Adenovirus E1A: Implications of a Post-Translational Modification for Nuclear Localization and Stimulation of Transcription

Abstract

The E1A gene is one of the first viral genes to be expressed following adenovirus infection of permissive cells. Several functions have been ascribed to the E1A gene product which include the trans activation of other viral genes (1–3) and certain cellular genes (4,5), the immortalization and partial transformation of cells (6), and, when acting in concert with other oncogenes, the complete transformation of cells (7). Two mRNAs which are encoded by the E1A gene are synthesized during the early phase of a productive infection. These mRNAs, 12S and 13S, are derived from the same primary transcript by in-frame alternative splicing and encode proteins which contain 243 and 289 amino acid residues, respectively (8). The proteins have identical termini and differ solely by the number of internal amino acid residues. Analysis of the E1A proteins by SDS polyaerylamide gel electrophoresis reveals four prominant species (9–11). It has been suggested that post-translational modifications of each of the primary proteins lead to these molecular weight variants (10). The biological significance of these modifications is not known.