Transforming growth factor-beta regulation of retinoblastoma gene product and E2F transcription factor during cell cycle progression in mouse fibroblasts.
The mechanism by which transforming growth factor beta (TGF beta) exerts growth stimulatory effects was examined in C3H/10T1/2 mouse fibroblasts by study of cell cycle regulation of the retinoblastoma gene product (p110Rb) and transcriptional regulation of the p110Rb-associated transcription factor, E2F. Northern blotting analysis shows that TGF beta and/or epidermal growth factor (EGF) stimulate by three to sixfold the level of Rb mRNA which is also reflected by the increased levels of p110Rb. p110Rb becomes phosphorylated in mid-G1 and further phosphorylated at the G1/S transition. Hyperphosphorylation of p110Rb by TGF beta can be observed when cells are in S phase. TGF beta stimulates by three to fourfold the activity of cdk2 kinase consistent with the observed phosphorylation of p110Rb and also with the possibility that the kinase is involved in phosphorylating p110Rb close to the G1/S transition. Thus, TGF beta as a growth stimulator induces, as does EGF, the phosphorylation of p110Rb during cell cycle progression. Transient transfection of E2F promoter constructs was used to analyze the effect of TGF beta on the modulation of E2F-mediated transcription. The data revealed that TGF beta can stimulate wild-type adenoviral E2 promoter activity by 12-fold. Taken together, TGF beta-induced phosphorylation of p110Rb in mouse fibroblasts appears to exert a positive regulatory function upon genes that have a pivotal role in the G1/S transition of the cell cycle.
Department of Biochemistry, Roswell Park Cancer Institute, Buffalo, New York 14263.
T A
TA
Kim
M J
MJ
Ravitz
C E
CE
Wenner
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D042846:CDC2-CDC28 Kinases; D002352:Carrier Proteins; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D002460:Cell Line; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D016161:Genes, Retinoblastoma; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011494:Protein Kinases / Q000032:analysis / Q000235:genetics / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D016160:Retinoblastoma Protein / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
C533431:Arid4a protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases