Immortalization of rat embryo fibroblasts by an adenovirus 2 mutant expressing a single functional E1a protein

Chimeric adenovirus type 5 (Ad5)/Adl2 early region IA (EIA) genes were used to transform primary baby rat kidney cells in cooperation with Adl2 E1B, and the resulting cell lines were assayed for tumorigenicity in syngeneic rats. It was found that lines were nontumorigenic when transformed by hybrid ElA genes consisting of the amino-terminal 80 amino acids from Adl2 including conserved region 1 (CR1), with the remaining portion from Ad5. In contrast, cell lines transformed by hybrids containing Adl2 EIA sequences from the amino terminus to the leftmost border of CR3 or beyond were tumorigenic. To extend these results, sequences spanning CR2 and CR3 of Ad5 ElA were replaced with the homologous regions of Adl2 EIA and additional transformed cell lines were established. These lines were weakly-to-moderately tumorigenic, suggesting that Adl2 EIA sequences between CR2 and CR3 may be involved in tumorigenicity but are not the sole factors influencing it. Interestingly, examination of an ElA sequence alignment indicated that the region between CR2 and CR3 of Adl2 EIA is also conserved in the corresponding sequence of simian adenovirus type 7, which, like Adl2, is highly oncogenic. This region is characterized by the presence of a stretch of several alanine residues and is similar to a motif present in a number of proteins with transcriptional repression activity. The possibility that this region may influence tumorigenicity by means of a transcriptional regulatory mechanism is discussed.

Section: Residuementioning

confidence: 94%

Tumorigenicity of adenovirus-transformed rodent cells is influenced by at least two regions of adenovirus type 12 early region 1A

Jelı́nek

Pereira

Graham

1994

“…These two proteins have been implicated to different degrees in the various functions attributed to region Ela. Both Ela gene products play roles in the transformation of rodent cells (16,19,26,41). The larger protein (289R protein) is necessary (4, 9, 30) and sufficient (27) for the enhancement of early viral gene expression during infection, but the smaller protein (243R protein) enhances viral DNA replication in growth-arrested cells (34).…”

mentioning

confidence: 99%

Differential nuclear localization of the major adenovirus type 2 E1a proteins

Schmitt¹,

Fahnestock²,

Lewis³

1987

The localization in infected and transformed cells of the two major adenovirus type 2 Ela proteins, of 289 and 243 amino acid residues, was studied with antisera raised against synthetic peptides or a TrpE-Ela fusion protein. Both Ela proteins were detected only in the nucleus of infected cells as determined by immunofluorescence analysis of cells infected with wild-type virus or with the mutants pm975 or d11500, which produce, respectively, only the 289-residue or only the 243-residue Ela protein. However, the 289-residue protein was more tightly associated with the nucleus than was the 243-residue protein, as determined by the stability of nuclear fluorescence to different fixation procedures and by the use of radioimmunoprecipitation and Western blot analysis to analyze fractions extracted from the nucleus by detergent and other treatments. The latter experiments revealed that only the 289-residue protein, and only a fraction of that protein present in the nucleus, is associated with the nuclear matrix, both in infected HeLa cells and in the transformed human cell line 293.

“…In transformed cells and at early times after infection, two families of ElA products are detected that are translated from two overlapping ElA mRNAs (13S mRNA and 12S mRNA) that differ only by the sizes of the introns removed during posttranscriptional processing. Expression of these ElA proteins is associated with several functions including either activation or repression of viral and cellular gene transcription (reviewed in reference 3), stimulation of viral and cellular DNA replication (24, 29), establishment of transformation (15,20), viral specificity of transformed cell tumor-specific transplantation antigen (26), and induction of susceptibility of virus-infected (5) and virus-transformed (6) cells to the cytolytic effects of NK cells and activated macrophages. Studies of the intracellular localization of ElA proteins indicate that proteins that contain the carboxyterminal 5 amino acids encoded by the ElA gene localize to the nucleus (19).…”

Section: Resultsmentioning

confidence: 99%

“…The viral protein components of CTL target structures in these studies appeared to map to adenovirus early transcriptional regions 1 (El [25]) and 3 (E3 [18]). The adenovirus El region comprises the ElA and E1B genes and encodes nonstructural viral proteins that are involved in viral transcription, replication, and transformation of mammalian cells (15,20,23). Although ElA proteins have not been reported to be associated with cell membranes, the E1B 15-kilodalton protein and a 19-kilodalton protein encoded by the E3 gene have been associated with membranes in adenovirus-infected and transformed cells, and the E3 19-kilodalton protein has been shown to be associated with the cellular class I major histocompatibility antigen (18,22).…”

mentioning

confidence: 99%

Recognition of adenovirus E1A gene products on immortalized cell surfaces by cytotoxic T lymphocytes

Bellgrau

Walker

Cook

1988