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Nidovirales: evolving the largest RNA virus genome
Alexander E Gorbalenya1, Luis Enjuanes, John Ziebuhr
1Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, LUMC E4-P, P.O. Box 9600, 2300 RC Leiden, The Netherlands. a.e.gorbalenya@lumc.nl
Virus Research
|March 1, 2006
Summary
This review compares large and small animal RNA viruses within the order Nidovirales, highlighting common features in genome structure, replication, and evolution. It explores how RNA processing enzymes may have enabled genome expansion in these significant viral groups.
Area of Science:
- Virology
- Molecular Biology
- Evolutionary Biology
Background:
- Nidovirales is a monophyletic order of animal RNA viruses including coronaviruses, toroviruses, roniviruses, and arteriviruses.
- Large nidoviruses possess the largest known RNA genomes (26–32kb), while arteriviruses have smaller genomes (13–16kb).
Purpose of the Study:
- To review and compare common and unique features of large and small nidoviruses.
- To outline the genetic plan, genome diversity, replicase machinery, and evolutionary origins of Nidovirales.
Main Methods:
- Comparative analysis of viral genome structures and gene expression mechanisms.
- Review of RNA processing enzymes and their role in viral evolution.
Main Results:
- Nidoviruses utilize single-stranded, positive-polarity, polycistronic RNA genomes.
- Replicase gene expression involves ribosomal frameshifting and proteases; subgenomic RNAs express structural and accessory proteins.
- Unique RNA-processing enzymes in nidoviruses may have facilitated genome expansion and diversification.
Conclusions:
- Nidoviruses exhibit conserved replication strategies but significant diversity in genome size and accessory genes.
- Acquisition of RNA-processing enzymes is a key factor in the evolution of large nidovirus genomes.
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