E2F-1-mediated transactivation is inhibited by complex formation with the retinoblastoma susceptibility gene product.
Previous studies have shown that the carboxyl-terminal region of E2F-1 (residues 368-437) can support transcriptional activation when linked to the DNA-binding domain of the yeast transcription factor GAL4. This region also contains an 18-residue retinoblastoma (RB)-binding sequence, raising the possibility that RB binding might inhibit the ability of E2F-1 to form protein-protein contacts required for activation. Here we report a further analysis of the E2F-1 activation domain. In addition, we show that overexpression of RB, but not the RB mutant, RBd22, can inhibit GAL4/E2F-1 activity in vivo. Moreover, expression of the simian virus 40 large tumor antigen (T antigen), but not the RB-binding defective T antigen point mutant, K1, can overcome this repression. Three different GAL4/E2F-1 mutants that activate transcription, but fail to bind to RB, are not significantly affected by overexpression of RB. These findings support a model wherein RB suppresses E2F-1-mediated transcriptional activation through direct physical association.
Flemington
E K
EK
Division of Tumor Virology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115.
Speck
S H
SH
Kaelin
W G
WG
D001483:Base Sequence; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005786:Gene Expression Regulation; D006801:Humans; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D016160:Retinoblastoma Protein / Q000378:metabolism*; D056465:Retinoblastoma-Binding Protein 1; D017384:Sequence Deletion; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors