Characterization of replication defects induced by mutations in the basic domain and C-terminus of HIV-1 matrix

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• The human immunodeficiency virus type 1 (HIV-1) matrix domain (MA) is crucial for viral replication and entry.
• Extensive mutagenesis studies have identified distinct functional regions within the MA protein.
• Understanding MA's role in viral entry is key to developing antiviral strategies.

Purpose of the Study:

• To delineate the specific functions of the N-terminal basic and C-terminal helical domains of HIV-1 MA in viral entry.
• To analyze the impact of mutations within these domains on viral infectivity, fusion, and envelope incorporation.

Main Methods:

• Site-directed mutagenesis was used to introduce deletions and mutations in the N-terminal and C-terminal domains of HIV-1 MA.
• Viral infectivity and fusion assays were performed to assess the functional consequences of mutations.
• Analysis of viral envelope incorporation into mature virions was conducted.
• The effect of truncating the gp41 cytoplasmic tail (gp41CT) was evaluated in specific mutants.

Main Results:

• Deletions in the C-terminal fifth helix of MA resulted in mild defects in infectivity and fusion, primarily due to reduced viral envelope incorporation.
• Truncation of the gp41CT could partially rescue the phenotype of C-terminal mutants.
• Mutations of multiple basic residues in the N-terminus of MA caused severe defects in infectivity and fusion.
• N-terminal mutations led to significant envelope incorporation defects and also impaired a post-entry step, as gp41CT truncation could not rescue infectivity.

Conclusions:

• The N-terminal basic region and C-terminal helical domain of HIV-1 MA play distinct roles in viral entry.
• N-terminal MA mutations severely disrupt viral entry at multiple stages, including post-entry.
• C-terminal MA mutations primarily affect viral envelope incorporation, with a lesser impact on overall infectivity.