Immunological identification of two adenovirus 2-induced early proteins possibly involved in cell transformation

Purification and characterization of an early protein (E14K) from adenovirus type 2-infected cells

One adenovirus type 2 (Ad2) early protein, with an apparent molecular weight of 14,000 in sodium dodecyl sulfate-polyacrylamide gels (E14K), was purified to homogeneity. Purification involved fractionation of cytoplasmic extracts, precipitation at low pH, and DEAE-cellulose, phosphocellulose, and hydroxylapatite chromatography. The yield was around 12 microgram of purified protein per 10(9) HeLa cells. The two Ad2 DNA binding proteins with molecular weights of 75,000 and 45,000 (E75K and E45K) were purified by the same procedure. Tryptic peptide analyses indicated that the E14K protein is unrelated to the DNA binding proteins. The purified E14K protein has a high content of basic amino acids and a sedimentation coefficient of 5.5S in the native state, corresponding to a molecular weight of around 95,000. Pulse-chase experiments suggest that the E14K polypeptide is a primary translation product. Immunoprecipitation with a monospecific antiserum against the E14K protein revealed that it is exclusively localized in the cytoplasm of infected cells. E14K started to be synthesized at 2 hpostinfection, with a maximal rate of synthesis at 4 to 6 h postinfection. Immunoprecipitation of cell extracts from four different Ad2-transformed hamster embryo cell lines revealed that only one (Ad2HE4) of them expresses this protein. The adenovirus-simian virus 40 hybrid virus (Ad2ND1) does not express this protein, suggesting that the gene for the E14K protein is located in the part of the Ad2 genome which is deleted in this hybrid virus.

Viral DNA sequences and gene products in hamster cells transformed by adenovirus type 2

Complementary strand-specific adenovirus DNA of full length or from endonuclease BamHI fragments was used as a probe to estimate the fractional representation and abundance of viral sequences in five hamster cell lines (Ad2HE1-5) transformed with UV-inactivated adenovirus type 2. The fraction of the viral genome present in the five transformed cell lines varied from 44% in the Ad2HE5 cell line to 84% in the Ad2HE3 cell line. The number of viral DNA copies per diploid cell equivalent ranged from 1.8 in the Ad2HE1 line to 7.1 in the Ad2HE4 line. In vivo labeling with [35S]methionine followed by immunoprecipitation with an antiserum against adenovirus type 2 early proteins revealed virus-specific polypeptides with molecular weights of 42,000 to 58,000 in extracts from all five hamster cell lines. Several other early viral polypeptides were detected in some of the adenovirus type 2-transformed hamster cell lines.

Adenovirus type 2 early proteins synthesized in vitro and in vivo: identification in infected cells of the 38,000- to 50,000- molecular-weight protein encoded by the left end of the adenovirus type 2 genome

Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of protein synthesized early after injection of human cells with adenovirus type 2 (Ad2) showed that polypeptides of 11,000 (11K), 12K, 14K, 15K, 19K, 21K, 24K, and 72k molecular weight were present in infected but not in mock-infected cells. These polypeptides corresponded in electrophoretic mobility to the following polypeptides synthesized in vitro by using mRNA complementary to specific regions of the Ad2 genome: 11K, 19K, 21K (91.5 to 96.8 map units), 14K (78.2 to 83.4 map units), 72K (62.4 to 67.9 map units), and 15K (4.9 to 11.0 map units). Polypeptides of 25K, 17K, 15.5K, and 13K were also synthesized in vitro, but have not yet been detected in infected cells. In addition, six adeno-specific polypeptides of 38 to 50K molecular weight could be discerned in infected cells if two-dimensional isoelectric focusing-polyacrylamide gel electrophoresis was used to compare extracts from infected and mock-infected cells. Partial protease digestion showed these 38 to 50K polypeptides to be related in sequence to each other and to the 40 to 50K polypeptide made in vitro (1.3 to 4.0 map units).