THE SINGLE-STRANDED-DNA BINDING-PROTEIN, PUR-ALPHA, BINDS HIV-1 TAR RNA AND ACTIVATES HIV-1 TRANSCRIPTION

Previous studies indicate that the bulge and loop domains of TAR, the HIV-1 RNA regulatory element, bind viral and cellular factors that are critical for efficient transcription of the HIV-1 genome. In this rep ort, we demonstrate that the cellular protein, Pur-alpha, a previously characterized sequence specific, single-stranded DNA binding protein, binds to HIV-1 TAR RNA in a specific manner as demonstrated by compet ition analysis. Pur-alpha binds to the greatest extent to wild-type TA R RNA, and it appears the primary sequence, as well as the secondary s tructure and its overall stability contribute to this binding. Results from gel shift analysis using mutant Pur-alpha proteins indicate that amino acids 55-85, which contain the first of three basic aromatic re peats, are important for its binding to TAR RNA. Overexpression of Pur -alpha in a glial cell line increased transcription of HIV-1 LTR by a TAR dependent mechanism. The potential contribution by Pur-alpha to HI V-1 expression in relation to basal transcription by cellular factors is discussed. (C) 1998 Elsevier Science B.V.