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

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