Dynamics of Human Immunodeficiency Virus Transcription: P-TEFb Phosphorylates RD and Dissociates Negative Effectors from the Transactivation Response Element

Abstract

The elongation of transcription is a highly regulated process that requires negative and positive effectors. By binding the double-stranded stem in the transactivation response (TAR) element, RD protein from the negative transcription elongation factor (NELF) inhibits basal transcription from the long terminal repeat of the human immunodeficiency virus type 1 (HIVLTR). Tat and its cellular cofactor, the positive transcription elongation factor b (P-TEFb), overcome this negative effect. Cdk9 in P-TEFb also phosphorylates RD at sites next to its RNA recognition motif. A mutant RD protein that mimics its phosphorylated form no longer binds TAR nor represses HIV transcription. In sharp contrast, a mutant RD protein that cannot be phosphorylated by P-TEFb functions as a dominant-negative effector and inhibits Tat transactivation. These results better define the transition from abortive to productive transcription and thus replication of HIV.

We thank members of the Peterlin laboratory for help with experiments, Hiroshi Handa for reagents, and Warner Greene, Hiroshi Handa, Jonathan Karn, Eric Verdin, and Keith Yamamoto for comments on the work. We thank Lindsey McGowen for technical assistance.

This study was supported in part by grants from AmFAR, Center for AIDS Research in CWRU, NIH, and UARP.