Global synonymous mutagenesis identifies cis-acting RNA elements that regulate HIV-1 splicing and replication.

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• The human immunodeficiency virus type 1 (HIV-1) genome encodes regulatory RNA sequences and structures crucial for viral replication.
• Previous studies suggest the presence of undiscovered RNA elements with unknown functions within the HIV-1 genome.

Purpose of the Study:

• To identify novel cis-acting RNA elements in the HIV-1 genome that are essential for viral replication.
• To investigate the role of these elements in regulating viral processes, particularly RNA splicing.

Main Methods:

• A global silent mutagenesis experiment was conducted using sixteen mutant proviruses with synonymous mutations across the HIV-1 protein-coding sequence.
• Phenotypic analysis of mutant viruses categorized them into groups based on replication efficiency and splicing patterns.
• Detailed characterization of replication-defective mutants, including the derivation of second-site revertants.

Main Results:

• Mutant viruses were classified into three groups based on replication and splicing phenotypes.
• Mutations causing replication defects were regionally biased and reduced unspliced RNA levels.
• Group 2 mutants showed splicing defects, and revertants often had mutations reducing splice site utilization, indicating RNA elements suppressing splice site usage.

Conclusions:

• The HIV-1 genome harbors complex regulatory RNA elements that negatively control viral splicing.
• These elements, distributed across the genome, are critical for maintaining balanced splicing and enabling efficient viral replication.
• The study uncovers a new layer of post-transcriptional regulation in HIV-1 replication.