Nucleotide sequence of the 3' end of MCF 247 murine leukemia virus

We isolated DNA clones of MCF 247, a leukemogenic, recombinant type C virus obtained from the thymus of an AKR mouse. We determined the nucleotide sequence of the viral long terminal repeat (LTR) and the 3' end of env, and we compared the sequences to corresponding sequences of the genome of Akv virus, the putative ecotropic parent of MCF 247. By analogy with Moloney leukemia virus, we identified the amino terminus of Prp15E, the C-terminal proteolytic cleavage product of env and precursor to mature virion p15E. In MCF 247 the presumptive Prp15E is encoded by a 603-nucleotide open reading frame. The majority of this sequence is identical to that of Akv. However, a recombination event near the 3' end of the Prp15E-coding region introduces nonecotropic sequences into MCF 247, and these extend to the 3' end through the U3 portion of the LTR. The U3 regions of Akv and MCF 247 are about 83% homologous. The R and U5 regions of the LTR of MCF 247 and Akv are identical. Large RNase T1-resistant oligonucleotides analyzed previously in numerous ecotropic and MCF viral genomes were located within the Akv and MCF 247 DNA sequences. The resulting precise T1 oligonucleotide maps of the 3' ends of MCF viral genomes reveal that the biologically defined, leukemogenic class I MCFs isolated from thymic neoplasms of inbred mice all share the sequence pattern seen in MCF 247, a representative of this group; they possess recombinant Prp15E genes and derive U3 from their nonecotropic parents.     

At least four viral genes contribute to the leukemogenicity of murine retrovirus MCF 247 in AKR mice.

Nucleotide sequences encoding gp70, Prp15E, and the U3 region of the long terminal repeat (LTR) distinguish mink cell focus-forming (MCF) retroviruses that can induce leukemia in AKR mice from closely related MCF and ecotropic murine retroviruses that are nonleukemogenic in all inbred mouse strains tested (Lung et al., Cold Spring Harbor Symp. Quant. Biol. 44:1269-1274, 1979; Lung et al., J. Virol. 45:275-290, 1983). We used a set of recombinants constructed in vitro from molecular clones of leukemogenic MCF 247 and nonleukemogenic ecotropic Akv to separate and thereby directly test the role of these genetic elements in disease induction. Leukemogenicity tests of recombinants in AKR mice show that introduction of fragments containing either an MCF LTR or MCF gp70 coding sequences can confer only a very low incidence of disease induction on Akv virus, whereas an MCF type Prp15E alone is completely ineffective. Recombinants with an MCF 247 LTR in combination with MCF Prp15E are moderately oncogenic, whereas those with an MCF 247 LTR plus MCF gp70 coding segment are quite highly leukemogenic. Mice infected with the latter virus show a substantial increase in latent period of disease induction relative to MCF 247; this delay can be reduced when Prp15E, and hence the entire 3' half of the genome, is from MCF 247. Surprisingly, sequences in the 5' half of the genome can also contribute to disease induction. We found a good correlation between oncogenicity and recovery of MCF viruses from thymocytes of injected mice, with early recovery and high titers of MCF in the thymus being correlated with high oncogenicity. This correlation held for recombinants with either an MCF or ecotropic type gp70. Together, these results (i) demonstrate that at least four genes contribute to the oncogenicity of MCF viruses in AKR mice and (ii) suggest that recombinants with only some of the necessary MCF type genes induce leukemia because they recombine to generate complete MCF genomes. Although neither Akv nor MCF 247 is leukemogenic in NFS mice, recombinant viruses whose gp70 gene was derived from Akv but whose LTRs were derived from MCF 247 induced a low incidence of leukemia in this mouse strain.     

MCF-specific murine monoclonal antibodies made against AKR-247 MCF virus recognize a unique determinant associated with the gp70-p-15(E) complex.

Hybridomas obtained from (NFS X AKR)F mice immunized with syngeneic cells infected with AKR-247 MCF virus produced antibodies specific for only AKR-247 or closely related MCF viruses which hare a previously defined MCF antigen (MCFA-3). These monoclonal antibodies recognized a new type of viral antigenic determinant which appeared to be a conformational determinant associated with the env precursor polyprotein (pr80env) or its disulfide-linked gp70-p15(E) complex (gp80) but not with free gp70 or p15(E) or any other virion or virus-induced protein.     

Nucleotide sequence of the transforming gene of m1 murine sarcoma virus.

The v-mosm1 nucleotide sequence codes for a protein that is 376 amino acids long. Although the N-terminus is homologous with that of the v-mos124 protein, the C-terminus is substantially different from the C-termini of all other examined mos proteins, suggesting that this region is nonessential and perhaps cleaved. Overall, v-mosm1 has greater homology with c-mos than does v-mos124, but mutually exclusive differences between c-mos and each of the v-mos genes preclude linear descent and suggest a common ancestral murine sarcoma virus.     

Nucleotide sequence analysis of the BALB/c murine sarcoma virus transforming gene.

We determined the nucleotide sequence of the v-H-ras-related oncogene of BALB/c murine sarcoma virus. This oncogene contains an open reading frame of 189 amino acids that initiates and terminates entirely within the mouse cell-derived ras sequence. The protein encoded by this open reading frame matches the sequence predicted for the T24 human bladder carcinoma oncogene product, p21, in all but two positions. The presence of a lysine residue in position 12 of BALB/c murine sarcoma virus p21 likely accounts for its oncogenic properties.     

Nucleotide sequence of AKV murine leukemia virus.

AKV is an endogenous, ecotropic murine leukemia virus that serves as one of the parents of the recombinant; oncogenic mink cell focus-forming viruses that arise in preleukemic AKR mice. I report the 8,374-nucleotide-long sequence of AKV, as determined from the infectious molecular clone AKR-623. The 5'-leader sequence of AKV extends to nucleotide 639, after which lies a long open reading frame encoding the gag and pol gene products. The reading frame is interrupted by a single amber codon separating the gag and pol genes. The pol gene overlaps the env gene within the 3' region of the AKV genome. The nucleotide sequence of the 5' region of AKV reveals the following features. (i) The 5'-leader sequence lacks any AUG codon to initiate translation of gPr80gag, suggesting that gPr80gag is not required for the replication of AKV. (ii) A short portion of the leader region diverges in sequence from the closely related Moloney murine leukemia virus and appears to be related to a sequence highly repeated in eucaryotic genomes. (iii) As in Moloney murine leukemia virus, there is a potential RNA secondary structure flanking the amber codon that separates the gag and pol genes. This structure might function as a regulatory protein binding site that controls the relative levels of synthesis of the gag and pol precursors. The nucleotide sequence of the 3' region of AKV is compared with sequences reported previously from both infectious and noninfectious molecular clones of AKV.     

Serum gp70 production regulated by a gene on murine chromosome 7

We mated 129 mice (prototype strain of G_IX ⁺ with C5713L/6 mice (prototype strain of G_IX ^–) and thereby identified the gene controlling enhancement of serum gp70 production after lipopolysaccharide (LPS) injection. This gene has been tentatively designated Sgp-2. Sgp-2 is linked with the Hbb locus on chromosome 7. The estimated frequency of recombination between Sgp-2 and Hbb in this setting is about 20%.