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J C Neil

Publications and source records attributed to J C Neil.

105 records · Page 6Linked to original sources
PubMed1981

PRCII, a representative of a new class of avian sarcoma viruses.

The Poultry Research Center Virus II (PRC II) is a replication-defective avian sarcoma virus with envelope determinants of the A and B subgroups. In nonproducing cells transformed by PRCII the products of the replicative genes gag, pol, and env are not demonstrable, but a single polyprotein of Mr 105,000 (p105) can be detected. P105 contains peptides of the gag proteins p19 and p27 plus transformation-specific sequences. It does not contain peptides of gPr95env of Pr180gag-pol (with the possible exception of one pol peptide). The transformation-specific sequences of p105 are distinct form those of p100 of avian carcinoma virus MH2, of p110 coded for by avian myelocytoma virus MC29, and of p75 or p40 of avian erythroblastosis virus AEV. They also show no resemblance to p60src of Rous sarcoma virus. P105 is phosphorylated on a tyrosine residue and has an associated phosphokinase activity. P105 appears to be capable of autophosphorylation and of phosphorylating homologous immunoglobulin.

Alpharetrovirus↗
PubMed1981

Evidence for three classes of avian sarcoma viruses: comparison of the transformation-specific proteins of PRCII, Y73, and Fujinami viruses.

The gag-linked transformation-specific proteins (polyproteins( of PRCII, Fujinami, and Y73 avian sarcoma viruses have been compared by tryptic peptide mapping. In addition to shared gag peptides, PRCII polyprotein p105 and FSV polyprotein p140 were found to have seven methionine-containing and five cysteine-containing tryptic peptides in common. These represent the majority of the non-gag peptides for each virus. In contrast, no overlap was detected with the non-gag peptides of the Y73 polyprotein p90. Examination of the tryptic phosphopeptides of p105, p140, and p90 labeled by their associated protein kinases gave similar results. Although the major phosphopeptides of p105 and p140 comigrated, they were distinct from the phosphopeptide of p90. Three classes of transformation-specific proteins can now be identified among known avian sarcoma viruses. After the pp60src of Rous sarcoma virus and B77 virus, the proteins of PRCII and Fujinami virus form a second class and Y73--currently the only representative--characterizes the third. Despite their structural differences, these viruses may share a common mechanism of transformation, effected by their associated protein kinases.

Alpharetrovirus↗
PubMed1981

A third class of avian sarcoma viruses, defined by related transformation-specific proteins of Yamaguchi 73 and Esh sarcoma viruses.

The gag-linked transformation-specific protein (polyprotein) p80 of Esh avian sarcoma virus (ESV) has been compared by tryptic peptide mapping with the homologous protein p90 of Yamaguchi 73 avian sarcoma virus (Y73). p80 of ESV and p90 of Y73 were found to share all four of their major nonstructural, transformation-specific, methionine-containing peptides and to have at least seven cysteine-containing transformation-specific peptides in common. Two nonstructural cysteine-containing peptides unique for ESV p80 and three specific for Y73 p90 were also identified. None of these peptides were found in the transforming gene product pp60src of Rous sarcoma virus (RSV) or in the transformation-specific polyproteins p105 of avian sarcoma virus PRCII (PRCII) or p140 of Fujinami sarcoma virus (FSV). ESV p80 and Y73 p90 are phosphorylated, and their tryptic phosphopeptides appear to be identical. In each polyprotein two major phosphopeptides were demonstrated, one containing phosphoserine, the other phosphotyrosine. The latter serves as phosphoacceptor for the protein kinase activities (ATP:protein phosphotransferase, EC 2.7.1.37) associated with p80 and p90. These protein kinase activities were found to be functionally indistinguishable but could be easily distinguished from the activities associated with PRCII p105 and FSV p140 on the basis of their cation requirement and target site specificity. On that basis also, p80/p90-associated protein kinases were found to be more similar to the enzymatic activity of pp60src than to those associated with the PRCII and FSV transformation-specific polyproteins. These results document a close genetic relationship between the two independently isolated sarcoma viruses Y73 and ESV. On the basis of the relatedness of transformation-specific proteins, ESV and Y73 constitute class III of avian sarcoma viruses, with class I containing the various strains of RSV and class II encompassing FSV and PRCII.

Alpharetrovirus↗
PubMed1981

Cleavage of four avian sarcoma virus polyproteins with virion protease p15 removes gag sequences and yields large fragments that function as tyrosine phosphoacceptors in vitro.

The transformation-specific polyproteins of avian sarcoma viruses PRCII, PRCII-p, Fujinami sarcoma virus (FSV), and Esh sarcoma virus (ESV) consist of two domains, one derived from a partial viral gag gene and the other representing an apparently cell-derived insert in the defective viral genome. These gag-linked proteins were cleaved with retrovirion protease p15. Cleavage of PRCII-p polyprotein P170, P105 of PRCII, and P140 of FSV occurred within the gag domain and generated fragments of Mr 130,000, 70,000, and 115,000, respectively, containing all of the transformation-specific sequences linked to a remnant of the original gag sequences. ESV P80 was cleaved inside the transformation-specific domain, yielding a Mr 35,000--38,000 fragment from the NH2-terminal half of the molecule consisting of the entire gag portion and some no-gag sequences and a Mr 48,000 fragment containing most of the transformation-specific sequences. The tyrosine phosphorylation sites of the polyproteins were found in every case in the transformation-specific fragments. The major serine phosphorylation site of ESV P80 was found to reside in the Mr 35,000--38,000 gag-containing fragment, probably within the transformation-specific sequences of that cleavage product. Removal of all of the gag domain of ESV P80 or most of the gag domain in PRCII-p P170, PRCII P105, and FSV P140 does not affect their ability to be phosphorylated by the polyprotein-associated tyrosine-specific protein kinase activities. This observation suggests that the gag sequences of the polyproteins of classes II (PRCII-p, PRCII, and FSV) and III (ESV) avian sarcoma viruses may not be required for this enzymatic function, which appears to be of importance in transformation.

