Influence of phosphate on activity and stability of reverse transcriptase from avian myeloblastosis virus

Two protein kinase activities were fractionated from purified virions of avian myeloblastosis virus. Distinguishing characteristics of these two protein kinases included: (i) their binding properties during purification by ion-exchange chromatography; (ii) their estimated molecular weights; and (iii) their phosphoacceptor protein specificities. The protein kinase that bound to the anion exchanger DEAE-cellulose (pH 7.2) had an estimated molecular weight of 60,000 to 64,000 and preferred basic phosphoacceptor proteins. The protein kinase that bound to the cation exchanger phosphocellulose (pH 7.2) had an estimated molecular weight of 42,000 to 46,000 and preferred acidic phosphoacceptor proteins. The protein kinase preferring basic phosphoacceptor proteins was further purified and characterized. Optimal transfer of phosphate catalyzed by this enzyme required a divalent metal ion, a sulfhydryl-reducing agent, and ATP as phosphate donor. GTP was not an effective phosphate donor at concentrations comparable to ATP; and the cyclic nucleotides cyclic AMP and cyclic GMP neither stimulated nor inhibited protein phosphorylation by the protein kinase. The specificity of the protein kinase for basic phosphoacceptor proteins extended to proteins from avian myeloblastosis virus, in that the neutral to basic virion proteins p12, p19, and p27 served as phosphate acceptors. In addition, the protein kinase also appeared to phosphorylate itself. The role(s) of this virion-associated protein kinase is discussed.

“…VOL 29,. 1979 Downloaded from https://journals.asm.org/journal/jvi on 30 August 2021 by 44.224.250.200.…”

mentioning

confidence: 99%

Fractionation of two protein kinases from avian myeloblastosis virus and characterization of the protein kinase activity preferring basic phosphoacceptor proteins

Rosok¹,

Watson²

1979

“…The virion-associated kinase responsible for phosphorylation of IN and 1 has not been identified, although several kinases have been purified from RSV and avian myeloblastosis virus (AMV) (14,20). It is unclear whether phosphorylation directly affects the enzymatic properties of IN or RT (11,18,19).…”

mentioning

confidence: 99%

v-Src enhances phosphorylation at Ser-282 of the Rous sarcoma virus integrase

Mumm

Horton

Grandgenett

1992

The Rous sarcoma virus (RSV) integrase (IN) and the 13 polypeptide (13) of the reverse transcriptase are posttranslationally modified by phosphorylation on Ser at amino acid position 282 of IN. When IN was immunoprecipitated from RSV (Prague A strain) virions, approximately 30 to 40%o of the IN molecules were phosphorylated. When IN was immunoprecipitated from a v-src deletion mutant (AMst-A) of RSV or from avian myeloblastosis virus (AMV), the percentage of IN molecules that were phosphorylated was significantly reduced. This reduction in phosphorylation of IN between virions was verified by [35SJMet-[35SJCys or 32p labeling of IN, followed by immunoprecipitation analysis using antisera directed to the amino or carboxyl terminus of IN. In AMst-A or AMV, a nonphosphorylated, slightly truncated (at the carboxyl terminus) polypeptide was the major species of IN. The enhanced phosphorylation of IN does not appear to be a general function of transformed cells, since enhanced phosphorylation was not detected in AMV derived from viremic chickens or from a v-src deletion mutant of RSV propagated in a chemically transformed quail cell line, QT6. From these data, we conclude that v-Src is necessary for efficient phosphorylation of IN and 13.

“…, and 70 U of avian myeloblastosis virus polymerase(42) in a final volume of 250 pl. For [3H]cDNA, 1 mCi of [3H]dTTP (55 Ci/mmol; Schwarz/Mann, Orangeburg, N.Y.) was added to the reaction mixture to give a fmal dTTP concentration of about 7 x 10-2 mM.…”

mentioning

confidence: 99%

Identification of nucleotide sequences which may encode the oncogenic capacity of avian retrovirus MC29

Sheiness¹,

Fanshier²,

Bishop³

1978

136

The retrovirus strain MC29 induces a variety of tumors in chickens, including myelocytomatosis and carcinomas of the kidney and liver. In addition, the virus can transform cultures of embryonic avian macrophages and fibroblasts. We have characterized the genome of MC29 virus and have identified nucleotide sequences that may encode the oncogenic potential of the virus. MC29 virus can replicate only with the assistance of a related helper virus. The defect in replication is apparently a consequence of a deletion in one or more viral genes: the haploid genome of the MC29 virus has a molecular weight of ca. 1.7 x 106, whereas the genome of the helper virus MCAV has a molecular weight of ca. 3.1 x 106. Although MC29 virus transforms fibroblasts in culture, its genome has no detectable homology with the gene src that is responsible for transformation of fibroblasts by avian sarcoma viruses. We prepared radioactive single-stranded DNA complementary to nucleotide sequences present in the genome of MC29 virus but not in the genome of MCAV (cDNAMc29). If they are contiguous, these sequences (ca. 1,500 nucleotides) are sufficiently complex to encode at least one protein. Homologous sequences were not detectable in several strains of avian sarcoma viruses or in an endogenous virus of chickens. Our findings confirm and extend recent reports from other laboratories and lead to the conclusion that MC29 virus may contain a previously unidentified gene(s) that is capable of transforming several distinct target cells. The evolutionary origins of this putative gene and its location on the viral genome can be explored with cDNAMC29.