TRANSCRIPTIONAL REPRESSION BY HUMAN ADENOVIRUS E1A N-TERMINUS CONSERVED DOMAIN-1 POLYPEPTIDES IN-VIVO AND IN-VITRO IN THE ABSENCE OF PROTEIN-SYNTHESIS

The human adenovirus E1A 243R protein (243 residues) transcriptionally represses a set of cellular genes that regulate cellular growth and d ifferentiation. We describe two lines of evidence that E1A repression does not require cellular protein synthesis but instead involves direc t interaction with a cellular protein(s). First, E1A 243R protein repr esses an E1A repressible promotor in the presence of inhibitors of pro tein synthesis, as shown by cell microinjection-in situ hybridization. Second, E1A 243R protein strongly represses transcription in vitro fr om promoters of the E1A-repressible genes, human collagenase, and rat insulin type II. Repression in vitro is promoter-specific, and an E1A polypeptide containing only the N-terminal 80 residues is sufficient f or strong repression both in vivo and in vitro. By use of a series of E1A 1-80 deletion proteins, the E1A repression function was found to r equire two E1A sequence elements, one within the nonconserved E1A N te rminus, and the second within a portion of conserved region 1 (40-80). These domains have been reported to possess binding sites for several cellular transcription regulators, including p300, Dr1, YY1, and the TBP subunit of TFIID. The in vitro transcription-repression system des cribed here provides a powerful tool for the fur ther analysis of mole cular mechanism and the possible role of these cellular factors.