DNA-dependent protein kinase inhibitor (OK-1035) suppresses p21 expression in HCT116 cells containing wild-type p53 induced by adriamycin.
The tumor growth suppressor p21 has been shown to be induced by wild-type p53 (wt-p53) and to be a potent inhibitor of cyclin-dependent kinases and PCNA/DNA polymerase delta. Although wt-p53 is reported to be phosphorylated by several protein kinases, the function and significance of the phosphorylation of wt-p53 are not yet fully understood. Using OK-1035, a selective inhibitor of DNA-dependent protein kinase (DNA-PK), we demonstrated the importance of the phosphorylation of wt-p53 by DNA-PK in the DNA damage-mediated expression of the p21 gene. Treatment of HCT116, a human colon carcinoma cell line, with adriamycin induced the expression of wt-p53 and p21. By addition of OK-1035 to this culture, the induction of p21 protein was significantly decreased in a dose-dependent manner, whereas wt-p53 induction was not affected. Northern blot analysis revealed that suppression of p21 protein expression by OK-1035 resulted from reduction in the level of p21 mRNA. OK-1035 did not directly affect the binding ability of wt-p53 to its consensus DNA sequence. Our observations support the idea that wt-p53 induces the transcriptional activation of the p21 gene only after it is phosphorylated by DNA-PK.
Take
Y
Y
Banyu Research Institute, Tsukuba, Japan.
Kumano
M
M
Teraoka
H
H
Nishimura
S
S
Okuyama
A
A
D000595:Amino Acid Sequence; D001483:Base Sequence; D016384:Consensus Sequence; D004247:DNA / Q000187:drug effects; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D004317:Doxorubicin / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D006835:Hydrazones / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D015689:Oncogene Protein p21(ras) / Q000235:genetics*; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011728:Pyridones / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
C095985:3-cyano-5-(4-pyridyl)-6-hydrazonomethyl-2-pyridone; D004268:DNA-Binding Proteins; D006835:Hydrazones; D009687:Nuclear Proteins; D011728:Pyridones; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D015689:Oncogene Protein p21(ras)