A Ishimoto

Genistein, a protein tyrosine kinase inhibitor, suppresses the fusogenicity of Moloney murine leukemia virus envelope protein in XC cells

Summary. XC cells are highly susceptible to syncytium formation by infection of ecotropic murine leukemia viruses (MLVs) and by expression of their envelope protein (Env). By this property, XC cells are widely used to determine titers of ecotropic MLVs. Number of plaques resulted from the syncytium formation in XC cells by ecotropic MLV infection is corresponding to number of the viral particles. XC cells had been established from a v-src-induced rat tumor. It has been reported that transformed cells are more sensitive to Mo-MLV-induced syncytium formation than non-transformed cells. To assess whether the transformation by v-src oncogene in XC cells is involved in the high sensitivity to ecotropic MLV-induced syncytium formation, XC cells were treated with genistein, a protein tyrosine kinase inhibitor. Genistein suppressed the syncytium formation between XC cells and ecotropic Env-expressing 293T cells. This result indicates that protein tyrosine kinase activity is associated with the high sensitivity of XC cells to ecotropic Env-induced syncytium formation.

COMPARATIVE STUDIES ON TAT MUTANTS OF THREE PRIMATE LENTIVIRUSES

SummaryA frame-shifttat gene mutant of human immunodeficiency virus type 1 (HIV-1), which showed no detectable trans-activation potential, was constructed in vitro. Upon transfection, this clone directed the synthesis of virus mRNAs,gag proteins and virion-associated reverse transcriptase (RT) at a low level as was observed with thetat mutants of HIV-2 and simian immunodeficiency virus isolated from African green monkey (SIVAGM). Using these mutant viruses, trans-activation efficiency of viral gene expression bytat was compared among HIV-1, HIV-2, and SIVAGM. SIVAGM seemed to be less dependent ontat for RT production than HIV-1 and HIV-2.

Growth ability of auxiliary gene mutants of human immunodeficiency virus types 1 and 2 in unstimulated peripheral blood mononuclear cells

SummaryMutational studies on the Vif, Vpr, Vpu, Vpx, and Nef genes of human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2) were performed to evaluate their biological functions in natural target cells. For this purpose, replication properties of mutant viruses derived from HIV-1 NL strain and HIV-2 GH strain in unstimulated peripheral blood mononuclear cells were determined. Vif− viruses of both HIV-1 and HIV-2 did not grow at all in these cells. Similarly, no replication of HIV-2 Vpx− mutant was detected. In contrast, both of Vpr− and Nef− viruses of HIV-1 and HIV-2, and Vpu− virus of HIV-1 grew quite well in the cells. These results show, together with the data previously reported, that only Vif and Vpx are essential for HIV replication in primary blood cell cultures.

Genetic characterization of simian immunodeficiency virus isolated from an African mandrill

SummaryWe constructed an infectious molecular clone of simian immunodeficiency virus from an African mandrill (SIVMND). Upon transfection, this clone directed the production of progeny virus particles infectious to and cytopathic for CD4+ human leukemia cells. Thirteen frameshift proviral mutants with an alteration in the eight open reading frames of SIVMND were generated by recombinant DNA techniques, and were analyzed biologically and biochemically. While mutations in the structural genesgag, pol, andenv abolished viral growth and induction of cytopathology, mutants of thevif, vpr, andnef genes were fully biologically active. Of thetat andrev mutants, only onerev mutant grew in CD4+ cells with delayed kinetics. In reporter-based transient expression systems, transactivation potentials of thetat andrev mutants were evaluated. A mutant lacking 2nd coding exon oftat gene exhibitedtat activity similar to that of the wild type clone. The infectiousrev mutant was partially defective forrev gene activity.