Mutational analysis of the adenovirus E1a gene: the role of transcriptional regulation in transformation.

Abstract

To determine whether the transcription regulatory activities of the adenoviral E1a gene play a role in its ability to transform primary cells we have constructed an extensive series of mutations within the E1a gene. The mutants have been characterized for their ability to transactivate the adenoviral early promoters, repress the transcriptional stimulation of the polyoma virus enhancer, establish primary baby rat kidney cells in culture and cooperate with the activated Ha‐ras oncogene in morphologically transforming these cells. The mutant phenotypes reveal that: (i) the two transcription regulatory activities of E1a are separable since essential protein domains map within different regions of the protein; (ii) transactivation is unlikely to contribute significantly to E1a‐mediated transformation since several isolated mutants lost the ability to transactivate but were nevertheless efficient at transformation; and (iii) both establishment and oncogene cooperation are linked to enhancer repression suggesting that E1a transforms cells by the repression of a cellular enhancer.

Trans-activation of the adenovirus E2 promoter by human papillomavirus type 16 E7 is mediated by retinoblastoma-dependent and -independent pathways

“…Mutational analysis of the E7 gene has demonstrated partial resolution of its trans-activating and transforming activities, but no mutations abolish one of these activities without impairing the other (Barbosa et al, 1990; Short communication Edmonds & Vousden, 1989;Storey et al, 1990;Watanabe et al, 1990). This is in contrast to the situation with the adenovirus Ela gene (Moran et al, 1986;Schneider et al, 1987), which otherwise shares many similarities with E7. It is therefore likely that the pathway by which E7 induces transformation is similar or identical to the pathway by which it trans-activates and that interaction of E7 with the same set of cellular proteins endows the gene with both activities.…”

Identification of factors that interact with the E1A-inducible adenovirus E3 promoter.

“…Both products display regulatory activity; the product of 289 amino acids can trans-activate and repress gene transcription (Borrelli et al 1984;Velcich and Ziff 1985), whereas the protein of 243 amino acids, although it represses very efficiently (Borrelli et al 1984;Velcich and Ziff 1985), is generally found to be deficient in trans-activation (Carlock and Jones 1981;Montell et al 1982;Svensson and Akusjarvi 1984;Winberg and Shenk 1984;Lillie et al 1986;Moran et al 1986;Wu et al 1986a). Furthermore, extensive mutational analysis of the E1A gene has identified domains that are required for repression but not for trans-activation (Lillie et al 1986;Moran et al 1986;Schneider et al 1987). Consequently, these two regulatory activities of E1A have been shown to be separable, but their mode of action remains unclear.…”

Mapping of adenovirus 5 E1A domains responsible for suppression of neu-mediated transformation via transcriptional repression of neu

“…The E1A CR2 domain is known to bind with the RB family of proteins, leading to immortalization of the primary culture cells and in cooperation with ras or E1B oncogenes, E1A can lead to transformation (Whyte et al, 1989;Corbeil and Branton, 1994). Deletion of the CR2 domain or even a site mutation to knock out the RB-binding site on E1A is su cient to abolish the immortalization function of E1A (Lillie et al, 1986;Moran et al, 1986;Zerler et al, , 1987Schneider et al, 1987;Kuppuswamy and Chinnadurai, 1987;Smith and Zi , 1988;Jelsma et al, 1989;Whyte et al, 1989). Thus, the deletion of the CR2 and CR3 domains in the mini-E1A would abolish the potential risk of immortalization and consequent transformation caused by wild type E1A.…”