The permissive effect of p21(Waf1/Cip1) on DNA synthesis is dependent on cell type: effect is absent in p53-inactive cells.
The cyclin-dependent kinase inhibitors (CKI) interact with cyclin-cdk complexes to arrest mitogen-stimulated transit through the cell cycle, but we and others have recently shown that these molecules can exert permissive effects on cell cycle transit as well. The p53 protein induces transcription of the p21(Waf1/Cip1) gene, but whether p53 has any effect on the stimulatory versus inhibitory state of p21(Waf1/Cip1) toward cell growth is not known. The focus of the current study was to examine the effect of p21(Waf1/Cip1) inhibition on growth in cells which possess an inactive p53 protein. We found that there was significant and specific inhibition of p21(Waf1/Cip1) protein transcription in human squamous carcinoma A431 cells after transfection of an antisense p21(Waf1/Cip1) oligodeoxynucleotide, yet there was no significant growth inhibition in these cells after stimulation with 10% serum or with PDGF-BB, in contrast to what was observed in vascular smooth muscle (VSM) cells. Furthermore, there was no attenuation of either cyclinD/cdk4 association or of Rb hyperphosphorylation after antisense p21(Waf1/Cip1) oligodeoxynucleotide transfection, suggesting that an alternate pathway exists to allow association and phosphorylation of these cell cycle components in the absence (or with lower levels) of p21(Waf1/Cip1). Thus, the permissive effect of p21(Waf1/Cip1) toward growth is dependent on cell type, and active p53 is likely required for this effect.
Weiss
R H
RH
Division of Nephrology, Department of Internal Medicine, University of California, Davis, CA 95616, USA. rhweiss@ucdavis.edu
Randour
C J
CJ
D000818:Animals; D000077214:Becaplermin; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D002453:Cell Cycle / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line / Q000378:metabolism; D003470:Culture Media / Q000494:pharmacology; D056741:Cyclin D; D051358:Cyclin-Dependent Kinase 4; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism / Q000502:physiology*; D004261:DNA Replication; D005312:Fetal Blood / Q000502:physiology; D005786:Gene Expression Regulation; D016158:Genes, p53; D006801:Humans; D008954:Models, Biological; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics; D009928:Organ Specificity; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D011518:Proto-Oncogene Proteins; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
C493956:CDKN1A protein, human; C493958:Cdkn1a protein, rat; D003470:Culture Media; D056741:Cyclin D; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D020319:Oligodeoxyribonucleotides, Antisense; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D000077214:Becaplermin; C495900:CDK4 protein, human; C495903:Cdk4 protein, rat; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases