satellite RNAs

Satellite-RNAs (satRNAs) is a broad term consisting of two major classes of viral satellites: satellite viruses and satellite nucleic acids. While satellite viruses depend on their helper virus for replication, they encode their own capsid proteins. Unlike satellite viruses, satellite nucleic acids are encapsidated with their helper virus. Within the category of small satRNAs (less than 500 nt), both linear and circular RNA species are known to be encapsidated. Notably, both linear and circular satRNAs can replicate via the rolling circle mechanism. Furthermore, both types of small satRNA are known to have ribozymes capable of self-cleavage in at least one polarity. Fascinatingly, the rolling circle-replicating linear satRNA of tobacco ringspot virus contains different self-cleaving ribozymes in each polarity: one a hammerhead (as in viroids) in the (+) strand and the other a hairpin in the (−) strand.
Circular satRNAs, which are restricted to the members of the Sobemovirus family, bear such similarity to viroids that they have been termed "virusoids". These satRNAs have (+) hammerhead ribozymes but, with the exception of the Lucerne transient streak virus satRNA, lack (−) ribozymes. This has given rise to the hypothesis that these satRNAs replicate by both symmetric and asymmetric rolling circles akin to the replication mechanisms of the pospiviroids and avsunviroids, respectively.

Sources:

  • Roossinck, M. J., Sleat, D., & Palukaitis, P. (1992). Satellite RNAs of plant viruses: structures and biological effects. Microbiological Reviews, 56(2), 265–279. https://doi.org/10.1128/mr.56.2.265-279.1992
  • Palukaitis, P. (2016). Satellite RNAs and Satellite Viruses. Molecular Plant-Microbe Interactions®, 29(3), 181–186. https://doi.org/10.1094/mpmi-10-15-0232-fi
  • Shen, W.-X., Au, P. C. K., Shi, B.-J., Smith, N. A., Dennis, E. S., Guo, H.-S., Zhou, C.-Y., & Wang, M.-B. (2015). Satellite RNAs interfere with the function of viral RNA silencing suppressors. Frontiers in Plant Science, 6. https://doi.org/10.3389/fpls.2015.00281
Name Accession Bases Type Family Genus
Velvet tobacco mottle virus Satellite RNA isolate K1v HQ680397.1 366 satellite RNA
Arabis mosaic virus small satellite RNA NC_001546.1 300 satellite RNA
Rice yellow mottle virus satellite NC_003380.1 220 satellite RNA
Cereal yellow dwarf virus-RPV satellite RNA NC_003533.1 322 satellite RNA
Lucerne transient streak virus satellite RNA NC_003798.1 324 satellite RNA
Solanum nodiflorum mottle virus satellite RNA NC_003850.1 377 satellite RNA
Subterranean clover mottle virus satellite RNA NC_003851.1 388 satellite RNA
Tobacco ringspot virus satellite RNA NC_003889.1 359 satellite RNA
Velvet tobacco mottle virus Satellite RNA NC_003906.1 366 satellite RNA
Arabis mosaic virus small satellite RNA barley/CHE/1991 RNA3-VI NC_018451.1 301 satellite RNA