Primary and secondary structures of Tetrahymena and aphid 5.8S rRNAs: structural features of 5.8S rRNA which interacts with the 28S rRNA containing the hidden break.

摘要

The Tetrahymena 5.8S rRNA is 154 nucleotides long, the shortest so far reported except for the split 5.8S rRNAs of Diptera (m5.8S plus 2S rRNA). In this molecule several nucleotides are deleted in the helix e (GC-rich stem) region. Upon constructing the secondary structure in accordance with "burp-gun" model, the Tetrahymena 5.8S rRNA forms a wide-open "muzzle" of the terminal regions due to both extra nucleotides and several unpaired bases. The aphid 5.8S rRNA consists of 161 nucleotides and can form stable helices in both terminal and helix e regions. As a whole, the secondary structure of Tetrahymena 5.8S rRNA resembles that of Bombyx 5.8S molecule while the aphid 5.8S rRNA shares several structural features with the HeLa 5.8S molecule. Likely, the 5.8S rRNA attached to the 28S rRNA with the hidden break differs in structure from those interacting with the 28S partners without the break. Nucleotide sequences of 5.8S rRNA in insects as well as in protozoans are not so conservative evolutionarily as in vertebrates.