Totivirus

Totivirus is a genus of viruses, in the family Totiviridae. Fungi serve as natural hosts. There are currently seven species in this genus including the type species Saccharomyces cerevisiae virus L-A. Group: dsRNA One species infects the fungus Saccharomyces cerevisiae. The Helminthosporium victoriae 190S virus which was initially included in this genus has been moved to a new genus—the Victorivirus. Species of this genus commonly infect the human pathogen Trichomonas vaginalis. Viruses in Totivirus are non-enveloped, with icosahedral symmetry, and T=2 architecture. The diameter is around 40 nm. Genomes are linear, around 4.6-6.7kb in length. The genome has 2 open reading frames. Totivirus have a genome of 4700–6700 nucleotides in length and only a single copy of the genome is present in the particle. The nucleic acid content of Totivirus is usually of one molecule but can also contain three or four segments of linear double stranded RNA. The genome contains two large overlapping open reading frames (ORFs). These open reading frames (ORFs) code for a capsid protein (CP) and an RNA-dependent RNA polymerase (RDRP). The 5' end of the positive strand of the dsRNA genome has no cap and is very structured.Totivirus contains a long 5' untranslated region (5' UTR) which functions as an internal ribosome entry site (IRES). Totiviruses can have satellite RNAs encoding a toxin. Viral replication is cytoplasmic. Entry into the host cell is achieved by virus remains intracellular. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. Translation takes place by -1 ribosomal frameshifting. The virus exits the host cell by cell-to-cell movement. Fungi serve as the natural host.