SIMILARITIES BETWEEN THE SECONDARY STRUCTURE OF SATELLITE TOBACCO MOSAIC-VIRUS AND TOBAMOVIRUS RNAS

The secondary structure of satellite tobacco mosaic virus (STMV) RNA w as predicted using computer simulations of RNA folding. The analogies of structural elements in the 3' end untranslated regions (3'-UTR) of tobamoviral RNAs were analysed. In addition to the tRNA-like structure and pseudoknot stalk, which are found in all known RNAs of tobamoviru ses and STMV, another region of stable consecutive pseudoknots was pre dicted in the 3'-UTR of STMV RNA. A similar pattern of repeated struct ural units, containing pseudoknot stalks and parts of the tRNA-like st ructure, was also found in odontoglossum ringspot virus (ORSV) RNA 3'- UTR. The predictions on the structure are supported by sequence compar isons which point to an important functional role of 3' terminal pseud oknots in STMV RNA as well as in other tobamoviral RNAs. The possible participation of pseudoknotted structures in the interactions with coa t protein in STMV is discussed.