Involvement of a high-molecular-weight polyprotein translational product of Snyder-Theilen Feline sarcoma virus in malignant transformation

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The nucleotide sequence of the feline c-fes/fps proto-oncogene was analyzed. Comparison with v-fes and v-fps revealed that all v-feslfps homologous sequences were dispersed over 11 kilobase pairs in 19 interspersed segments. All segments, numbered exon 1 to exon 19 as in the chicken and human loci, were flanked by consensus splice junctions. The putative promoter region contained a CATT sequence and three CCGCCC motifs which were also found in the human locus at similar positions. About 200 nucleotides downstream of a translational stop codon in exon 19, a putative poly(A) addition signal was identified. Using the putative translation initiation codon in exon 2, a 93,000-molecular-weight protein could be deduced. This protein resembled very well the putative protein of the human c-feslfps proto-oncogene (94% overall homology) and, although less well, the putative protein of the chicken c-feslfps proto-oncogene (70% overall homology). As far as the feline c-feslfps proto-oncogene sequences transduced to the Gardner-Arnstein (GA) and Snyder-Theilen (ST) strains of feline sarcoma virus (FeSV) are concerned, homology in deduced amino acid sequences between the GA-and ST-v-fes viral oncogenes and the proto-oncogene was 99%. Analysis of the recombination junctions between feline leukemia virus and v-fes sequences in GA-and ST-FeSV proviral DNA revealed for the left-hand junction the involvement of homologous recombination, presumably at the DNA level. The right-hand junction, which appeared identical in the GA-FeSV and ST-FeSV genomes, could have been the result of a site-specific recombination at the RNA level.

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confidence: 99%

Structure of the feline c-fes/fps proto-oncogene: genesis of a retroviral oncogene

Roebroek¹,

Schalken²,

Onnekink³

et al. 1987

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“…The v-fes sequences of each genome contain similar, but nonidentical, elements (13) derived from a segmented cat cellular gene (c-fes) (14). The gag and v-fes sequences encode fusion polyproteins (4,38,43,50,53) which exhibit an associated tyrosine-specific protein kinase activity (2,55) necessary for transformation (3,9,40). By contrast, the structure of the SM-FeSV genome has remained unclear, and v-fms sequences have not been characterized either with respect to their organization or function.…”

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confidence: 99%

McDonough feline sarcoma virus: characterization of the molecularly cloned provirus and its feline oncogene (v-fms)

Donner¹,

Fedele²,

Garon³

et al. 1982

194

The genetic structure of the McDonough strain of feline sarcoma virus (SM-FeSV) was deduced by analysis of molecularly cloned, transforming proviral DNA. The 8.2-kilobase pair SM-FeSV provirus is longer than those of other feline sarcoma viruses and contains a transforming gene (v-fms) flanked by sequences derived from feline leukemia virus. The order of genes with respect to viral RNA is 5'-gag-fms-env-3', in which the entire feline leukemia virus env gene and an almost complete gag sequence are represented. Transfection of NIH/3T3 cells with cloned SM-FeSV proviral DNA induced foci of morphologically transformed cells which expressed SM-FeSV gene products and contained rescuable sarcoma viral genomes. Cells transformed by viral infection or after transfection with cloned proviral DNA expressed the polyprotein (P1700ag-fms) characteristic of the SM-FeSV strain. Two proteolytic cleavage products (Pl2OfmS and pp55sag) were also found in immunoprecipitates from metabolically labeled, transformed cells. An additional polypeptide, detected at comparatively low levels in SM-FeSV transformants, was indistinguishable in size and antigenicity from the envelope precursor (gPr85env) of feline leukemia virus. The complexity of the v-fms gene (3.1 ± 0.3 kilobase pairs) is approximately twofold greater than the viral oncogene sequences (v-fes) of Snyder-Theilen and Gardner-Arnstein FeSV. By heteroduplex, restriction enzyme, and nucleic acid hybridization analyses, v-fms and v-fes sequences showed no detectable homology to one another. Radiolabeled DNA fragments representing portions of the two viral oncogenes hybridized to different EcoRl and HindIII fragments of normal cat cellular DNA. Cellular sequences related to v-fms (designated c-fms) were much more complex than c-fes and were distributed segmentally over more than 40 kilobase pairs in cat DNA. Comparative structural studies of the molecularly cloned proviruses of Snyder-Theilen, Gardner-Arnstein, and SM-FeSV showed that a region of the feline leukemia virus genome derived from the pol-env junction is represented adjacent to v-onc sequences in each FeSV strain and may have provided sequences preferred for recombination with cellular genes.

