Objectives: To study the role of the hematopoietic transcription factor GATA-2 in long terminal repeat (LTR)-directed transcriptional activation of HIV-1 in hematopoietic progenitor cells, and to investigate possible GATA-2 binding sites in HIV-1 LTR.
Design and methods: Wild-type HIV-1 LTR, or mutants, ligated to a luciferase reporter gene with or without a GATA-2 expression vector, were transfected into COS cells, and standardized luciferase activity was examined. The binding activity of GATA-2 to these sites was examined by electrophoretic mobility shift assay. These wild-type or mutant reporter genes were also transfected into the murine hematopoietic progenitor cells, BAF3, in which GATA-2 was the predominantly expressed transcription factor of the GATA family, to assay LTR-directed transcription in intact hematopoietic machinery. Using a Tat expression plasmid for cotransfection, the influence of Tat protein on GATA-2-induced transactivation was determined.
Results: In COS cells, LTR-dependent transactivation was highly enhanced by the coexpression of GATA-2. Experiments with mutant LTR suggested the presence of multiple GATA-2 binding sites, of which the major sites were identified. Cotransfection of Tat with GATA-2 indicated that GATA-2 and Tat synergistically enhanced the transcriptional activity. Transfection experiments in BAF3 cells showed that the disruption of these GATA sites diminished LTR-driven activity to 40% of the wild-type.
Conclusions: GATA-2 may be a key host cell regulator of HIV-1 expression in hematopoietic stem cells. Manipulating this transactivation may represent a valuable approach to controlling virus production in infected hematopoietic progenitors. To elucidate the possible interaction between GATA-2 and Tat protein in vivo might give new insights to the mechanism of impaired hematopoiesis in AIDS patients.