Lys-34, dispensable for integrase catalysis, is required for preintegration complex function and human...

Area of Science:

• Molecular biology
• Virology
• Biochemistry

Background:

• Retroviral integrases (INs) are essential for viral DNA integration into host genomes.
• INs function within large nucleoprotein complexes known as preintegration complexes (PICs).
• The N-terminal domain of HIV-1 IN contains conserved residues critical for its function.

Purpose of the Study:

• To investigate the roles of two conserved lysine residues (K34 and K46) in the N-terminal domain of HIV-1 IN.
• To determine the impact of mutations at these lysine residues on viral replication and integration.
• To elucidate the functional consequences of IN mutations on PIC assembly and maturation.

Main Methods:

• Site-directed mutagenesis was used to generate HIV-1 mutants with K34A and K46A substitutions in the IN N-terminal domain.
• Viral replication kinetics were assessed by measuring virus production in cell culture.
• In vitro integration assays were performed using recombinant IN proteins.
• A sensitive PCR-based assay was developed to quantify viral DNA integration.
• Complementation assays were used to assess the infectivity of mutant viruses.

Main Results:

• HIV-1(K46A) replicated similarly to wild-type virus, indicating K46 is not essential for replication.
• HIV-1(K34A) was replication-defective, despite recombinant IN(K34A) showing catalytic activity in vitro.
• Vpr-IN(K34A) could complement the infectivity defect of an IN active site mutant virus.
• A sensitive PCR-based assay revealed that HIV-1(K34A) and related mutants failed to integrate viral DNA (<1% of wild-type levels).

Conclusions:

• The K34A mutation disrupts higher-order interactions essential for PIC function and maturation.
• Catalytic activity of the IN enzyme alone is insufficient for viral integration and replication.
• Specific residues in the IN N-terminal domain play critical roles in the assembly and functional maturation of the PIC.