“…The major translational products of such isolates are in each case high-molecular-weight (>100,000) polyproteins consisting of type C virus structural and acquired sequence-encoded components (2, 12,21,25,30,31). In the case of one of these isolates, Snyder-Theilen feline sarcoma virus (FeSV), two variants have been reported, one encoding a major polyprotein of 115,000 Mr (30) and the second encoding an 85,000Mr polyprotein (2, 16,21). McDonough FeSV and Gardner FeSV encode as their major translational products polyproteins of 170,000 Mr (2, 31) and 115,000 Mr (25,30), respectively.…”

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confidence: 99%

“…In the case of Snyder-Theilen FeSV, this involves a single tyrosine acceptor site within the polyprotein (4). The availability of transformation-defective mutants has made possible the demonstration that these virus-encoded polyproteins and their associated NOTES 1085 protein kinase activities have transforming function (16). Finally, a 150,000-Mr cellular protein kinase with specificity for serine and threonine has been shown to exhibit binding affinity for Gardner FeSV P115 (17) and to represent a substrate for its associated tyrosine-specific protein kinase activity (18).…”

mentioning

confidence: 99%

“…Cell lines have been described previously (16,31) and include Gardner FeS V-transformed mink (64 FeSV) (A through D), Snyder-Theilen FeSV-transformned rat (ST-NRK) (E through H), Snyder-Theilen FeS V-transformned mink (ST-FeSV 64 Cl 56) (I through L), and McDonough FeSV-transformed mink (McD-FeSV Cl 15-1) (M through P). Metabolic labeling of exponentially growing cells for 2 h at 370C with "4Camino acids (10 jiCi/ml; 57 mCi/milligramatom; Amersham Corp., Arlington Heights, Ill.), immunoprecipitation by either goat anti-feline leukemia virus (A, E, I, and M) or control goat serum (B, F, J, and N), and analysis of immunoprecipitates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were performed as reported previously (16). For protein kinase assays, unlabeled cells were disrupted by repeated aspiration of i0' cells in 5 ml of 10 mM sodium phosphate (pH 7.2)-100 mM NaCl-1.09% Triton X-1XJ-5 mM MgCl2 (PBSTM) through a 25-gauge needle.…”

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confidence: 99%

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Differences in mechanisms of transformation by independent feline sarcoma virus isolates

Reynolds¹,

Ven²,

Blomberg³

et al. 1981

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The Gardner and Snyder-Theilen isolates of feline sarcoma virus (FeSV) have previously been shown to encode high-molecular-weight polyproteins with a transforming function and an associated tyrosine-specific protein kinase activity. Cells transformed by these viruses exhibited morphological alterations, elevated levels of phosphotyrosine, and a reduced capacity for binding epidermal growth factor. In addition, polyproteins encoded by both of these FeSV isolates bound to, and phosphorylated tyrosine acceptor sites within, a 150,000-molecular-weight cellular substrate (P150). McDonough FeSV-transformed cells resembled Gardner and Snyder-Theilen FeSV transformants with respect to morphological changes and a reduced capacity for epidermal growth factor binding. in contrast to the other two FeSV isolates, however, McDonough FeSV encoded as its major translational product a high-molecular-weight polyprotein with probable transforming function but without protein kinase activity detectable under similar assay conditions. Moreover, total cellular levels of phosphotyrosine remained unaltered in McDonough FeSV-transformed cells, and the major McDonough FeSV polyprotein translational product lacked binding affinity for P150. These findings argue for differences in the mechanisms of transformation by these independently derived FeSV isolates.