BCL6 CAN REPRESS TRANSCRIPTION FROM THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-I PROMOTER ENHANCER REGION/

The gene BCL6 encodes a zinc finger protein with similarities to trans cription factors. We previously reported that a number of viral genome s, including human immunodeficiency virus type (HIV-I), contain sequen ces which are similar to the BCL6 DNA-binding consensus in their promo ter regions. Electrophoretic mobility shift assays showed that the ful l-length BCL6 protein extracted from transfected COS cells and a bacte rially expressed truncated protein containing the BCL6 zinc fingers ca n bind specifically to DNA from the U3 promoter/enhancer region of HIV -I. Transient transfections were performed to analyze the effects of t he BCL6 protein on luciferase expression driven by the HIV-I long term inal repeat (LTR) sequences. Full-length BCL6 significantly repressed luciferase activity compared with multiple controls. We conclude that the BCL6 protein can bind to the HIV-I promoter-enhancer region and co ntains a domain upstream of its zinc fingers that can repress transcri ption from the HIV-I LTR. (C) 1997 Wiley-Liss, Inc.