HIV-1 DIS stem loop forms an obligatory bent kissing intermediate in the dimerization pathway

Area of Science:

• Molecular Biology
• Virology
• Biophysics

Background:

• The human immunodeficiency virus type 1 (HIV-1) dimerization initiation sequence (DIS) is vital for genome dimerization.
• DIS forms a 'kissing complex' between complementary RNA hairpins, a key step for viral replication.
• Understanding DIS interaction kinetics is crucial for developing novel HIV-1 therapeutics.

Purpose of the Study:

• To investigate the real-time kinetics of HIV-1 RNA dimerization using single-molecule Förster resonance energy transfer (smFRET).
• To elucidate the dynamic pathways of kissing complex formation and dissociation.
• To identify intermediates involved in the formation of the mature extended duplex required for virion packaging.

Main Methods:

• Utilized single-molecule Förster resonance energy transfer (smFRET) to monitor individual HIV-1 RNA dimerization events in real-time.
• Analyzed the dynamics of kissing complex formation, dissociation, and extended duplex formation.
• Investigated the role of specific nucleotides (A272) and cations (Mg(2+), K(+)) in the dimerization process.

Main Results:

• Observed real-time formation and dissociation dynamics of individual kissing complexes.
• Identified a previously uncharacterized bent intermediate essential for extended duplex formation.
• Demonstrated that the conserved A272 nucleotide and Mg(2+) ions are critical for stabilizing this bent intermediate.

Conclusions:

• Proposed a minimal three-step dimerization pathway involving a kissing complex and a bent intermediate, driven by Mg(2+) ions.
• Provided a 3D model for the bent intermediate, offering insights into the structural requirements for HIV-1 RNA dimerization.
• Highlighted the potential of targeting the DIS interaction pathway for novel anti-HIV-1 drug development.