Mutational analysis of sodium butyrate inducible elements in the human immunodeficiency virus type I long terminal repeat.

Sodium butyrate induces gene expression directed by the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) in HeLa cells. Inducible regions of the HIV-1 LTR were elucidated by using 5' and 3' LTR deletion mutants and LTR site-directed mutants within the Sp1 binding sites and the trans-activation responsive (TAR) region. Two LTR regions inducible by sodium butyrate were located: one at -117 to -103 (distal site) and one at -65 to -17 (proximal site). In HeLa cells trans-fected with pZ6neo, a biologically active HIV-1 proviral clone, sodium butyrate stimulated virus production following a 3-day treatment. Inducibility of HIV-1 gene expression by sodium butyrate was unrestricted in many human cell types, including CD4+ lymphoid cells and non-CD+ brain cells and fibroblasts. Additionally, sodium butyrate transiently induced HIV-2 LTR-directed gene expression in HeLa cells. Using the HIV-1SF-2 tat gene cotransfected with pLTR-CAT site-directed TAR mutants in HeLa cells, the boundaries of tat-trans-activation were delineated more precisely. These results suggest that the induction of HIV-1 gene expression is mediated by the interaction of sodium butyrate with cellular transcription factors that bind to the HIV-LTR.