Establishing a genetic recombination map for murine coronavirus strain A59 complementation groups.

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Murine hepatitis virus (MHV-A59) is a nonsegmented, linear, plus-polarity RNA virus.
• Understanding the genetic organization and recombination mechanisms of MHV-A59 is crucial for elucidating its replication cycle and pathogenesis.

Purpose of the Study:

• To isolate and characterize temperature-sensitive (ts) mutants of MHV-A59.
• To determine the genetic map and recombination frequencies within the MHV-A59 genome.
• To investigate the timing of recombination during the virus replication cycle.

Main Methods:

• Isolation and characterization of MHV-A59 ts mutants representing RNA+ and RNA- complementation groups.
• Genetic recombination techniques to determine recombination frequencies and map mutations.
• Analysis of recombination frequencies under varying multiplicities of infection and at different stages of the virus growth cycle.

Main Results:

• Recombination frequencies were significantly higher (63-20,000 times) than spontaneous reversion frequencies.
• Recombination is a late event in the MHV-A59 replication cycle, peaking late in infection.
• A linear genetic map of five RNA- complementation groups was constructed within the 5' end of the 23-kb polymerase region.
• Recombination frequency for the entire 32-kb MHV genome approached or exceeded 25%.

Conclusions:

• At least five distinct functions involved in virus transcription are encoded within the MHV polymerase region.
• MHV-A59 exhibits a high recombination frequency for a nonsegmented, linear, plus-polarity RNA virus.
• The study provides a detailed genetic map and insights into the late-acting recombination mechanism of MHV-A59.