Abstract

Many of the most medically and economically important viruses have genomes composed of RNA instead of DNA . Such viruses include influenza, hepatitis C, yellow fever, dengue, SARS , MERS, mumps, measles, ebola and rabies viruses. RNA virus genomes are extremely small (ranging from 2 to 32 kb) and evolve under selection pressures very different from those that bear on the genomes of cellular organisms. Virus replicative cycles and gene expression mechanisms also differ significantly from those of cellular organisms. Genomes commonly contain overlapping genes (where the same nucleotide sequence codes for different proteins in different reading frames) and functional RNA elements (e.g. RNA structures involved in replication, translational control or genome packaging) embedded within protein-coding sequences. Thus, techniques developed for cellular genome analysis are not always applicable to RNA virus sequences. On the other hand, RNA viruses evolve very rapidly and, for many species, there are many sequenced isolates with high intraspecies divergences so that comparative genomic analyses can be used at the single-species level. The seminar will cover an introduction to RNA viruses, non-canonical gene expression mechanisms, and some comparative genomic methods for investigating ‘hidden’ genes and non-coding functional elements in virus genomes.