A potent transrepression domain in the retinoblastoma protein induces a cell cycle arrest when bound to E2F sites.
An intact T/E1A-binding domain (the pocket) is necessary, but not sufficient, for the retinoblastoma protein (RB) to bind to DNA-protein complexes containing E2F and for RB to induce a G1/S block. Indirect evidence suggests that the binding of RB to E2F may, in addition to inhibiting E2F transactivation function, generate a complex capable of functioning as a transrepressor. Here we show that a chimera in which the E2F1 transactivation domain was replaced with the RB pocket could, in a DNA-binding and pocket-dependent manner, mimic the ability of RB to repress transcription and induce a cell cycle arrest. In contrast, a transdominant negative E2F1 mutant that is capable of blocking E2F-dependent transactivation did not. Fusion of the RB pocket to a heterologous DNA-binding domain unrelated to E2F likewise generated a transrepressor protein when scored against a suitable reporter. These results suggest that growth suppression by RB is due, at least in part, to transrepression mediated by the pocket domain bound to certain promoters via E2F.
Dana-Farber Cancer Institute, Boston, MA, USA.
W R
WR
Sellers
J W
JW
Rodgers
W G
WG
Kaelin
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D004247:DNA