Feline sarcoma virus-coded polyprotein: enzymatic cleavage by a type C virus-coded structural protein

An erythroleukemia cell clone, 7C, which failed to produce reverse transcriptase-containing virions or infectious virus, was found to produce noninfectious virus particles by gradient banding of [3H]leucineand [3H]uridine-labeled virions. The RNA from the 7C virus was shown to consist of the normal 70S size component, which converted to 35S upon heat denaturation. In contrast, the 7C virion proteins showed multiple defects. Analysis of the virion proteins by gel electrophoresis demonstrated that the pr65 gag precursor was incorporated into the 7C virus and that the processing of this precursor was severely diminished. Polymerase proteins pr18O9a9-)" and prl2OPI' were also detected in virions, and a third possible polymerase protein, p70, was reduced in size compared to its normal counterpart, p80. Incorporation of the viral gp7O glycoprotein into particles was also reduced 10-fold, despite synthesis and incorporation of gp7O into the 7C cell membrane in normal amounts. Pulse-chase analysis of the synthesis of the viral gag and env proteins in 7C cells showed greatly reduced amounts of prl80g ,,OI,

Section: Resultsmentioning

confidence: 99%

Replication-defective Friend murine leukemia virus particles containing uncleaved gag polyproteins and decreased levels of envelope glycoprotein

Collins¹,

Chesebro²

1981

“…However, the only processing agent (molecular weight, 10,000 to 12,000) identified in murine retrovirions is present in only trace amounts and has no known relationships to any of the four murine gag gene proteins (40). It might correspond to a fifth murine gag protein which is translated only rarely, for example, as a read-through product (18); alternatively, the murine viral protease gene may have been deleted and its function may have been replaced by a host enzyme.…”

Section: Resultsmentioning

confidence: 99%

Novel p19-related protein in Rous-associated virus type 61: implications for avian gag gene order

Shealy¹,

Mosser²,

Rueckert³

1980

Virions of Rous-associated virus type 61 contain a previously unrecognized p19related protein, called pl9f, which comigrates with gag protein p12 during electrophoresis in sodium dodecyl sulfate-polyacrylamide gels but can be separated by gel filtration chromatography in 6 M guanidine hydrochloride. It is shown that the existence of pl9f accounts for the earlier inability to order p27 and p12 by the pactamycin mapping procedure. Remapping with pactamycin by using methods which take this new protein into account yielded a gag gene order of NH2-p19-p27-p12-p15-COOH. It also confirmed earlier positions for the env and pol genes and placed unclassified protein plO near a translational initiation site. The pactamycin-derived mapping position of p12 differs from reports based on tryptic analysis. An analysis of procedural shortcomings emphasizes the need for more definitive determinations of the avian gag gene order. Nondefective avian retroviruses contain the following three genes: gag, which codes for group-specific antigens p27, p19, p12, and p15, which are found in the virion core; pol, which codes for the a(p64) and f,(p9l) subunits of the

“…Competition immunoassays were performed by analyzing unlabeled antigens at serial twofold dilutions for their ability to compete with "2I-labeled FeLV p30, p15, p12, plO, and gp7O for binding limiting amounts of goat antiserum directed against detergent-disrupted FeLV. Proteins were purified and labeled with "1I according to previously described procedures (11). Competition immunoassay reaction mixtures contained 0.01 M Tris-hydrochloride (pH 7.8), 1.0 mM EDTA, 0.4% Triton X-100, 1% bovine serum albumin, and 0.2 M NaCl in a total volume of 0.2 ml.…”

Section: University Of Southern California Isolates Of Felvmentioning

confidence: 99%

“…Antiserum and unlabeled competing antigen were incubated at 37°C for 1 h; this was followed by the addition of 10,000 cpm of "MI-labeled antigen. After further incubation for 3 h at 37°C and 18 h at 4°C, antigen-antibody complexes were immunoprecipitated as previously described (11).…”

Section: University Of Southern California Isolates Of Felvmentioning

confidence: 99%

Translational products encoded by newly acquired sequences of independently derived feline sarcoma virus isolates are structurally related

Ven¹,

Khan²,

Reynolds³

et al. 1980

Self Cite

Polyproteins encoded by several independent isolates of feline sarcoma virus (FeSV) were analyzed with respect to molecular weight, extent of phosphorylation, and tryptic peptide composition. As previously reported, cells nonproductively transformed by the Gardner strain of FeSV express a polyprotein which has a molecular weight of approximately 115,000 and contains feline leukemia virus p15, p12, and minor portion of p30. In addition, a major 72,000-dalton possible cleavage product can be identified. Snyder-Theilen FeSV-transformed cells express a major polyprotein of approximately 115,000 daltons and a second highly related 80,000-dalton protein. The p12 structural component of Gardner FeSV P115, but not Snyder-Theilen FeSV 115, corresponds to feline leukemia virus subgroup A with respect to immunological type specificity, a finding consistent with the independent origin of these viruses. Tryptic peptide analysis revealed five methionine-containing peptides specific to the nonstructural portion of Gardner FeSV 115, three of which were also represented in Snyder-Theilen FeSV P115, three of which were also represented in Snyder-Theilen FeSV P115. None of these [35S]methionine-labeled tryptic peptides were present in translational products representative of the complete feline leukemia virus subgroup A genome, including Pr180gag-pol, Pr65gag, and Pr82env. Similarly phosphorylated tryptic peptides within the structural (p12) and nonstructural components of Gardner FeSV P115 and Snyder-Theilen FeSV P115 Are highly related. These findings support the possibility that acquired sequences of two independently derived isolates of FeSV encode structurally related proteins.