Evolution from semi-tRNA to tRNAs, rRNAs, snRNA and primitive mRNAs

Koji Ohnishi

Dept. Biol., Fac. Sci., Niigata Univ.

Prokaryotic tRNA and tRNA and some other tRNAs seem to well conserve primitive tRNA (proto-tRNA) commonly ancestral to all contemporary tRNAs. The 5'- and 3'-halves of the E.coli (EC) tRNA(62,114) = 0.21 X 10. This well coinsides with Noller et al's (1992) recent experimental result that large-subunit rRNA has a PT activity. U1 snRNA and some possibly primitive mRNAs also showed significant levels of base sequence similarity, suggesting that some snRNAs and primitive mRNAs most probably emerged from tRNA-like or semi-tRNA-like primitive RNA(s).