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 polymeras e (pol) III transcription was inserted into the intron of yeast tRNA(Tyr) g ene. If a promoter and a terminator for pol II transcription flanked it, th e tRNA gene could be transcribed by pol II, but the transcripts could not b e processed into mature tRNAs. In contrast, tRNA gene could also be transcr ibed by pol III and the transcripts could be processed into mature tRNAs ev en 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 tRN A gene transcripts by pol II.