Regulation of cellular genes in a chromosomal context by the retinoblastoma tumor suppressor protein.
The retinoblastoma tumor suppressor gene product (pRb) is involved in controlling cell cycle progression from G1 into S. pRb functions, in part, by regulating the activities of several transcription factors, making pRb involved in the transcriptional control of cellular genes. Transient-transfection assays have implicated pRb in the transcription of several genes, including c-fos, the interleukin-6 gene, c-myc, cdc-2, c-neu, and the transforming growth factor beta2 gene. However, these assays place the promoter in an artificial context and exclude the effects of far 5' upstream regions and chromosomal architecture on gene transcription. In these experiments, we have studied the role of pRb in the control of cell cycle-related genes within a chromosomal context and within the context of the G1 phase of the cell cycle. We have used adenovirus vectors to overexpress pRb in human osteosarcoma cells and breast cells synchronized in early G1. By RNase protection assays, we have assayed the effects of this virus-produced pRb on gene expression in these cells. These results indicate that pRb is involved in the transcriptional downregulation of the E2F-1, E2F-2, dihydrofolate reductase, thymidine kinase, c-myc, proliferating-cell nuclear antigen, p107, and p21/Cip1 genes. However, it has no effect on the transcription of the E2F-3, E2F-4, E2F-5, DP-1, DP-2, or p16/Ink4 genes. The results are consistent with the notion that pRb controls the transcription of genes involved in S-phase promotion. They also suggest that pRb negatively regulates the transcription of two of the transcription factors whose activity it also represses, E2F-1 and E2F-2, and that it plays a role in downregulating the immediate-early gene response to serum stimulation.
Robert H. Lurie Cancer Center and Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois 60611-3088, USA.
A M
AM
Buchmann
S
S
Swaminathan
B
B
Thimmapaya
D000260:Adenoviruses, Human; D001665:Binding Sites; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002455:Cell Division; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D004268:DNA-Binding Proteins; D015536:Down-Regulation; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050703:E2F2 Transcription Factor; D050699:E2F3 Transcription Factor; D050704:E2F4 Transcription Factor; D050700:E2F5 Transcription Factor; D016193:G1 Phase; D005822:Genetic Vectors; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics; D018809:Proliferating Cell Nuclear Antigen / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D056465:Retinoblastoma-Binding Protein 1; D050720:Retinoblastoma-Like Protein p107; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
C493956:CDKN1A protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D050703:E2F2 Transcription Factor; C493761:E2F2 protein, human; D050699:E2F3 Transcription Factor; D050704:E2F4 Transcription Factor; C493762:E2F4 protein, human; D050700:E2F5 Transcription Factor; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen; D016271:Proto-Oncogene Proteins c-myc; C493844:RBL1 protein, human; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050720:Retinoblastoma-Like Protein p107; C493735:TFDP1 protein, human; D050680:Transcription Factor DP1; D014157:Transcription Factors; D013762:Tetrahydrofolate Dehydrogenase; D013937:Thymidine Kinase