The role of adenovirus early region 1A in the regulation of early regions 2A and 1B expression.

The role of the adenovirus early region 1A (E1A) in the regulation of expression of early regions 2A (E2A) and 1B (E1B) has been investigated by microinjection of cloned segments of viral DNA into cultured cells. Plasmids carrying adenoviral sequences that code for the DNA binding protein (DBP) associated with either the early or the late E2A promoter (at map coordinates 75 and 72, respectively), or both promoters, were injected into cell nuclei in the presence or absence of a plasmid DNA containing early region 1A. The injected cells were scored for the expression of the DNA binding protein by indirect immunofluorescence using specific antisera. These studies suggest that the product(s) encoded by early region 1A differentially control the expression of the DNA binding protein. DBP produced from the early promoter is stimulated by addition of the E1A region. By contrast E1A gene product(s) inhibit the synthesis of the DBP species transcribed from the late promoter. It has been shown previously by a variety of studies that E1A regulates E1B expression. However, experiments in which E1B DNA was microinjected together with E1A and E2A suggest that the DNA binding protein may have a stimulatory effect on the synthesis of E1B products.