No abstract

The 28S RNA of the defective avian acute leukemia virus MC29 contains two sets of sequences: 60% are hybridized by DNA complementary to other avian tumor virus RNAs (group-specific cDNA) and 40% are hybridized only by MC29-specific cDNA. Specific and group-specific sequences of viral RNA, defined in terms of their large RNase TI-resistant oligonucleotides, were located on a map of all large T, oligonucleotides of viral RNA. Oligonucleotides representing MC2-specific sequences of viral RNAmnapped between 0.4 and 0.7 unit from the 3'-poly(A) end. Oligonucleotides of groupspecific sequences mapped between 0 and 0.4 and between 0.7 add I map unit. Cell-free translation of viral RNA yielded three proteins with approximate molecular weights of 120,000,356,000, and 37,000, termed P120me P5i, and P37mc. P120me contained both MC29specific peptiies and serological determinants and peptides of the conserved, internal group-specific antigens of avian tumor viruses. P120me is translated only from ful~length 28S RNA. Furthermore, MC29 RNA contains sequences related to the groupspecific antigen gene (gag), near the 5' end, which are folowed by MC29specific sequences. We conclude that this protein is translated from the 5' 60% of the RNA, and that it includes a segment translated from the specific sequences. It is suggested that the transforming (onc) gene of MC29 may consists of the specific and some group-specific RNA sequences and that Pl2rnc, which is also found in transformed cells, may be the onc gene product. MC29 is an avian RNA tumor virus that causes acute leukemia and carcinoma and also transforms fibroblasts in culture (1-4). The transforming or onc (5) gene of MC29 has not been defined genetically or biochemically. The viral genome is a 28S RNA (5700 nucleotides) that is identified as being MC29-specific by its absence from pure helper virus and because the sequence of 28S RNA is conserved when propagated with different helper viruses (6)(7)(8) However, if the specific sequences of MC29 are contiguous and if they code for a specific protein, they are candidates for a MC29 onc gene analogous to the src gene of RSV. Therefore we identified and located the MC29-specific sequences on the viral 28S RNA and then investigated the proteins encoded by these sequences. Preliminary work has been described recently (8). RESULTSMapping MC29-Specific and Group-Specific Sequences of MC29 RNA. Due to its defectiveness, MC29 virus can only be propagated in the presence of a helper virus. The helper virus used here was ring-neck pheasant virus (RPV) (4). The 50-70S RNA extracted from a mixture of MC29 and its helper contains two distinct monomer RNA species, a 34S helper virus RNA and a 28S MC29 RNA (6). The 28S MC29 RNA has been electrophoretically isolated and its RNase T1-resistant oligonucleotides have been analyzed by fingerprinting (Fig. 1A). The compositions, of the RNase A-resistant fragments of each oligonucleotide have been reported (6-8) and were extended and revised here as described in the legend of Fig. 1. To ...

The oncogenic properties and RNA of the Fujinami avian sarcoma virus (FSV) and the protein it encodes were investigated and compared to those of other avian tumor viruses with sarcomagenic properties such as Rous sarcoma virus and the acute leukemia viruses MC29 and erythroblastosis virus. Cloned stocks of FSV caused sarcomas in all chickens inoculated and were found to contain a 4.5-kilobase (kb) and an 8.5-kb RNA species. The 4.5-kb RNA was identified as the genome of defective FSV because it was absent from nondefective FSV-associated helper virus and because the titer of focusforming units increased with the ratio of 4.5-kb to 8.5-kb RNA in virus preparations. This is, then, the smallest known tumor virus RNA with a transforming function. Comparisons with other viral RNAs, based on oligonucleotide mapping and molecular hybridization, indicated that 4.5-kb FSV RNA contains a 5' gag gene-related sequence of 1 kb, an internal specific sequence of about 3 kb that is unrelated to Rous sarcoma virus, MC29, and erythroblastosis virus, and a 3'-terminal sequence of about 0.5 kb related to the conserved C region of avian tumor viruses. The lack of some or all nucleotide sequences of the essential virion genes, gag, pol, and env, and the isolation of FSV-transformed nonproducer cell clones indicated that FSV is replication defective. A 140,000-dalton, gag-related nonstructural protein was found in FSV-transformed producer and nonproducer cells and was translated in vitro from full-length FSV RNA. This protein is expected to have a transforming function both because its intracellular concentration showed a positive correlation with the percentage of transformed cells in a culture and because FSV is unlikely to code for major additional proteins since the genetic complexities of FSV RNA and the FSV protein are almost the same. It is concluded that the transforming onc gene of FSV is distinct from that of Rous sarcoma virus and other avian tumor viruses with sarcomagenic properties. Hence, multiple mechanisms exist for sarcomagenic transformation of avian cells.There are a number of sarcomagenic viruses in the avian tumor virus group that fall into discrete RNA subgroups, defined here on the basis of helper-virus unrelated, specific RNA sequences.[See below and ref. 1. Both defective and nondefective viruses can be classified consistently by using RNA subgroups (1). In contrast, only nondefective viruses can be classified on the basis of envelope subgroups (2). ] The Rous subgroup includes the replication-defective Bryan Rous sarcoma virus (RSV), the nondefective Schmidt-Ruppin strain, and the Prague strain of RSV (2, 3). The most common neoplasm produced by the RSV RNA subgroup of viruses is a sarcoma. The Rous subgroup is defined by a related class of transforming genes of 1.5 kilobases (kb) termed src (1, 4-7), which are located near the 3' end of viral RNA (6) and encode a 60-kilodalton nonstructural protein product thought to have a transforming function (8, 9). The ES4 strain of avian erythroblastosis virus...

No abstract