RESUMO
The BL/VL(3) Kaplan radiation leukemia virus (RadLV-VL(3)) is a nondefective retrovirus that induces T cell lymphomas in several strains of mice. By using DNA probes derived from RadLV/VL(3) provirus-flanking sequences cloned from the BL/VL(3) cell line, we identified a DNA region rearranged in 5 of 19 tumors analysed (25%). All proviruses were integrated in the same 5'-to-3' orientation in a small DNA region called Kis1 (Kaplan integration site 1). This region was localized on distal mouse chromosome 2 in a region not previously identified as important to lymphomagenesis. The cells rearranged at the Kis1 locus represent a clonal subpopulation of the clonal tumor masses examined, indicating a probable role of Kis1 in tumor progression.
Assuntos
Mapeamento Cromossômico , Linfoma de Células T/genética , Linfoma de Células T/virologia , Provírus/genética , Vírus da Leucemia Induzida por Radiação/genética , Integração Viral , Animais , Cruzamentos Genéticos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Muridae , Mapeamento por Restrição , Infecções por Retroviridae/genética , Infecções por Retroviridae/virologia , Linfócitos T/virologia , Células Tumorais Cultivadas , Infecções Tumorais por Vírus/genética , Infecções Tumorais por Vírus/virologiaRESUMO
We report the complete nucleotide sequence of the genome of Rauscher murine leukemia virus (R-MuLV), the replication-competent helper virus present in the Rauscher virus complex, and its phylogenetic relationship with other murine leukemia virus genomes. An overall sequence identity of 97.6% was found between R-MuLV and the Friend helper virus (F-MuLV), and the two viruses were closely related on the phylogenetic trees constructed from either gag, pol, or env sequences. Moloney murine leukemia virus (Mo-MuLV) was the next closest relative to R-MuLV and F-MuLV on all trees, followed by Akv and radiation leukemia virus (RadLV). The most distantly related helper virus was Hortulanus murine leukemia virus (Ho-MuLV). Interestingly, Cas-Br-E branched with Mo-MuLV on the gag and pol trees, whereas on the env tree, it revealed the highest degree of relatedness to Ho-MuLV, possibly due to an ancient recombination with an Ho-MuLV ancestor. In summary, a phylogenetic analysis involving various MuLVs has been performed, in which the postulated close relationship between R-MuLV and F-MuLV has been confirmed, consistent with the pathobiology of the two viruses.
Assuntos
Genoma Viral , Vírus da Leucemia Murina/genética , Filogenia , Vírus Rauscher/genética , Algoritmos , Animais , Vírus da Leucemia Murina de Friend/classificação , Vírus da Leucemia Murina de Friend/genética , Vírus da Leucemia Murina/classificação , Camundongos , Dados de Sequência Molecular , Vírus da Leucemia Murina de Moloney/classificação , Vírus da Leucemia Murina de Moloney/genética , Vírus da Leucemia Induzida por Radiação/classificação , Vírus da Leucemia Induzida por Radiação/genética , Vírus Rauscher/classificaçãoRESUMO
The mechanism by which non-oncogene-bearing, slowly transforming retroviruses induce leukemia is not well understood, but appears to represent a multi-step process. Cell lines have been isolated following in vitro infection of lymphoid cells with radiation leukemia virus (RadLV) and they have been used to develop a two-step model for leukemia development. Thymic tumors were induced when one of the cell lines, C1-V13D, was inoculated into CBA/H mouse thymus. Upon reisolation of C1-V13D cells after one, two and three passages through thymus, individual cloned cell lines displayed increased tumorigenic potential compared with the non-tumorigenic parental line. Southern analysis has been used to track any genetic changes occurring while cells undergo further transformation and become increasingly tumorigenic. Specifically, retrovirus integration has been monitored in clones derived from C1-V13D at the primary, secondary and tertiary passage through thymus using probes specific for long terminal repeat (LTR), gag, pol and env genes of RadLV. The data indicate multiple ecotropic retrovirus integration sites in C1-V13D cells. Primary thymic tumors also showed the integration of a new recombinant or defective virus. There was no evidence that new ecotropic retrovirus integration had occurred during subsequent passage of primary tumors through the thymus, i.e. during the progression to oncogenesis. All data indicate an important role for the thymic environment in the development of a fully transformed cell.
