Structural and Functional Properties of HIV-1(GER) TAR Sequences

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• The human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) regulates viral gene expression.
• The trans-activating region (TAR) is crucial for HIV-1 replication and is targeted by the viral Tat protein.

Purpose of the Study:

• To investigate the structural and functional characteristics of the HIV-1(GER) LTR.
• To determine the impact of TAR sequence duplication on Tat transactivation efficiency.

Main Methods:

• Sequencing of the HIV-1(GER) LTR.
• Analysis of LTR-chloramphenicol acetyltransferase (CAT) reporter constructs.
• Assessment of Tat transactivation in CEM cells.

Main Results:

• A novel TAR duplication (TAR1 and TAR2) was identified in the HIV-1(GER) LTR, stable during replication.
• The duplicated TAR sequence significantly increased LTR-CAT reporter gene expression under Tat transactivation compared to a single TAR sequence.
• Only the 5' transcription initiation site in the HIV-1(GER) LTR was functionally active.
• The predicted secondary structure of HIV-1(GER) mRNA resembles that of HIV-2, forming a double TAR hairpin.
• HIV-1(GER) Tat protein exhibited sequence similarity to other HIV-1 Tat proteins but not to HIV-2 Tat proteins.

Conclusions:

• The study provides the first evidence of a TAR sequence duplication in HIV-1.
• This duplication enhances Tat protein-mediated transactivation, increasing viral gene expression efficiency.
• The findings contribute to understanding HIV-1 LTR structure-function relationships and viral replication mechanisms.