Adenovirus E1A 12S protein induces DNA synthesis and proliferation in primary epithelial cells in both the presence and absence of serum

Abstract

Infection of primary baby rat kidney (BRK) cells with an adenovirus that carries an ElA 12S cDNA in place of the normal ElA region (adenovirus 5 [Ad5] 12S) resulted in the induction of cellular DNA synthesis and proliferation of the epithelial cells in the population, even in the absence of serum. Increased cellular DNA synthesis was first detectable by 12 h after infection and was maintained at a 10-to 20-fold higher level than in mock-infected cells. By 5 days after infection there was a 10-fold-greater number of 12S virus-infected BRK cells. These infected BRK cells retained many of their normal epithelial cell characteristics and were not transformed. The expression of the ElA 12S protein(s) occurred early after infection. There was no induction of adenoviral gene expression or viral DNA replication in these cells. The early effects of a fully transforming gene product(s) were also examined. The Ad5-simian virus 40 hybrid virus, Ad5.SVR4, in which the early region of simian virus 40 has replaced the El region of AdS, was used to infect BRK cells. The kinetics of expression of the T antigens were similar to those of the 12S polypeptides. Infection with Ad5.SV4 also resulted in the induction of cellular DNA synthesis and cell proliferation at levels similar to those observed with the 12S virus. However, infection with Ad5.SVR4 resulted in cells that had lost some of their epithelial cell characteristics and were fully transformed. Thus, although the early cellular events induced by the two genes were similar, they did not yield the same final ceUlular phenotype.on July 6, 2020 by guest

Regulation of adenovirus and cellular gene expression and of cellular transformation by the E1B-encoded 175-amino-acid protein

“…This labeled RNA is then hybridized to excess DNA bound to nitrocellulose filters. The following DNA clones were used as probes on filters: ElA 5', 0 to 1,338 nucleotides; ElA 3', 1,338 to 1,538 nucleotides; E1B 5', 2,058 to 2,486 nucleotides; E1B 3', 3,328 to 3,786 nucleotides; E2A, 22,179 to 22,435 nucleotides; E4, 32,264 to 35,937 nucleotides; chicken P-actin (16); and mouse IGN heavy chain gene, -2,000 to + 1,700 nucleotides relative to the transcriptional start site (49).…”

“…By using a variety of genetic approaches it has been demonstrated that the 289R protein is necessary for modulating the rate of transcription from several viral early promoters (9, 13, 31, 45, 50) and some cellular genes (21,54), probably through its modification of some preexisting or induced cellular transcription factors (35,67). It has been suggested that both ElA proteins share domains which may suppress the expression of viral and cellular enhancer-dependent promoters (11,28,52,59) and that both proteins are necessary for the induction of cellular DNA synthesis and cell proliferation (33,38,49,53). Both proteins are required to establish and maintain the transformed cell phenotype by using primary or continuous cultures of rodent cells (25,30,32,40,43,51,69).…”

Establishment and characterization of adenoviral E1A immortalized cell lines derived from the rat suprachiasmatic nucleus

“…In attempt to institute this strategy, gene transfer techniques were used to mediate the introduction of an oncogene and expression of its immortalizing protein product in primary SCN cells, because this method has yielded many useful cell lines with stable growth characteristics and parental phenotypic properties (Cepko, 1988(Cepko, , 1989(Cepko, , 1990. The capacity of the adenoviral early-region 1A (E1A) gene to immortalize progenitors of the rat SCN was explored in the present experiments because the 12S protein product of this oncogene induces DNA syn-thesis and extends the growth potential of primary cells derived from a variety of rat tissues (Quinlan and Grodzicker, 1987;Cone et al, 1988;Ryder et al, 1990;Seigel, 1996). The results reported here indicate that transfer of the 12S E1A gene into primary SCN cells in culture using retroviral vector constructed by Cone and coworkers (1988) yields growth-stimulated cell lines that express glial as well as neuronal phenotypes.…”

The Replicative Capacities of Large E1B-Null Group A and Group C Adenoviruses Are Independent of Host Cell p53 Status

“…E1A interacts with a number of cellular proteins important in regulating cell growth (8,29,49). They function predominantly as transcriptional adapters or are integral components of the transcriptional machinery, regulating transcription from both viral early and cellular promoters (11,37).…”