Correct splicing of modified introns of a Rhizopus proteinase gene in Saccharomyces cerevisiae.

The intron of the Rhizopus aspartic proteinase gene (RNAP-I) was modified by in vitro mutagenesis and examined for its splicing efficiency in Saccharomyces cerevisiae. The wild-type intron of the RNAP-I gene was not spliced at all in spite of its structural similarity to introns of S. cerevisiae. The primary transcript of the RNAP-I gene was converted to correctly translatable mRNA only when the complete consensus sequence of S. cerevisiae introns (i.e. 5'-GTATGT-----TACTAAC-----TAG-3') was introduced into its intron, although the efficiency of splicing was low. It is also shown that transformants carrying the RNAP-I gene with the complete consensus sequence of S. cerevisiae introns produce active RNAP-I protein.