Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The steady-state level and synthesis of a pair of polypeptides of Mr 33,000 and 35,000 in chicken embryo fibroblasts (CEF) transformed by Rous sarcoma virus (RSV) are significantly decreased relative to normal CEF; however, the decrease is more pronounced in the case of the Mr 35,000 polypeptide. These polypeptides have been identified as the alpha and beta subunits of CEF tropomyosin by selective staining with tropomyosin antibody, two-dimensional gel electrophoresis, partial peptide analysis, and solubility properties. The decrease in tropomyosin is shown to be a transformation-specific phenomenon in that it does not occur after infection with a virus deleted in src sequences. Decreased synthesis of tropomyosin is also observed in quail cells transformed by MC29 (a retrovirus with a different onc gene than that in RSV) and also in chemically transformed quail cells. The decreased in tropomyosin is probably not a direct result of the disruption of the microfilament system in transformed cells because disruption of the microfilament system with trypsin or cytochalasin B in normal CEF does not lead to a decrease in tropomyosin synthesis. A decrease in tropomyosin in CEF after transformation may be a result of a pleiotropic effect that results in the transcriptional inactivation not only of the tropomyosin gene but also of the fibronectin and procollagen genes described by others.
 ...
PMID:Tropomyosin is decreased in transformed cells. 627 10

We have identified a tyrosine kinase activity present in tumors which were raised in rats by subcutaneous injection of Rous sarcoma virus-transformed rat cells (SR-NRK). This kinase phosphorylates tyrosine on the heavy chain of IgG from tumor-bearing rabbit (TBR) sera specific for the src gene product, pp60src. Using TBR-IgG phosphorylation as an assay, we have purified this kinase over 7200-fold. The purification procedure involves detergent extraction of tumors followed by sequential column chromatography on hydroxylapatite, DEAE-Sephacel, oligodeoxyadenosine-cellulose, an affinity column prepared from TBR-sera, and Sephacryl S-200. The IgG kinase activity behaves as a molecule of apparent Mr = 54,000 on Sephacryl S-200 molecular sieve chromatography. Analysis of the Sephacryl fractions by SDS-PAGE indicates that a major Coomassie blue-stained band with an apparent Mr = 54,000 (p54), co-elutes with the peak of kinase activity. From 600 g of tumors, approximately 200 micrograms of p54 are obtained. We have four types of evidence which show that p54 is related to pp60src. 1) Purified p54 is capable of undergoing endogenous phosphorylation in the presence of [gamma-32P]ATP producing a 32P-labeled pp54 polypeptide which is specifically immunoprecipitated by TBR-sera and contains only phosphotyrosine. 2) Purified p54 competes with 32P-labeled pp60src for binding to TBR-IgG, indicating a degree of purification over starting material which agrees very well with the results obtained by the IgG kinase assay. 3) V8 protease digestion of pp60src and p54 suggests that they share a common 26,000 fragment. 4) Antibodies to partially purified p54 specifically precipitate pp60src from Rous sarcoma virus-transformed chicken cells.
 ...
PMID:Purification of a tyrosine-specific protein kinase from Rous sarcoma virus-induced rat tumor. 628 32

A Marek's disease lymphoblastoid cell line (MSB-1) has been analysed by immunoprecipitation for expression of tumour-associated antigen, Marek's disease virus (MDV)-specific antigens and antigens specific to avian leukosis-sarcoma viruses. Rabbit antisera raised against two independently derived cell lines after extensive absorption with normal chick cells reacted with a polypeptide of mol. wt. 40 000 (40K) in extracts of MSB-1 cells. The 40K polypeptide was not present in myeloblasts or in chick embryo fibroblasts (CEF) infected with MDV and did not react with antiserum raised against normal chicken thymus antigens. The possibility that the 40K polypeptide is a tumour-associated antigen is discussed. Seven MDV-specific antigens were noted in infected CEF (mol. wt. 110K, 100K, 80K, 70K, 50K, 35K and 32K) but none of these was detected in MSB-1 cells. The avian leukosis-sarcoma group-specific antigen P27gag and its precursor Pr76gag were not found in MSB-1 cells, confirming that expression of mature gag protein is not required for transformation by MDV. However, two polypeptides of unknown origin and function (mol. wt. 180K and 110K) were precipitated from MSB-1 cells with a rabbit anti-Rous sarcoma (Schmidt-Rupin, subgroup D) antiserum.
 ...
PMID:Characterization of an antigen associated with the Marek's disease lymphoblastoid cell line MSB-1. 628 57

