AEGiS-08IAC: Role of Tat and cellular factors in HIV-1 expression.

8th International AIDS Conference

Amsterdam, Netherlands — July 19-24, 1992

Role of Tat and cellular factors in HIV-1 expression.

Int Conf AIDS 1992 Jul 19-24; 8:We46 (abstract no. WeA 1006)
Gatignol A, Chang YN, Jeang KT; Laboratory of Molecular Microbiology, NIAID, NIH, Bethesda, MD 20892.

OBJECTIVES: Induction of HIV expression is due to activation by cellular and viral factors. Tat, the trans-activator of HIV-1 acts through an RNA target TAR (trans-activator responsive) to activate DNA elements in the promoter in an appropriate cellular setting. This suggests important interactions between Tat, DNA/RNA targets and cellular factors in order to increase transcription. We will describe the role of two cellular proteins that bind to TAR RNA. METHODS AND RESULTS: To obtain cDNAs that encode TAR RNA binding proteins, we assayed a HeLa cell library using an RNA recognition site probe. Two related cDNAs code for 37 and 42 kDa proteins called TRBP. A third one codes for La autoantigen. We showed by in situ filter binding and gel shift assays that TRBPs and La bind to TAR RNA. By mutational analysis of the protein, we determined the binding site of TRBP. In gel retardation assay, the corresponding peptide was sufficient to slow down a TAR RNA band indicating the formation of an RNA-peptide complex. This complex was competed away by HeLa cellular RNA, polyI-polyC and homologous RNA but not by DNA, single stranded or unstructured RNA. This suggests a short, double stranded RNA motif recognition for TRBP. This site is likely to exist in many copies in HeLa cellular RNA, the natural TRBP target. In vivo, TRBP activates HIV-1 LTR and other promoters. In cotransfection assays, we observed a synergistic function between Tat and TRBP on HIV-1 LTR.

CONCLUSIONS: TRBP may represent one member of a family of cellular proteins that is capable of influencing gene expression through the binding of RNA. We propose that Tat, TAR RNA and cellular factors act in a cooperative manner to activate HIV-1 LTR. The virus utilizes cellular proteins such as TRBP and La and may co-opt the corresponding cellular function in order to increase its own expression and/or stability.

Keywords: AEGIS, HIV Long Terminal Repeat, HIV-1, Antithrombin III, Peptide Hydrolases, RNA-Binding Proteins, RNA, Hela Cells, RNA Probes, Binding Sites, Transcription, Genetic, Trans-Activators, Promoter Regions (Genetics), antithrombin III-protease complex, TAR RNA-binding protein, Human, pharmacokinetics, genetics, ICA8
920719
WeA1006