| Rice yellow mottle virus satellite circular RNA (scRYMV), is a covalently closed, highly self-complementary RNA, often associated with rice yellow mottle sobemovirus (RYMV). A head-to-tail trimer clone (pET52) of the 220 nt scRYMV, was expressed in E. coli to study its protein coding capacity, translational strategy and hammerhead ribozyme activity. Besides the expected 19 kD fusion protein generated from the scRYMV open reading frame (ORF) fused with the S•Tag/thrombin ORF in plasmid pET29, this study showed the synthesis of a secondary 16 kD minor product, likely via internal translation initiation. Additionally, in vitro experiments suggested that termination suppression may also occur to generate an 18 kD extended version of the 16 kD protein.;Furthermore, expression of pET52 in E. coli was observed to induce host RNA fragmentation (20-75 nt). Subsequently, the expression of a transcript carrying a small hairpin-loop was shown to be sufficient to trigger the fragmentation phenomenon. |