We have examined the phosphorylation of a 50,000-dalton cellular polypeptide associated with the Rous sarcoma virus (FSV) transforming protein pp60-src. It has been shown that pp60src forms a complex with two cellular polypeptides, an 89,000-dalton heat-shock protein (89K) and a 50,000-dalton phosphoprotein (50K). The pp60src-associated protein kinase activity phosphorylates at tyrosine residues, and the 50K polypeptide present in the complex contains phosphotyrosine and phosphoserine. These observations suggest that the 50K polypeptide may be a substrate for the protein kinase activity of pp60src. To examine this possibility, we isolated the 50K polypeptide by two-dimensional polyacrylamide gel electrophoresis from lysates of uninfected or virally infected cells. Tryptic phosphopeptide analysis indicated that the 50K polypeptide isolated by this method was the same polypeptide as that complexed to pp60src. In uninfected cells or cells infected by a transformation-defective mutant, the 50K polypeptide contained phosphoserine but little or no phosphotyrosine. In cells infected by Schmidt-Ruppin or Prague RSV, there was a 40- to 50-fold increase in the quantity of phosphotyrosine in the 50K protein. Thus, the phosphorylation of the 50K polypeptide at tyrosine is dependent on the presence of pp60src. However, the 50K polypeptide isolated from cells infected by temperature-sensitive mutants of RSV was found to be phosphorylated at tyrosine at both permissive and nonpermissive temperatures; this behavior is different from that of other substrates or putative substrates of the pp60src kinase activity. It is possible that the 50K polypeptide is a high-affinity substrate of pp60src.
 ...
PMID:Tyrosine phosphorylation of a 50K cellular polypeptide associated with the Rous sarcoma virus transforming protein pp60src. 628 29

The half-life of metabolically labeled pp60src of the Prague A strain of Rous sarcoma virus and of several transformation-defective, temperature-sensitive mutants was investigated by pulse-labeling infected cells with [35S]methionine, chasing for different times, and immunoprecipitating pp60src with tumor-bearing rabbit serum. These experiments showed that pp60src has a short half-life of approximately 60 min under normal physiological conditions and that the mutant pp60src proteins have similar half-lives to the wild type, irrespective of whether the cells are kept at the nonpermissive (42 degrees C) or permissive (35 degrees C) temperature. The half-life of the pp60src -associated kinase activity was determined by monitoring its decay by the immunoglobulin G heavy chain assay after the cells had been treated with several inhibitors of protein synthesis. In these experiments the kinase half-life was much longer than expected from the half-life of pp60src. The apparent contradiction between the half-lives of the kinase activity and the [35S]methionine-labeled pp60src protein could be resolved by the observation that treatment of cells with inhibitors of protein synthesis stabilized pp60src, resulting in a greatly extended half-life. Inhibitors of protein synthesis also extended the half-life of the gag precursor polypeptide, Pr76, suggesting that a host factor(s) may be required for the efficient intracellular processing of this polypeptide to the gag proteins.
 ...
PMID:Half-life of the Rous sarcoma virus transforming protein pp60src and its associated kinase activity. 628 35

Plasma membrane-associated polypeptides of chick embryo fibroblasts and cells transformed by the Schmidt-Ruppin wild-type strain of Rous sarcoma virus and its temperature-sensitive tsNY68 mutant were compared by two-dimensional gel electrophoresis. Polypeptide and glycoprotein alterations were identified after incubation of cells with [35S]methionine and [3H]mannose and by staining of the gels with 125I-labeled concanavalin A and Coomassie brilliant blue. Polypeptides found to be consistently transformation-sensitive included a group of five polypeptides that were detected only by short-term labeling with methionine, fibronectin, a 180 kDa polypeptide with a pI of 5.6, a mannose-containing glycoprotein of 48 kDA and an unusually high pI of 8.4, and a 19 kDa polypeptide with a pI of approx. 4.5. Several of these polypeptides appear to be particularly interesting for further characterization.
 ...
PMID:A survey of differences between membrane polypeptides of transformed and nontransformed chick embryo fibroblasts. 629 80

