Formation and nuclear export of tRNA, rRNA and mRNA is regulated by the ubiquitin ligase Rsp5p

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Abstract
The yeast ubiquitin‐protein ligase Rsp5p regulates processes as diverse as polII transcription and endocytosis. Here, we identify Rsp5p in a screen for tRNA export (tex) mutants. The tex23‐1/rsp5‐3 mutant, which is complemented by RSP5, not only shows a strong nuclear accumulation of tRNAs at the restrictive temperature, but also is severely impaired in the nuclear export of mRNAs and 60S pre‐ribosomal subunits. In contrast, nuclear localization sequence (NLS)‐mediated nuclear protein import is unaffected in this mutant. Strikingly, the nuclear RNA export defects seen in the rsp5‐3 strain are accompanied by a dramatic inhibition of both rRNA and tRNA processing, a combination of phenotypes that has not been reported for any previously characterized mutation in yeast. These data implicate ubiquitination as a mechanism coordinating the major nuclear RNA biogenesis pathways.