Direct interactions between autoantigen La and human immunodeficiency virus leader RNA

Area of Science:

• Molecular Biology
• Virology
• RNA Biology

Background:

• The human immunodeficiency virus type 1 (HIV-1) leader RNA, known as the trans-activation response element (TAR), plays a critical role in viral gene expression.
• Understanding the interactions between viral RNA elements and host cell proteins is essential for deciphering viral replication mechanisms.

Purpose of the Study:

• To characterize the binding interaction between the human La protein and the HIV-1 TAR RNA element.
• To elucidate the structural requirements for La protein binding to TAR RNA.
• To investigate the functional implications of the La-TAR interaction in HIV-1 post-transcriptional regulation.

Main Methods:

• Immunoprecipitation studies using anti-La serum to detect La-TAR ribonucleoproteins in infected cells.
• In vitro binding assays to determine La protein's RNA binding preferences.
• Competition studies with various RNA molecules to assess binding specificity.
• Analysis of deletion mutants of the La protein to map its RNA binding domain.

Main Results:

• Human La protein was found to bind to HIV-1 TAR RNA both in vivo and in vitro.
• La protein preferentially binds to the stem region of TAR RNA, with recognition dependent on conserved secondary structure rather than primary sequence.
• The RNA binding domain of La protein for TAR RNA overlaps with its binding domain for polymerase III precursor transcripts.
• Direct interaction between La and TAR RNA was confirmed, suggesting a role in translational regulation.

Conclusions:

• The human La protein directly interacts with the HIV-1 TAR RNA element.
• This interaction is structurally specific, emphasizing the importance of RNA secondary structure for La binding.
• The findings provide insights into the translational control of HIV-1 mRNAs, highlighting the role of host factors like La protein.