E4F Transcription Factor 1 (E4F1)

The zinc finger protein encoded by this gene is one of several cellular transcription factors whose DNA-binding activities are regulated through the action of adenovirus E1A. A 50-kDa amino-terminal product is generated from the full-length protein through proteolytic cleavage. The protein is differentially regulated by E1A-induced phosphorylation. The full-length gene product represses transcription from the E4 promoter in the absence of E1A, while the 50-kDa form acts as a transcriptional activator in its presence.

Specific inactivation of RASSF1A by short interfering RNA disrupted the binding of RASSF1A to E4F1 in immunoprecipitation assays. In addition, there was enhanced G1 cell cycle arrest and S-phase inhibition by E4F1 in the presence of RASSF1A.