Identification of a protein factor binding to the 5′-flanking region of a tRNA gene and being involved in modulation of tRNA gene transcriptionin vivoinSaccharomyces cerevisiae

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Abstract
Control mechanisms of tRNA gene transcription were studied in vivo in Saccharomyces cerevisiae . In order to be able to monitor in vivo transcription products of an individual tRNA gene, a ‘tester gene’ was used which is readily transcribed in vivo in yeast but does not cross-hybridize with any cellular yeast tRNA. A series of insertion mutants were constructed, modifying thereby the immediate and further distant 5′-flanking region of the ‘tester tRNA gene’. Small linker molecules of different length and different sequence were inserted at positions -3 and -56 on the non-coding strand. Resulting tRNA gene variants were transformed into yeast cells and in vivo synthesized products were monitored by primer extension analysis. From the experimental data we suggest that a few essential nucleotides within the flanking region are able to determine the in vivo transcription activity of the ‘tester tRNA gene’. Our results are rationalized on a biochemical level by protein binding assays: At least one protein binds to the 5′-flanking region of the ‘tester tRNA gene’ and different protein complexes are sequestered on active or less active tRNA gene variants.