We have found that the transforming proteins of Rous sarcoma virus, Harvey sarcoma virus and Abelson virus all contain tightly bound lipid. This modification could play a role in the binding of these proteins to cellular membranes. The lipid associated with p60src, the transforming protein of Rous sarcoma virus, is located in the NH2-terminal domain of the polypeptide. This is the region of the protein that has been shown previously to participate in binding the protein to membranes. Two mature forms of p21, the transforming protein of Harvey sarcoma virus, contain lipid. Lipid is not, however, associated with newly synthesized p21. While mature p60src and p21 are bound to cellular membranes, the newly synthesized forms of these proteins are not. The posttranslational addition of lipid may therefore be the means by which these proteins acquire an affinity for membranes.
 ...
PMID:The transforming proteins of Rous sarcoma virus, Harvey sarcoma virus and Abelson virus contain tightly bound lipid. 629 67

The Y73 strain of avian sarcoma virus isolated from a transplantable chicken tumor was defective in its replicating capacity. The virus caused sarcoma but not acute leukosis in chickens even when inoculated intravenously. It induced transformed cell-foci in cultured fibroblasts and the viral genome responsible for in vitro transformation was 26S RNA. The RNA was composed of sequences in common with helper virus RNA and Y73-specific sequence. The specific sequence "yes" did not hybridize with complementary DNA to the src gene of Rous sarcoma virus (cDNAsrc) and it had a unique counterpart in normal cell DNA. The yes gene was located in the middle of the 26S genome and the sequences common to the helper virus were located toward both ends. The 26S RNA coded for an polyprotein of 90,000 daltons (p90) which included p19 of viral core proteins in addition to the polypeptide unique to the yes gene. p90 had protein kinase activity specific for tyrosine residue and itself could be phosphorylated at tyrosine residue in vivo and in vitro, and at serine residue in vivo.
 ...
PMID:Oncogene and its production of an avian sarcoma virus Y73. 630 25

The mechanism of SV40-induced cellular transformation was investigated by two-dimensional gel analysis of 35S- and 32P-labeled proteins of various cells. These included rat and mouse cells, either transformed or abortively infected by SV40 wild type, small t deletion mutants, and a large T temperature-sensitive mutant. Synthesis, turnover, or (de)phosphorylation of multiple protein spots was found to be reproducibly and quantitatively influenced by the transformed and/or infected status. Several of these alterations were attributable to the biological activity of either large T or small t antigen. Most changes in 35S-labeled proteins corresponded to a decreased intensity of the gel spots in transformed cells, while hyperphosphorylated proteins were more common than hypophosphorylated ones. About half of the polypeptide alterations in 35S-and 32P-labeled SV40-transformed rat cells, including a set of 35S-labeled small t-dependent changes were shared by Rous sarcoma virus-transformed cells. In contrast, small t-dependent (de)phosphorylation was rarely detected. Phosphoamino acid analysis of selected phosphoprotein spots of rat cells and alkaline hydrolysis of whole two-dimensional gels did not reveal any evidence for increased tyrosine-specific phosphorylation after SV40-induced transformation. Abortively infected mouse cells showed many protein alterations, also observed in stably transformed cells. However, the latter cells contained additional changes, also affecting several phosphoproteins and possibly related to the establishment of transformation. These findings are discussed in relation to the biological functions, known or presumed, for SV40 large T and small t antigens during transformation.
 ...
PMID:Changes in gene expression and protein phosphorylation in murine cells, transformed or abortively infected with wild type and mutant simian virus 40. 630 Jan 25

We have identified p10 as a fifth gag protein of avian sarcoma and leukemia viruses. Amino-terminal protein sequencing of this polypeptide purified from the Prague C strain of Rous sarcoma virus and from avian myeloblastosis virus implies that it is encoded within a stretch of 64 amino acid residues between p19 and p27 on the gag precursor polypeptide. For p10 from the Prague C strain of Rous sarcoma virus the first 30 residues were found to be identical with the predicted amino acid sequence from the Prague C strain of Rous sarcoma virus DNA sequence, whereas for p10 from avian myeloblastosis virus the protein sequence for the same region showed two amino acid substitutions. Amino acid composition data indicate that there are no gross composition changes beyond the region sequenced. The amino terminus of p10 is located two amino acid residues past the carboxy terminus of p19, whereas its carboxy terminus probably is located immediately adjacent to the first amino acid residue of p27.
 ...
PMID:Amino-terminal amino acid sequence of p10, the fifth major gag polypeptide of avian sarcoma and leukemia viruses. 630 Apr 42


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>