Nanoviruses: genome organisation and protein function

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Nanoviruses are ssDNA plant viruses with multipartite genomes.
• They share similarities with Circoviridae (mammalian/avian) and Geminiviridae (plant) families, which also possess circular ssDNA genomes.
• Geminiviruses have unique virions distinct from circoviruses.

Purpose of the Study:

• To explore the replication mechanisms of ssDNA viruses.
• To investigate the structural similarities of replication initiator (Rep) proteins across different ssDNA virus families.
• To understand the evolutionary relationships of ssDNA virus Rep proteins.

Main Methods:

• Comparative analysis of ssDNA virus replication modes.
• Three-dimensional structure determination of geminivirus and parvovirus Rep proteins.
• Analysis of Rep protein catalytic domains and evolutionary origins.

Main Results:

• Viruses with circular ssDNA genomes (monopartite or multipartite) replicate via rolling circle replication.
• Replication relies on virus-encoded Rep proteins that initiate ssDNA replication and resolve intermediates.
• Structural analysis revealed similarities in the catalytic domains of Rep proteins from geminiviruses and parvoviruses.
• ssDNA viruses utilize host polymerases and modulate host cell cycle for replication.

Conclusions:

• Rep proteins of ssDNA viruses share conserved catalytic domains, indicating functional and evolutionary relationships.
• These Rep proteins may represent evolutionary intermediates linking RNA-binding proteins to papovavirus origin-binding proteins.
• The findings enhance understanding of ssDNA virus replication and evolution.