Biochemical characterization of protein kinase activities associated with transforming gene products of the Snyder-Theilen and Gardner-Arnstein strains of feline sarcoma virus

Nucleic acid sequence and oncogenic properties of the HZ2 feline sarcoma virus v-abl insert

Hardy-Zuckerman 2 feline sarcoma virus (HZ2-FeSV), isolated from a multicentric feline fibrosarcoma is a replication-defective acute transforming feline retrovirus which originated by transduction of feline c-abl sequences with feline leukemia virus (FeLV) and is known to encode a 110-kilodalton gag-abl fusion protein with tyrosine-specific protein kinase activity (P. Besmer, W. D. Hardy, E. E. Zuckerman, P. J. Bergold, L. Lederman, and H. W. Snyder, Nature (London) 303:825-828, 1983). The nucleotide sequence of the abl segment in the HZ2-FeSV genome was determined and compared with the murine and human v-abl and c-abl sequences. The predicted transforming protein consists of 344 amino acids (aa) of FeLV gag origin, 439 aa of abl origin, and at least 200 aa of FeLV pol origin (p110gag-abl-pol). The 1,317-base-pair HZ2-FeSV v-abl segment (fv-abl) corresponds to 5' abl sequences which include the region known to specify the protein kinase domain. The 5' 189 base pairs of fv-abl correspond to 5' c-abl sequences not contained in Abelson murine leukemia virus (MuLV) v-abl. The mouse c-abl exon which contains these segments was identified, and its nucleotide sequence was determined. Comparison of the predicted amino acid sequence of fv-abl with those of Abelson MuLV v-abl and c-abl revealed five aa differences. The 5' junction between FeLV and abl was found to involve a preferred region in FeLV gag p30 (P. Besmer, J. E. Murphy, P. C. George, F. H. Qiu, P. J. Bergold, L. Lederman, H. W. Snyder, D. Brodeur, E. E. Zuckerman, and W. D. Hardy, Nature (London) 320:415-421, 1986). A six-base homology exists at the recombination site between the parental FeLV and the c-abl sequences. The 3' junction between fv-abl and FeLV pol predicts an in-frame fusion of fv-abl and FeLV pol. A transformed cell line containing a truncated gag-abl-pol protein, p85, that lacks most of the FeLV pol sequences was obtained by transfection of NIH 3T3 mouse cells. This result implies that the pol sequences of the p110gag-abl-pol protein are dispensable for fibroblast transformation. To assess whether the fv-abl segment specifies the unique biological properties of HZ2-FeSV, we constructed a Moloney MuLV-based version of HZ2-FeSV, Mo-MuLV(fv-abl), in which the fv-abl sequences were contained in a genetic context similar to that in HZ2-FeSV.(ABSTRACT TRUNCATED AT 400 WORDS)

Isolation of a new feline sarcoma virus (HZ1-FeSV): biochemical and immunological characterization of its translation product

A new strain of feline sarcoma virus, designated HZ1-FeSV, was isolated from a 4-year-old domestic cat with multicentric fibrosarcoma. A primary tumor cell line was established and virus produced from that line was found to induce foci in feline embryonic lung fibroblasts (FLF3) and mink lung fibroblasts (CCL64) in tissue culture and fibrosarcomas in inoculated 10-week-old kittens. The derivation of transformed nonproducer clones of FLF3 and CCL64 cells containing helper virus-rescuable, focus-forming activity indicated that HZ1-FeSV was defective for replication. The only discernible translation product of the HZ1-FeSV genome in cultured cells was a 100,000-Da polyprotein (P100) which contained amino-terminal sequences of the FeLV gag gene precursor protein covalently linked to a sarcoma virus-specific domain. Immunoprecipitates containing P100 exhibited a protein kinase activity capable of phosphorylating tyrosine residues of P100. Immunologically, P100 was highly cross-reactive with gag-fes polyproteins encoded by two previously characterized strains of FeSV, the GA- and the ST-FeSV. By comparison of methionine-containing tryptic peptides, the HZ1-FeSV protein was shown to be more closely related to the GA-FeSV protein than to the ST-FeSV protein, but to be distinguishable from both other proteins.

The Hardy-Zuckerman 2-FeSV, a new feline retrovirus with oncogene homology to Abelson-MuLV

There is substantial evidence that oncogenes (v-onc) of acute transforming retroviruses have been acquired by transduction of cellular genes (c-onc) with retroviruses. Feline leukaemia virus (FeLV)-associated feline fibrosarcomas have proven to be extremely useful for the isolation of acute transforming retroviruses of a mammalian species. Three different v-onc genes have been identified in five acute transforming feline retroviruses. The Susan McDonough feline sarcoma virus (SMFeSV) contains the oncogene fms (ref. 4). The Snyder-Theilen (ST) and Gardner-Arnstein (GA) FeSVs contain the oncogene fes (ref. 4), which is homologous to the oncogene fps of the avian sarcoma viruses FSV, RRCII, PRCIV and 16L (refs 7, 8). The v-onc sequences of the Parodi-Irgens (PI) FeSV have recently been found to be homologous with the v-sis sequences of the simian sarcoma virus. We report here the isolation of another acute transforming feline retrovirus from a naturally occurring feline fibrosarcoma, designated the Hardy-Zuckerman 2 feline sarcoma virus (HZ2-FeSV) and demonstrate that the HZ2-FeSV and Abelson murine leukaemia virus (A-MuLV) have homologous oncogenes.

