The HIV-1 Vpr co-activator induces a conformational change in TFIIB

Vpr is a HIV-1 virion-associated protein which plays a role in viral replic ation and in transcription and cell proliferation. We hale previously repor ted that Vpr stimulates transcription of genes lacking a common DNA target sequence likely through its ability to interact with TFIIB, However, the mo lecular mechanism of the Vpr-mediated transcription remains to be precisely defined, In this in vitro study, we show that the binding site of Vpr in T FIIB overlaps the domain of TFIIB which is engaged in the intramolecular br idge between the N- and C-terminus of TFIIB, highly suggesting that binding of Vpr may induce a change in the conformation of TFIIB, Indeed, with a pa rtial proteolysis assay using V8 protease, Ne demonstrate that Vpr has the ability to change the conformation of TFIIB, We investigated in this partia l proteolysis assay a series of Vpr-mutated proteins previously defined for their transactivation properties. Our data show a correlation between the ability of Vpr-mutated proteins to stimulate transcription and their abilit y to induce a conformational change in TFIIB, indicating a functional relev ance of the Vpr-TFIIB interaction. (C) 1999 Federation of European Biochemi cal Societies.