A new NMR solution structure of the SL1 HIV-1Lai loop-loop dimer

Area of Science:

• Molecular Biology
• Virology
• Structural Biology

Background:

• Genomic RNA dimerization is essential for human immunodeficiency virus type 1 (HIV-1) virion maturation and encapsidation.
• The RNA dimerization initiation site (DIS) is a critical element that initiates this process.
• Understanding the structure of DIS in solution is key to deciphering viral replication mechanisms.

Purpose of the Study:

• To elucidate the solution structure of the RNA dimerization initiation site (DIS) of HIV-1(Lai).
• To investigate the molecular interactions stabilizing the DIS structure.
• To explore potential conformational dynamics of the DIS.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy, including pulsed field-gradient spin-echo and multidimensional heteronuclear techniques.
• Analysis of RNA structural features and base pairing interactions.
• Comparison with existing crystallographic data.

Main Results:

• The DIS structure consists of two hairpins interconnected by six Watson-Crick GC base pairs.
• Intra- and intermolecular interactions involving adenines A8, A9, and A16 stabilize the hinges between stems and loops.
• While coaxial alignment of helices is supported, adenines A8 and A9 adopt a bulged-in position, suggesting conformational flexibility.

Conclusions:

• The determined solution structure provides new insights into the molecular organization of the HIV-1 DIS.
• The identified stabilizing interactions highlight key features for RNA dimerization.
• Evidence suggests an equilibrium between bulged-in and bulged-out conformations, implying dynamic structural behavior crucial for viral function.