Rous associated virus

Rous-associated virus-7 (RAV-7) was the second pathogen reported to cause obesity. In addition, it causes stunting and hyperhpidemia in chickens (Carter et al., 1983a). The following is a description of the adipogenic effects of RAV-7. 

an avian leukosis virus (Carter and Smith, 1984), has an 8.2-kb RNA (Carter et al., 1983a). It is the most common naturally occurring avian retrovirus associated with neoplastic disease condition in domesticated poultry (Fadly, 1997). 

Avian retroviruses have also been classified into two groups based on the time required to produce tumors (Graf and Beug, 1978). However between these groups, there is another group that produces tumors like osteopetrosis after an intermediate latency time (Smith and Moscovici, 1969), immunosuppression (Smith and Van Eldik, 1978), stunting (Banes and Smith, 1977), and anemia (Paterson and Smith, 1978 Smith and Schmidt, 1982). Carter 

Carter et al. (1983a) showed that RAV-7 induces obesity in chickens, which is characterized by stunting and hyperlipidemia. Birds, when infected as 10-day-old embryos, developed fat deposition around crop and abdominal fat pads. Whereas inoculation of 1-day-old hatched chickens did not produce stunting or obesity (Carter et al., 1983a). Difference in food intake was observed only after 3 weeks, when stunting and obesity developed (Carter et al., 1983b). 

Carter et al. (1983a,b) reported that the obesity-promoting effects of RAV-7 are common for the subgroup C of avian leucosis viruses, but not for the other subgroups (A, B, D, or F). Chickens infected with subgroups A, B, D, E, and F showed osteopetrosis (predominant for MAV-1 and MAV-2), anemia, liver lesions, blood cysts, fibrosarcoma, or nephroblastoma (predominant for MAV-2), but did not develop adiposity (Carter and Smith, 1984). 

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Selected naturally occurring flavonoids have been shown to inhibit three reverse transcriptases (RT) (avian myeloblastosis RT, Rous-associated virus-2 RT, and Moloney murine leukemia virus, or MMLV, RT) when poly(rA)oligo(dT) 12-18 or rabbit globin mRNA was used as a template. Amentoflavone, scutellarein, and quercetin were the most active compounds, and their effect was concentration dependent. The enzymes exhibited differential sensitivity to the inhibitory effects of the flavonoids. These flavonoids also inhibited rabbit globin mRNA-directed MMLV RT-catalyzed... 

DNA synthesis. Amentoflavone and scutellarein inhibited ongoing new DNA synthesis catalyzed by Rous-associated virus-2 RT. 

Felder, M.P. Eychene, A. Barnier, J.V. Calogeraki, I. Calothy, G. Marx, M. Common mechanism of retrovirus activation and transduction of c-mil and c-Rmil in chicken neuroretina cells infected with Rous-associated virus type 1. J. Virol., 65, 3633-3640 (1991)... 

C. Mechanisms of CDV-Induced Obesity Rous-Associated Virus-7... 

Defective viruses viruses that lack genes for the synthesis of functional capsid or envelope proteins. For example, the Rous sarcoma virus is unable to synthesize one of its envelope proteins. In order to complete its replication cycle and form new virus particles, the missing gene must be provided by a helper virus. The helper virus is a member of a group of viruses often found in association with the Rous sarcoma virus, and known as Rous-associated viruses (RAV). In the absence of an RAV, the normal host cell is transformed into a tumor-forming cell. Most acute transforming Retroviridae are D.v. Deficient viruses (see) are often included with the D.v. 

Sarcoma viruses. This group includes avian sarcoma virus (ASV), Rous-associated virus and other fowl sarcoma viruses murine sarcoma virus (MSV) (28, 265, 454) feline sarcoma virus (FeSV) (298) and sarcoma viruses of primates, including woolly monkey (SSV) (516) and gibbon ape (GaSV). 

This enzyme is associated with the virions of RNA tumor viruses such as the Rous sarcoma virus (RSV). The enzyme has remarkable enzymatic activity in that it can catalyze several seemingly diverse steps in the synthesis of double-stranded DNA from the single-stranded RNA viral genome. The enzyme uses a tRNA for tryp-tophan as a primer to make a copy of DNA that is complementary to the viral RNA. The resulting RNA-DNA hybrid is converted to a double-stranded DNA molecule by ribon-uclease (RNase)H and DNA-dependent DNA polymerase activities that are intrinsic to reverse transcriptase. 

Certain RNA viruses, particularly retroviruses, have also proven capable of inducing cancer. Retroviruses known to induce cancer in animals include Rous sarcoma virus, Kirsten murine sarcoma virus, avian myelocytomatosis virus, as well as various murine leukaemia viruses. Thus far, the only well-characterized human RNA transforming virus is that of human T cell lymphocytotropic virus-1 (HTLV-1), which can induce adult T cell leukaemia/lymphoma (ATL). Identification of antigens uniquely associated with various tumour types, and identification of additional cancer-causing viruses, remain areas of very active research. 

Src is a oncogene first found in the Rous sarcoma virus where it encodes the pp60 kinase. The corresponding cellular kinase is pp60 -s =. The Src kinases are regulated by phosphorylation de-phosphorylation. Members of the Src family of cytosolic tyrosine kinases with important funtions in cell signalling are for example Yes, Fyn, Lck, Blk, Btk, Csk, Hck, Fgr and Yrk. Fyn associates with the p85 subunit of 1-phosphatidyl inositol... 

Most of oncogene products that are protein kinases phosphorylate specific tyrosine residues. Examples of these are src, fps, yes and sea. RSVsrc, which occurs in Rous sarcoma virus, has been the most studied. The gene products of src, fps and yes are peripheral membrane proteins associated with the cytoplasmic surface of the plasmalemma (Fig. 11.5). Both p60 " and p60 possess specific tyrosine kinase activity but with an important functional difference, namely, that p60 " kinase activity is regulated through normal cellular mechanisms and does not transform cells, whereas kinase is readily activated and... 

Compared with normal chondrocytes the accumulation of extracellular glycosaminoglycans in the cell layer of Rous sarcoma virus-transformed chondrocytes is reduced. Virtually all of the secreted glycosaminoglycan of the transformed cells, most of which is hyaluronic acid, is deposited in a cell surface-associated compartment and then rapidly shed into the medium. 

Src homology domains, SH domains conserved -100-residue domains first recognized in tyrosine kinases related to Src protein (an oncogene product of Rous sarcoma virus). Many non-receptor tyrosine kinases that are activated by tyrosine l ase-associated receptors are members of the Src family. These -500-residue, membrane anchored (by myristoylation) proteins contain at least one SH domain (SH2), and some possess a second SH domain known as SH3. Certain membrane-associated proteins possess only the SH3 domain. 

Thus, the antiviral activity of the thiosemicarbazones has been correlated, in one study, with their ability to inhibit ribonucleotide reductase [8]. Methisazone inhibits the RNA-dependent DNA polymerase of Rous sarcoma virus (RSV) and inactivates its ability to transform chick-embryo cells [9], as well as inactivating herpes simplex [10] and some RNA viruses [11]. The activity against RSV is Cu-dependent [9], the Cu complex also being capable of inhibition of the polymerase [12]. Since these enzymes are zinc-dependent, interference with the role of zinc is possible. The inhibition of influenza virus-associated RNA transcriptase by... 

The association of viruses and cancer was demonstrated by Peyton Rous in 1911, when he used ceU-free extracts from a tumor extracted from a Plymouth Rock chicken to induce tumors in healthy chickens. Fifty-five years later, four years before his death at the age of ninety, Rous was awarded a Nobel Prize. 

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