HIV-1 Tat Interacts with Cyclin T1 to Direct the P-TEFb CTD Kinase Complex to TAR RNA

Abstract

Studies of viral transcription factors have yielded manyimportant insights into the different mechanisms that regulate RNA polymerase II (RNAPII) transcription. Thehuman immunodeficiency virus type-1 (HIV-1) proviralpromoter is induced strongly in cytokine-activated T cellsand macrophages and provides a useful system to studythe processes that control transcription initiation andelongation in a chromatin environment (Fig. 1). Becausethe virus has, on average, only 48 hours in an activated Tcell to complete its entire virus life cycle, it must transition quickly to an active transcription program followingintegration into the host-cell genome (for review, seeEmerman and Malim 1998). To respond to this challenge,HIV-1 evolved a compact and powerful enhancer whichis coupled to promoter and downstream control sequences that sharply restrict transcription elongation byRNAPII. This restriction establishes a requirement for thevirus-encoded regulatory protein, Tat, which is targetedto the nucleus and acts as an HIV-1 promoter-specifictranscription elongation factor (for review, see Jones an...