RNA polymerase II induced transcription of tRNA genes and processing of the mRNAs in yeast

Only 5’-halves were produced when the terminator sequence for RNA polymerase (pol) Ⅲ transcription was inserted into the intron of yeast tRNATyr gene. If a promoter and a terminator for pol Ⅱ transcription flanked it, the tRNA gene could be transcribed by pol Ⅱ, but the transcripts could not be processed into mature tRNAs. In contrast , tRNA gene could also be transcribed by pol Ⅲ and the transcripts could be processed into mature tRNAs even if a promoter and a terminator for pol Ⅱ transcription flanked it. Pol Ⅱ transcripts, modified with a self-cleaved hammerhead structure at 3’-end, were processed into mature tRNAs in the medium containing 100 mmol/L Mg2+ , indicating that the 3’-long trailer sequence blocks the maturation of tRNA gene transcripts by polⅡ.