Assuntos
Transformação Celular Viral/efeitos da radiação , Leucemia Experimental/genética , Leucemia Experimental/microbiologia , Oncogenes/efeitos da radiação , Vírus da Leucemia Induzida por Radiação/genética , Animais , Divisão Celular/fisiologia , DNA Viral/genética , Modelos Animais de Doenças , Feminino , Masculino , Camundongos , Camundongos Endogâmicos CBA , Timo/citologia , Timo/microbiologia , Neoplasias do Timo/microbiologia , Neoplasias do Timo/patologia , Integração ViralRESUMO
BL/VL3 radiation leukemia virus (RadLV) is a thymotropic, highly leukemogenic murine leukemia virus (MuLV) which is unable to replicate in vitro in mouse fibroblasts. We have previously reported that the U3 long terminal repeat region of its genome is responsible for this block (E. Rassart, Y. Paquette, and P. Jolicoeur, J. Virol. 62:3840-3848, 1988). By using hybrids of permissive and resistant cells infected with BL/VL3 RadLV or fibrotropic MuLV, we found that the resistant phenotype was dominant. Investigation to determine at which step of the virus cycle the block operates revealed that integration, transcription, and translation of the BL/VL3 viral genome occurred at normal levels in nonpermissive cells. The BL/VL3 RadLV Pr65gag proteins made in nonpermissive cells were also myristylated and located at the membrane, and the levels of their cleaved products were similar to those of fibrotropic MuLV. However, processing of BL/VL3 RadLV Pr85env was impaired in nonpermissive cells. Virions were not released into the culture medium of nonpermissive cells, as measured by reverse transcriptase activity and by content in p30 or gp70 protein and as documented by lower levels of budding particles seen by electron microscopy. These results indicate that BL/VL3 RadLV replication is blocked at a late stage of the virus cycle, i.e., at virion assembly. Interestingly, these BL/VL3 RadLV-infected nonpermissive fibroblasts were resistant to superinfection by fibrotropic Moloney MuLV, and this resistance also occurred at a late step of the Moloney virus cycle. Since this block is dominant, it appears that the U3 long terminal repeat region of the BL/VL3 viral genome has the ability to induce a cellular suppressor factor(s), thus bringing intracellular immunity against itself and against other ecotropic MuLVs.
Assuntos
Imunidade Celular , Vírus da Leucemia Induzida por Radiação/genética , Vírus da Leucemia Induzida por Radiação/imunologia , Sequências Repetitivas de Ácido Nucleico , Retroviridae/genética , Retroviridae/imunologia , Animais , Linhagem Celular , Cloranfenicol O-Acetiltransferase/genética , Cloranfenicol O-Acetiltransferase/metabolismo , Células Clonais , DNA/análise , DNA/genética , DNA Viral/análise , DNA Viral/biossíntese , DNA Viral/genética , Produtos do Gene gag/genética , Produtos do Gene gag/isolamento & purificação , Produtos do Gene gag/metabolismo , Camundongos , Ácido Mirístico , Ácidos Mirísticos/metabolismo , Plasmídeos , Processamento de Proteína Pós-Traducional , Provírus/genética , Provírus/imunologia , Linfócitos T , Transfecção , Integração ViralRESUMO
Radiation leukemia viruses (RadLVs) are a group of murine leukemia viruses which are induced by radiation and cause T-cell leukemia. Viral clones isolated from the BL/VL3 lymphoid cell line derived from a thymoma show variable tropism and leukemogenic potential. We have constructed chimeric viruses by in vitro recombination between two viruses, a RadLV that is thymotropic and an endogenous ecotropic virus that is nonthymotropic. We show here that, in contrast to thymotropism determinants identified previously, which lie in the long terminal repeat (LTR), it is the envelope region that is responsible for the thymotropism of BL/VL3 RadLV. The nonthymotropic virus which we have rendered thymotropic by transfer of the env region of RadLV in the present study has been shown previously to become thymotropic when the LTR of another thymotropic virus is inserted in its genome. Thus, the LTR and envelope gene may be involved in complementary action to lead to thymotropism.