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).