Megabirnavirus (taxid:1285597)



Non-enveloped icosahedral capsid, about 50 nm in diameter. Presumably T=1 icosahedral symmetry but has not been determined.



Segmented linear dsRNA genome: 2 segments encoding potentially for 4 proteins. Segments are about 7 kb and 9 kb.


The coding strands of RNA-1 and RNA-2 contain two non-overlapping tandem ORFs. A single major capsid protein of 135 kDa is encoded by RNA-1. Translation is likely initiated by a unique internal ribosome entry site (IRES) element at the 5'-UTR.




  1. Virus penetrates into the cytoplasm.
  2. Transcription of the dsRNA genome by viral polymerase occurs inside the virion, so that dsRNA is never exposed to the cytoplasm. This plus-strand transcript is used as template for translation.
  3. (+)RNAs are encapsidated in virion particle, in which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
  4. Mature are transmitted to new cell during cell division, sporogenesis or cell fusion.
These structures were created with the help of Colabfold by Jason Nomburg, Nathan Price and Jennifer Doudna (ModelArchive).

Rosellinia necatrix megabirnavirus 1 (isolate -/Japan/W779/2001) taxid:658904

Protein ModelArchive
Capsid protein ma-jd-viral-55544
Coat protein ma-jd-viral-31409
RNA-directed RNA polymerase (EC ma-jd-viral-19880
Uncharacterized protein ma-jd-viral-64647

Rosellinia necatrix megabirnavirus 2-W8 taxid:1676267

Protein ModelArchive
Putative coat protein ma-jd-viral-31407
RNA-directed RNA polymerase (EC ma-jd-viral-19881
Uncharacterized protein ma-jd-viral-56954

Sclerotinia sclerotiorum megabirnavirus 1 taxid:1661257

Protein ModelArchive
Putative coat protein ma-jd-viral-31408
RNA-dependent RNA polymerase ma-jd-viral-43607
RNA-directed RNA polymerase (EC ma-jd-viral-19879