Evidence that a second tumor antigen coded by adenovirus early gene region E1a is required for efficient cell transformation.

Abstract

The expression of the adenovirus (Ad) early coding region la (Ela) is required for virus-induced cell transformation and for the activation of other viral early genes and some cellular genes. Two overlapping early mRNAs of 13S and 12S that are transcribed from this region code for a 289-amino acid protein and a 243-amino acid protein, respectively. Earli Oncogenic transformation by adenoviruses is a function of both the Ela and Elb (mp 4.5-11.3) regions as determined by the analysis of virus-transformed cells (5, 6), DNA transfection (7-9), and the use of viral mutants (10)(11)(12)(13)(14). DNA transfection studies have shown that Ela can partially transform baby rat kidney (BRK) cells (15). These Ela-transformed cells are "immortalized," whereas their morphology and growth pattern resemble those of untransformed cells. In addition to the immortalization function, Ela also appears to have a transforming function, since immortalized rat embryo cells cannot be transformed by DNA constructs capable of expressing Elb without Ela (9).The Ela gene also has been shown to facilitate the transformation of BRK cells by cellular oncogenes. The human cellular oncogene Ha-ras isolated from a bladder carcinoma is unable to transform BRK cells. However, Ha-ras can be complemented by the Ad2 Ela gene to produce full transformation and tumorigenecity (16).The Ela gene encodes three overlapping mRNAs that have identical 5' and 3' termini (Fig. 1). They differ in the size of the intron removed during splicing. Each uses a common 3'-splice site junction (acceptor) but differs in the location of the 5'-splice site junction (donor). The 13S and 12S mRNAs are expressed during the early stage of the productive cycle (21, 22) and in transformed cells (23,24). The 9S mRNA does not accumulate to significant levels except during the late stage of the productive cycle (25) and is not essential for viral growth during productive infection (26). The 9S mRNA has not been detected in any of the Ad-transformed cells examined (24,26). These studies indicate that the proteins encoded by the 13S mRNA and/or the 12S mRNA play an essential role in cell transformation. Viral mutants (27, 28) and plasmid constructs (29) have demonstrated the requirement of the 289-amino acid tumor antigen coded by the 13S mRNA for transformation.To investigate the role of the Ela 243-amino acid tumor antigen coded by the 12S mRNA in cell transformation and the productive cycle, we constructed an Ad2 Ela deletion mutant that specifically and precisely lacks the Ela 13S mRNA intervening sequence (IVS). It recently has been shown that the splicing of Ela mRNAs is nonsequentialthat each mRNA is produced from an unspliced nuclear precursor and not from an intermediate (i.e., 13S mRNA does not mature into 12S mRNA or 9S mRNA) (30). Therefore, our deletion mutant, which lacks the 13S IVS, cannot produce functional 12S mRNA. Our results demonstrate that the 243-amino acid tumor antigen is required for full transformation of rat embryo cells. MATERIALS AND METHODSConstr...

Adenoviral-mediated gene transfer to rabbit synovium in vivo.

“…Replication defective adenoviral vectors are deleted of sequences spanning EIA, EIB, and a portion of the E3 region, impairing the ability of this virus to replicate or transform nonpermissive cells ( 13). In the vector AdCMVlacZ, the early enhancer/promoter of the cytomegalovirus (CMV)' was used to drive transcription of lacZ with an SV40 polyadenylation sequence cloned downstream from this reporter.…”

Transplantation of transduced chondrocytes protects articular cartilage from interleukin 1-induced extracellular matrix degradation.

“…In (24). Transgene transcription was driven by the early enhancer/promoter of the cytomegalovirus (CMV) in the vector Ad.-CMV lacZ and the Rous sarcoma virus (RSV) long-terminal repeat in the vectors Ad.RSV ntlacZ and Ad.RSV hIL-ira.…”

Different functional domains of the adenovirus E1A gene are involved in regulation of host cell cycle products.

“…1). The presence of conserved domain 3 in the ElA products appears to correlate strongly with the ability of the ElA gene products to trans activate the other virus genes efficiently, while various transformation-related activities of the ElA region appear to be independent of this domain (8,15,21,23,26,42,43,50,63,73).…”