Recombination in large RNA viruses: Coronaviruses

Coronaviruses contain a very large RNA genome, which undergoes recombination at a very high frequency of nearly 25% for the entire genome. Recombination has been demonstrated to occur between viral genomes and between defective-interfering (DI) RNAs and viral RNA. It provides an evolutionary tool for both viral RNAs and DI RNA and may account for the diversity in the genomic structure of coronaviruses. The capacity of coronaviruses to undergo recombination may be related to its mRNA transcription mechanism, which involves discontinuous RNA synthesis, suggesting the nonprocessive nature of the viral polymerase. Recombination is used as a tool for the mutagenesis of viral genomic RNA. (C) 1996 Academic Press Ltd.