Tong SE, Porton B, Pagtakhan J; International Conference on AIDS.

Int Conf AIDS. 1993 Jun 6-11; 9: 149 (abstract no. PO-A05-0087).

UCSF, Dept. of Med.

High level expression of HIV-1 requires a viral protein. Tat (trans-activator of transcription)-1, which acts on the trans-acting responsive region (TAR)-1 transcribed from positions +1 to +60 in HIV-1 long terminal repeat (LTR). TAR-1 forms a single stem-loop secondary RNA structure. High level expression of HIV-2 also requires its trans-activator, Tat-2; however, TAR-2 is transcribed from +1 to +125 in HIV-2 LTR and forms a double stem-loop RNA structure. We studied the function of Tat-2 in trans-activation of HIV-1 and HIV-2 in transient transfection assays in a human CD4+ T cell line, Jurkat. Previous investigators found that Tat-2 did not trans-activate the single stem loop of HIV-1 LTR. We find, however, that Tat-2 trans-activates HIV-1 LTR by 110-fold when the two exons of tat-2 are expressed as cDNA. Trans-activation (TA) of the HIV-1 LTR decreases to 32-fold when the genomic form of tat-2 is co-transfected; titration studies show that TA increases with increasing amounts of plasmid that express genomic tat-2. Trans-activation of the HIV-1 LTR is markedly decreased (11-fold TA) when only exon 1 (99 a.a.) of tat-2 is expressed. In contrast to genomic tat-2, however, titration studies show that TA does not increase with increasing amounts of plasmid that express exon 1 of tat-2. Exon 1 of Tat-2 trans-activates the HIV-2 LTR by 80-fold. The genomic form of tat-2 results in more efficient TA (104-fold) and full-length Tat-2 trans-activates HIV-2 LTR most efficiently (350-fold TA). Deletion studies show that basic residues in exon 2 of Tat-2 are required for optimal trans-activation of HIV-1 and HIV-2 LTRs. In sum, these findings suggest that genomic tat-2 is only partially spliced and expresses both an inefficient Tat-2 from exon 1 and an efficient full-length Tat-2. The 31 amino acids encoded by exon 2 of tat-2 allow this trans-activator to overcome the requirement for a double stem-loop as its target.

Publication Types:

• Meeting Abstracts

Keywords:

• Exons
• Gene Products, tat
• Genes, tat
• HIV Long Terminal Repeat
• HIV-1
• HIV-2
• Humans
• Plasmids
• RNA
• Trans-Activation (Genetics)
• Trans-Activators
• Transcription, Genetic
• Transfection
• genetics

Other ID:

• 93333516

UI: 102202890

From Meeting Abstracts