CHARACTERIZATION OF NUCLEAR PROTEINS THAT BIND TO THE REGULATORY TGATTGGC MOTIF IN THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 LONG TERMINAL REPEAT

We have recently elucidated the nature and function of transcription f actors present in Jurkat, glial and neuronal cells that interact with modulatory region B, the nuclear receptor responsive element, in the l ong terminal repeat of human immunodeficiency virus type 1 (HIV-1), Co nsidering the key role that the combination of host cell proteins play s in HIV-1 gene transcription, it appears essential to characterize pr oteins interacting with the adjacent region A, In vitro experiments re vealed that the 5'-TGATTGGiC-3' motif of region a is the target for at least three distinct proteins, one belonging to the nuclear factor I family, while two others are related to the cAMP response element bind ing (CREB) protein family, One of these proteins, present in DNA-prote in complex C2, is formed by distinct polypeptides of relative molecula r mess 43 000 and 50 000, We have purified the 43 kDa protein, which i s distinct from CREB-43, and have shown that renatured p43 is able to specifically interact with site A. Transient expression experiments wi th vectors containing wild-type or mutant motif A revealed that basal HIV-1 gene transcription in Jurkat cells is regulated by antagonistic effects of the site A binding proteins.