Abstract
Maf1 is negative regulator of RNA polymerase III in yeast. We observed high levels of both primary transcript and end-matured, intron-containing pre-tRNAs in the maf1Δ strain. This pre-tRNA accumulation could be overcome by transcription inhibition, arguing against a direct role of Maf1 in tRNA maturation and suggesting saturation of processing machinery by the increased amounts of primary transcripts. Saturation of the tRNA exportin, Los1, is one reason why end-matured intron-containing pre-tRNAs accumulate in maf1Δ cells. However, it is likely possible that other components of the processing pathway are also limiting when tRNA transcription is increased. According to our model, Maf1-mediated transcription control and nuclear export by Los1 are two major stages of tRNA biosynthesis that are regulated by environmental conditions in a coordinated manner.
Highlights
The existence of three RNA polymerases (Pol)2 is documented for all investigated eukaryotes
To assess whether tRNA transcription is coordinated with any part of the post-transcriptional tRNA biosynthesis process, we explored the possibility that perturbation of Maf1-mediated control of transcription could affect tRNA processing
The increased levels were verified by analyses employing microarrays that contained sequences of all of the different yeast tRNA families and other genes transcribed by the Pol III [33]
Summary
The existence of three RNA polymerases (Pol)2 is documented for all investigated eukaryotes. We observed high levels of both primary transcript and end-matured, intron-containing pre-tRNAs in the maf1⌬ strain. The results showed that the double mutant accumulated elevated levels of both initial transcript and intron-containing end-matured precursor (Fig. 2).
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