The effects of protein synthesis inhibition, and of mutations rna1.1 and rna82.1, on the synthesis of small RNAs in yeast

Strains of Saccharomyces cerevisiae have been constructed that possess temperature-sensitive defects in tRNA precursor (pre-tRNA) splicing and which also lack the processing endonuclease that acts at the 3'-terminus of 5 S rRNA and 35 S rRNA precursors (pre-rRNAs). The unspliced pre-tRNAs accumulated by such strains at the nonpermissive temperature are identical in structure to those accumulated by pre-tRNA splicing-defective strains with a functional pre-5 S RNA processing enzyme. The pre-RNA processing activity is therefore not obligatorily involved in maturation of several yeast tRNAs. However, gels of the pulse-labelled RNAs of RNA82+ and rna82.1 strains provide evidence that this enzyme acts upon a few small unstable transcripts that are not 5 S RNA forms. The most prominent of these transcripts on gels was, in wild-type strains, an RNA 145 +/- 2 nucleotides in length.