SITE SELECTION BY THE TRANSFER RNA SPLICING ENDONUCLEASE OF XENOPUS-LAEVIS

To investigate the mechanism by which the purified Xenopus tRNA splicing endonuclease recognizes its splice sites, we utilized yeast pre-tRNA3Leu and pretRNA Phe variants constructed by in vitro mutagenesis. We found that the endonuclease interacts with conserved features of the mature tRNA domain. In particular, U8 and C56 may be examples of contact points between protein and RNA. Given that there are no conserved sequences at the splice junctions, the specificity of cutting at both splice sites is determined by the length of the anticodon stem. Although in general, the sequence of the intron is unimportant for splicing, there are some structural requirements.