INHIBITION OF HIV-1 REPLICATION IN VIRAL MUTANTS WITH ALTERED TAR RNASTEM STRUCTURES

Human immunodeficiency virus type 1 (HIV-1) Tat-mediated trans-activat ion requires the structural integrity of TAR RNA and the cooperative i nteraction of human host cell proteins. The TAR domain, minimally requ ired for tar response, includes the Tat binding pyrimidine bulge, the TAR RNA upper stem, and the loop sequences. However, little is known a bout the significance of the 5'-stem structure of TAR in the regulatio n of viral growth. We designed viral mutations, specifically in the TA R RNA lower stem structure, and studied their effects on the kinetics of viral growth in T-lymphocyte cell lines and in activated human peri pheral blood mononuclear cells. Mutations that destabilized the lower TAR stem structure inhibited viral growth to various degrees in differ ent CD4+ T-cells. These results suggest that the structural integrity of the lower stem structure of TAR plays an important role in viral gr owth, presumably by binding to specific host cell proteins that stabil ize Tat-TAR interactions. (C) 1996 Academic Press, Inc.