Functional domains of tat required for efficient human immunodeficiency virus type 1 reverse transcription

Tat expression is required for efficient human immunodeficiency virus type 1 (HIV-1) reverse transcription. In the present study, we generated a serie s of 293 cell lines that contained a provirus with a tat gene deletion (Del ta tat). Cell lines that contained Delta tat and stably transfected vectors containing either wild-type tat or a number of tat mutants were obtained s o that the abilities of these tat genes to stimulate HIV-1 gene expression and reverse transcription could be compared. tat genes with mutations in th e amino terminus did not stimulate either viral gene expression or HIV-1 re verse transcription. In contrast, tat mutants in the activation, core, and basic domains of Tat did not stimulate HIV-1 gene expression but markedly s timulated HIV-1 reverse transcription. No differences in the levels of viri on genomic RNA or tRNA(3)(Lys) were seen in the HIV-1 Delta tat viruses com plemented with either mutant or wild type tat. Finally, overexpression of t he Tat-associated kinases CDK7 and CDK9, which are involved in Tat activati on of HIV-1 transcription, was not able to complement the reverse transcrip tion defects associated with the lack of a functional tat gene. These resul ts indicate that the mechanism by which tat modulates HIV-1 reverse transcr iption is distinct from its ability to activate HIV-1 gene expression.