Tat And Tar Of Human Immunodeficiency Virus Hiv-1 Gene Expression Regulation

The Tat protein of human immunodeficiency virus type 1 (HIV-1) is a potent transactivator of viral gene expression, it can enhance the transcriptional initiation and elongation of HIV-1 gene expression; and it may also have additional functions in the pathogenesis of the acquired immunodeficiency syndrome (AIDS). Therefore, Tat is a desirable target for recombinant gene therapy against HIV-1 infection. The cis-acting response element (TAR) of Tat transactivator is a stem-loop structure RNA present within the first 60 nucleotides of all HIV-1 transcripts. Since Tat must bind to TAR RNA "bulge" region directly or indirectly via cellular factors in order to mediate its function, so TAR is also an optimal intervention target for the development of gene therapy. Previously our results have shown that a deleted mutant of HIV-1 LTR, YL158, which spans from -158 to +80, demonstrated the strongest promoter activity than the full length HIV-1 LTR and also other different deleted mutant LTR fragments. As this promoter contains TAR DNA sequence, it is Tat-regulated. In this work we use YL158 as our expression promoter.By means of mutational analysis, several domains of the HIV-1 Tat protein that are required for complete activation of HIV-1 gene expression have been defined. The Tat trans-activators encoded by the primate immunodeficiency virus (HIV-1, HIV-2 and SIV) share the same three highly conserved domains: Cystine-rich domain, core region and basic domain. Site-directed mutagenesis by PCR method of these regions in the tat gene of HIV-1 was shown to greatly reduce or abolish the transactivity of Tat protein when pM1-6 were cotransfected transiently...