Addition of substitution of simian virus 40 enhancer sequences into the Moloney murine leukemia virus (M-MuLV) long terminal repeat yields infectious M-MuLV with altered biological properties.
Moloney murine leukemia virus (M-MuLV) is a replication-competent retrovirus which induces T-cell lymphoma in mice. The enhancer sequences present within the M-MuLV long terminal repeat (LTR) region of the proviral genome have been shown to influence the disease specificity of the virus strongly. We examined the contribution of the M-MuLV enhancers to the transcriptional activity and pathogenesis of M-MuLV by constructing LTRs containing heterologous enhancer elements. The simian virus 40 enhancer region (72- and 21-base-pair repeats) was inserted into the U3 region (at -150 base pairs) of the M-MuLV LTR (Mo + SV) and also into a deleted form of the LTR which lacks the M-MuLV enhancer sequences (delta Mo + SV). These chimeric LTRs were used to generate infectious M-MuLVs by transfection of corresponding proviral plasmids into mouse fibroblasts. The relative infectivities of Mo + SV and delta Mo + SV recombinant viruses as determined by rat XC cell plaque assay and reverse transcriptase assay were 60 to 70% of wild-type M-MuLV levels. To study the pathogenicity of these two recombinant viruses, we inoculated newborn NIH Swiss mice with either Mo + SV or delta Mo + SV M-MuLV. Both viruses induced disease more slowly than M-MuLV, which induces disease 2 to 4 months postinoculation. Mo + SV M-MuLV-inoculated animals became moribund at 3 to 13 months postinoculation, whereas delta Mo + SV M-MuLV-inoculated animals became moribund at 6 to 24 months postinoculation. The tumors induced by the two viruses were characterized histologically and molecularly. Mo + SV M-MuLV-induced tumors were primarily T-cell-derived lymphoblastic lymphomas containing extensive rearrangements of the T-cell receptor beta gene. In contrast, delta Mo + SV M-MuLV induced pre-B- and B-cell lymphoblastic lymphomas, B-cell-derived follicular-center cell lymphomas, and acute myeloid leukemia. The delta Mo + SV tumor DNAs from B-lineage tumors were typically rearranged at the immunoglobulin gene loci and contained germ line configurations of the T-cell receptor beta gene. Southern blot hybridization confirmed that the tumor DNAs contained the predicted Mo + SV M-MuLV or delta Mo + SV M-MuLV provirus.
Hanecak
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R
Department of Molecular Biology and Biochemistry, University of California, Irvine 92717.
Pattengale
P K
PK
Fan
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H
D000818:Animals; D001402:B-Lymphocytes / Q000473:pathology; D004273:DNA, Neoplasm / Q000032:analysis; D004279:DNA, Viral / Q000032:analysis; D004742:Enhancer Elements, Genetic; D005814:Genes, Viral; D015470:Leukemia, Myeloid, Acute / Q000209:etiology / Q000235:genetics / Q000473:pathology; D008228:Lymphoma, Non-Hodgkin / Q000209:etiology / Q000235:genetics / Q000473:pathology; D051379:Mice; D008979:Moloney murine leukemia virus / Q000235:genetics* / Q000472:pathogenicity; D011519:Proto-Oncogenes; D011533:Proviruses / Q000032:analysis; D012091:Repetitive Sequences, Nucleic Acid; D013539:Simian virus 40 / Q000235:genetics*; D013601:T-Lymphocytes / Q000473:pathology; D013997:Time Factors
D004273:DNA, Neoplasm; D004279:DNA, Viral