The Parodi-Irgens feline sarcoma virus and simian sarcoma virus have homologous oncogenes, but in different contexts of the viral genomes

We have identified the oncogene and the putative transforming protein of the Parodi-Irgens feline sarcoma virus (PI-FeSV). The PI-FeSV is defective and needs a helper virus for its replication. The v-onc sequences in the PI-FeSV were found to be related to the v-sis sequences of the simian sarcoma virus (SSV). PI-FeSV nonproducer cells express two viral RNAs, a 6.8-and a 3.3-kilobase RNA. The 6.8-kilobase RNA contains gag, sis, and env sequences but lacks the pol gene. The 3.3-kilobase RNA, on the other hand, contains only env sequences. We have detected one feline leukemia virus-related protein product in these cells, namely, a 76-kilodalton protein which contains determinants of the feline leukemia virus gag proteins p15 and p30. The v-sis sequences in the PI-FeSV have been located near the 5' end of the viral genome. Taken together, these results imply that the p76 protein contains both feline leukemia virus gag and sis sequences and probably is the transforming protein of this virus. In contrast, in SSV the sis sequences are located towards the 3' end of the viral genome, and the sis protein is thought to be expressed via a subgenomic RNA. PI-FeSV and SSV therefore use different schemes to express their onc-related sequences. The v-sis sequences in the PI-FeSV contain restriction sites which reflect the different origin of the v-sis sequences in the PI-FeSV and SSV. The homologous oncogenes of the PI-FeSV and SSV thus were transduced by two different retroviruses, feline leukemia virus and the simian sarcoma-associated virus, apparently from the genomes of different species.

Feline sarcoma virus-specific transformation-related proteins and protein kinase activity in tumor cells

Polyproteins (gag-fes) encoded by the Synder-Theilen (ST) and the Gardner-Arnstein (GA) strains of feline sarcoma virus (FeSV) were previously shown to be associated with mink or rat cells that were nonproductively transformed in vitro. In the present study we demonstrated that the same gag-fes proteins were found in cat cells transformed in vitro. Of greater importance, these transformation-related proteins were also in cells taken from fresh biopsies of FeSV-induced tumors. Cells from fibrosarcomas induced with ST-FeSV had gag-fes proteins that were characteristic of this strain. Fibrosarcomas and melanomas were induced with GA-FeSV and both types of tumors contained the protein that is characteristic of cells transformed in vitro with this virus. Expression of these proteins in cultured tumor cells appeared to be independent of the passage level. Based on two-dimensional tryptic peptide analysis, the gag-fes proteins of cat tumor cells appeared to be indistinguishable from those found in cells transformed in vitro. The polyproteins of the cat tumor cells have a closely associated protein kinase activity, as demonstrated in the in vitro assay, and phosphorylated tyrosine residues. Gag-fes proteins of either the ST or GA class were not present in cell cultures initiated from five spontaneous cat tumors.

Association of the transforming proteins of the ST and GA strains of feline sarcoma virus and their in vitro associated protein kinase activities with cellular membranes

The translation products of the Snyder-Theilen (ST) and Gardner-Arnstein (GA) strains of feline sarcoma virus (FeSV), termed gag-fes proteins, are high molecular weight polyproteins containing different amounts of the amino terminus of the feline leukemia virus (FeLV) gag gene-coded precursor protein linked to a similar sarcoma virus-specific polypeptide. Both polyproteins are phosphoproteins with indistinguishable in vitro associated tyrosine-specific protein kinase activities. The polyproteins are extremely hydrophobic proteins which are intimately associated with the plasma membrane fraction of transformed cells. Approximately 10% of the proteins are modified by glycosylation and expressed on the cell surface where they are accessible to lactoperoxidase-mediated radio-iodination and trypsinization. Cell surface localization of the polyproteins does not appear to be necessary for transformation. However, preliminary evidence suggests that the amount of FeLV p30 sequences at the amino end of the proteins may have some effect on the intracellular distribution of the gag-fes polyproteins and on the phenotype of the transformed cell.

Detection and localization of a phosphotyrosine-containing onc gene product in feline tumor cells

Protein phosphorylation by a tyrosine-specific kinase is now recognized as a common event in retrovirus-transformed cells. We report in this communication that the feline sarcoma virus (FeSV) encoded transformation-specific proteins (gag-fes fusion proteins) and their associated protein kinases are also found in the FeSV in vivo induced tumor preparations, either in the form of fresh tumor homogenate or in the form of cultured cells. With the combined use of subcellular fractionation and detergent extraction we found that the protein kinase activity was present in both the membrane fraction (P100) and the cytosol (S100). The gag-fes proteins of two different strains of FeSV were found to associate with the cell framework to different degrees, suggesting that the specific conformational presentation of these proteins may be dictated by the unique portion of each polyprotein. The same gag-fes transformation related proteins could be immunoprecipitated with antiserum to phosphotyrosine.