Expression of human foamy virus reverse transcriptase involves a spliced pol mRNA

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Human foamy virus (HFV) expresses reverse transcriptase (Pol) independently of Gag.
• The mechanism of Pol expression is crucial for viral replication.

Purpose of the Study:

• To investigate the role of a specific spliced mRNA in HFV Pol expression.
• To elucidate the significance of the splice acceptor site in the gag gene for Pol production and viral replication.

Main Methods:

• Identification of a spliced mRNA utilizing a novel splice acceptor site within the gag gene.
• Construction and analysis of an HFV mutant with a disrupted splice acceptor site.
• Replication assays using a sensitive lacZ reporter system under HFV LTR control.
• Indicator gene assays to explore alternative Pol expression mechanisms.

Main Results:

• A mutation in the splice acceptor site abolished detectable Pol protein expression and significantly reduced viral replication.
• Viral replication competence was restored over time, correlating with reversion of the mutated splice acceptor site.
• Evidence suggests a secondary, transactivator-dependent cryptic promoter in the gag gene contributes to Pol-encoding transcripts.

Conclusions:

• The spliced pol transcript is essential for efficient HFV replication.
• A second mechanism involving a cryptic promoter in the gag gene likely contributes to Pol expression.
• Understanding these Pol expression pathways is vital for controlling HFV replication.