Periodic genome sequences facilitate packaging in a single-stranded DNA virus

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Icosahedral viruses package genomes into constrained capsids.
• Single-stranded DNA (ssDNA) viruses like øX174 package genomes concurrently with replication into preformed capsids.
• The mechanism of ssDNA genome accommodation within capsids is not fully understood.

Purpose of the Study:

• To investigate the role of sequence motifs in the øX174 genome during packaging.
• To elucidate the ssDNA viral DNA replication-packaging pathway.

Main Methods:

• Site-directed mutagenesis was used to alter sequence motifs in the øX174 genome, creating the mutant øX^DO5.
• Cells were co-infected with wild-type and øX^DO5 viruses to track genome replication and packaging.
• Comparative analysis of viral DNA replication and virion content was performed.

Main Results:

• Mutating sequence motifs in the øX^DO5 genome resulted in packaging defects.
• Replication of øX^DO5 genomes was comparable to wild-type early in the infection.
• Significantly fewer øX^DO5 genomes were found within mature virions compared to wild-type.

Conclusions:

• Periodic sequence motifs in the øX174 genome are crucial for efficient viral genome packaging.
• These findings suggest selective pressure on ssDNA viral genomes to maintain specific packaging-related sequence patterns.
• The study highlights a defect in the transition from packaging intermediates to mature virions for the øX^DO5 mutant.