Alpharetrovirus↗
PubMed1980

Polypeptides of feline leukaemia virus: identification of p15(E) and p12(E).

Antiserum to the p15(E) polypeptide of Rauscher murine leukaemia virus (R-MuLV) precipitated two proteins from purified virions of feline leukaemia virus (FeLV) with apparent mol. wt. of 18500 and 155000 on SDS-polyacrylamide gels. These proteins have been designated p15(E) and p12(E), in line with the nomenclature for MuLV proteins. Like the analogous protein of MuLV, FeLV p15(E) was found to be disulphide-linked to the virion glycoprotein, gp70. FeLV p15(E) was sensitive to digestion of intact virus particles with the proteolytic enzyme, bromelain, indicating that this protein is on the outer surface of the virion. An analysis of cat sera for precipitating activity for FeLV p12(E) showed this only in sera from cats which had recovered from FeLV infection and had virus-neutralizing activity.

Animals↗
PubMed1980

Genetic variation and host markers in the src gene of recovered avian sarcoma viruses.

The src genes of three recovered avian sarcoma viruses were compared by RNase T1 oligonucleotide fingerprinting and tryptic peptide analysis. In all three recovered avian sarcoma viruses the oligonucleotide composition of src was different and also distinct from that of the parental Schmidt-Ruppin strain of Rous sarcoma virus. This evidence for genetic variation src was strengthened by two dimensional peptide maps of the src gene products pp60src, translated in a reticulocyte lysate system in vitro. Numerous differences between the peptide patterns of the pp60src proteins produced by the parental and the recovered viruses were detected. No two src proteins were identical, while the tryptic peptide maps of the internal gag proteins synthesized by these viruses were indistinguishable. The src proteins of recovered avian sarcoma viruses also contained peptides that were absent from the src protein of parental Schmidt-Ruppin D virus but were found in the endogenous src protein of normal cells. We conclude that there is considerable genetic variation in the src gene of recovered avian sarcoma viruses and that these recovered src genes contain host cell-derived markers.

Animals↗
PubMed1980

Feline calicivirus induced polypeptides.

Analysis of feline calicivirus-infected cell extract for large and low molecular weight proteins revealed the presence, in submolar amounts, of a polypeptide of molecular weight 80,000 daltons which had no precursor-product relationship to the capsid proteins (mol. wt 68,000 and 14,000) synthesized in infected cells. Two other highly labelled non-structural polypeptides of molecular weights 80,000 and 40,000 daltons yet to be identified were also described.

Animals↗
PubMedDate not supplied

Retroviral transduction of T-cell antigen receptor beta-chain and myc genes.

Support for multistage models of oncogenesis has been provided by several highly leukaemogenic retrovirus isolates that have transduced more than one host cell gene. Where functional studies have been performed, these retroviral oncogenes show synergy for in vitro transformation and leukaemogenesis. In naturally occurring feline leukaemias associated with feline leukaemia virus (FeLV), retroviral transduction of myc is a frequent oncogenic mechanism. But evidence suggesting that the FeLV v-myc genes might be insufficient for leukaemogenesis was provided by the latency (12 weeks) and clonality of FeLV/v-myc-induced tumours and the absence of demonstrable in vitro transformation by these viruses. In the search for secondary leukaemogenic events in FeLV/v-myc tumours, we have identified a case of FeLV transduction of a T-cell antigen receptor beta-chain gene. The proviruses carrying this gene (which we have named v-tcr) were a separate population from those carrying v-myc. In its normal role, the T-cell receptor beta-chain forms part of a multimeric complex involved in antigen recognition and T-cell activation. We suggest that v-tcr is a novel viral oncogene which assisted v-myc in the genesis of a naturally occurring case of thymic lymphosarcoma.

Animals↗
PubMedDate not supplied

Feline leukaemia viruses: molecular biology and pathogenesis.

The feline leukaemia virus (FeLV) group represents one of the most important viral pathogens of the domestic cat. In addition, this virus - host system is one of the major experimental models for retroviral pathogenesis. Under natural conditions, the virus is horizontally transmitted through the cat population. The outcome of infection depends on a variety of factors including the virus does encountered and the age and immune status of the host. FeLVs can establish persistent infection, either overt or latent. Degenerative diseases of the haemopoietic system are the most common result of persistent infection and immunosuppression with secondary infection accounts for more deaths than does neoplastic disease. However, more is known about the molecular mechanisms of oncogenesis in this system and there are now numerous examples of field case tumours where FeLV has transduced an oncogene or acted as an insertional mutagen. The factors affecting the relative frequency of these mechanisms are considered as is the possibility that recombinant env gene recombinants play a role in FeLV pathogenesis.

Animals↗