Structural basis for functional tetramerization of lentiviral integrase.

Area of Science:

• Structural biology
• Virology
• Molecular biology

Background:

• Retroviral DNA integration into host chromosomes is mediated by integrase (IN).
• A tetrameric form of IN is proposed to be essential for the concerted strand transfer reaction.
• LEDGF is a common lentiviral integration co-factor that binds IN.

Purpose of the Study:

• To elucidate the structural basis of IN tetramer formation and its role in concerted integration.
• To investigate the interaction between maedi-visna virus IN and the LEDGF co-factor.
• To understand how IN tetramer architecture facilitates the integration of both ends of retroviral DNA.

Main Methods:

• X-ray crystallography to determine the structure of IN-LEDGF complexes.
• Biochemical assays to assess IN tetramerization and integration activity.
• Mutagenesis studies to probe the function of the dimer-dimer interface.

Main Results:

• Two crystal structures reveal the dimer-of-dimers architecture of the IN tetramer, stabilized by N-terminal domain swapping.
• The flexible dimer-dimer interface closure was modeled, positioning active sites for concerted integration.
• The dimer-dimer interface is essential for HIV-1 IN tetramerization, in vitro integration, and virus infectivity.
• Adaptable interfaces allow divergent lentiviruses to use the conserved LEDGF co-factor.

Conclusions:

• The IN tetramer's dimer-of-dimers structure is critical for concerted integration.
• The dimer-dimer interface plays a vital role in viral infectivity.
• Structural insights into IN-LEDGF interactions explain co-factor utilization across lentiviruses.