THE TRANS-INHIBITORY REP78 PROTEIN OF ADENOASSOCIATED VIRUS BINDS TO TAR REGION DNA OF THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 LONG TERMINAL REPEAT

The large rep gene products, Rep78 and Rep68, of adeno-associated viru s (AAV) are pleiotropic effector proteins which are required for AAV D NA replication and the transregulation of AAV gene expression, Apart f rom these essential functions prerequisite for the life cycle of AAV, these rep products are able to inhibit the replication and gene expres sion of human immunodeficiency virus type 1 (HIV-1) and a number of DN A viruses, Here, it is demonstrated that Rep78, as a chimeric with the maltose binding protein, directly binds the full-length HIV-1 long te rminal repeat (LTR), and to a subset of these sequences containing the tr nirs-activation response (TAR) sequence as DNA, These interactions , an effector protein physically binding a target promoter, suggest a direct mechanism of action for Rep78 inhibition, Furthermore, competit ive binding studies between the TAR region and the full-length HIV-LTR , strongly suggested that another site(s) within the LTR was also boun d by Rep78, Finally, as Rep78 binding is also believed to be affected by secondary structure within the DNA, it was found that Rep78 prefere ntially binds with HIV-LTR sequences with promoted secondary structure generated by heat denaturation and rapid cooling.