A U3 snoRNP protein with homology to splicing factor PRP4 and Gβ domains is required for ribosomal RNA processing

R. Jansen*, D. Tollervey, E. C. Hurt

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Yeast fibrillarin (NOP1) is an evolutionarily conserved, nucleolar protein necessary for multiple steps in ribosome biogenesis. Yeast mutants lacking a functional NOP1 gene can be complemented by human Fibrillarin but are temperature sensitive for growth and impaired in pre-rRNA processing. In order to identify components which interact functionally with human Fibrillarin in yeast, we isolated extragenic suppressors of this phenotype. One dominant suppressor, sof1-56, which is allele-specific for human Fibrillarin and restores growth and pre-RNA processing at 35°C, was cloned by in vivo complementation. The wild-type allele of SOF1 is essential for cell growth and encodes a novel 56 kDa protein. In its central domain, SOF1 contains a repeated sequence also found in β-subunits of trimeric G-proteins and the splicing factor PRP4. A single amino acid exchange in the G(β)-like repeat domain is responsible for the suppressing activity of sof1-56. Indirect immunofluorescence shows that SOF1 is located within the yeast nucleolus. Co-immunoprecipitation demonstrates the physical association of SOF1 with U3 small nucleolar RNA and NOP1. In vivo depletion of SOF1 leads to impaired pre-rRNA processing and inhibition of 18S rRNA production. Thus, SOF1 is a new component of the nucleolar rRNA processing machinery.

Original languageEnglish
Pages (from-to)2549-2558
Number of pages10
JournalEMBO Journal
Volume12
Issue number6
Publication statusPublished - 1 Jan 1993

Keywords

  • nucleolus
  • ribosome biogenesis
  • rRNA processing
  • snoRNA

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