea.
T K
TK
Kwon
S
S
Baek
Y J
YJ
Lee
Y
Y
Lee
J
J
Kim
J H
JH
Kim
S
S
Suh
M
M
Suh
W
W
Baek
O
O
Bang
J
J
Park
D015153:Blotting, Western; D002452:Cell Count; D019925:Cyclin A / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000378:metabolism*; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000378:metabolism*; D005434:Flow Cytometry; D016193:G1 Phase; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007938:Leukemia / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism / Q000494:pharmacology*; D020298:U937 Cells / Q000378:metabolism; D015854:Up-Regulation
C493956:CDKN1A protein, human; D019925:Cyclin A; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D011493:Protein Kinase C; D018844:Cyclin-Dependent Kinases; D013755:Tetradecanoylphorbol Acetate