E2F-1-mediated transactivation is inhibited by complex formation with the retinoblastoma susceptibility gene product.

Flemington EK; Speck SH; Kaelin WG Jr

Division of Tumor Virology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115.

Proc Natl Acad Sci U S A 90: 6914-8 (1993)

Abstract
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.

Mesh Headings

Base Sequence

DNA Mutational Analysis

Gene Expression Regulation*

Human

In Vitro

Macromolecular Systems

Molecular Sequence Data

Oligodeoxyribonucleotides

Retinoblastoma Protein*

Sequence Deletion

Support, Non-U.S. Gov't

Support, U.S. Gov't, P.H.S.

Trans-Activation (Genetics)*

Transcription Factors*

Transcription, Genetic*

Tumor Cells, Cultured

Unique Identifier: 93348182

Chemical Identifiers (Names)

(transcription factor E2F)

(Macromolecular Systems)

(Oligodeoxyribonucleotides)

(Retinoblastoma Protein)

(Transcription Factors)