Temperature-sensitive mutations demonstrate roles for yeast fibrillarin in pre-rRNA processing, pre-rRNA methylation, and ribosome assembly

David Tollervey*, Hanna Lehtonen, Ralf Jansen, Hildegard Kern, Eduard C. Hurt

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We have generated temperature-sensitive lethal point mutations in the small nucleolar RNA-associated protein fibrillarin (encoded by the NOP1 gene in yeast) and analyzed their effects on ribosome synthesis. The five alleles tested all prevent synthesis of normal ribosomes, but in dramatically different ways. At the non-permissive temperature, the nop1.2 and nop1.5 alleles prevent synthesis of both 18S and 25S rRNA and all pre-rRNA species except the 35S primary transcript. In contrast, the nop1.3, nop1.4, and nop1.7 alleles do not strongly impair processing. In nop1.3 strains, nucleolar methylation of pre-rRNA is strongly inhibited; late, cytoplasmic methylation of 18S rRNA and tRNA methylation continue. The nop1.4 and nop1.7 alleles result in the synthesis of cytoplasmic 60S ribosomal subunits with strongly aberrant mobilities on sucrose gradients even at the permissive temperature, owing to the impairment of a late step in ribosome assembly. Thus, all major posttranscriptional activities in ribosome synthesis, pre-rRNA processing, pre-rRNA modification, and ribosome assembly are dependent on fibrillarin.

Original languageEnglish
Pages (from-to)443-457
Number of pages15
JournalCell
Volume72
Issue number3
DOIs
Publication statusPublished - 12 Feb 1993

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