title: Functional analysis in yeast of the Brix protein superfamily involved in the biogenesis of ribosomes.
abstract: An extensive homology search based on the sequence of the yeast protein Brx1p (biogenesis of ribosomes in Xenopus, YOL077c) revealed that it is a member of a superfamily of proteins sharing remarkable sequence similarities. Previous work on Brx1p showed that this protein is involved in the process of ribosome biogenesis [Kaser et al., Biol. Chem. 382 (2001) 1637-1647]. Brx1p is the founding member of one of the five existing eukaryotic subfamilies which are all present in yeast. Four of them are represented by one essential gene each and one family is represented by two closely related genes which can functionally replace each other but are essential together for survival. We created conditional alleles of four of the five genes which allowed us to study the effect of depletion of the respective proteins on the ribosome profiles of the strains. In this study we show that not only Brx1p but also three additional superfamily members, namely YHR088w (Rpf1p), YKR081c (Rpf2p) and the homologous proteins Ssf1p (YHR066w)/Ssf2p (YDR312w) are all involved in the multistep process of the assembly of the large ribosomal subunit. This agrees well with the fact that these three proteins, like Brx1p, are located in the nucleolus. Moreover, all four proteins closely interact functionally, because all four mutants are suppressed by the same multicopy suppressor gene.
authors.affiliation: Institute of Genetics and General Biology, University of Salzburg, 5020, Salzburg, Austria.
authors.forename: Edith
authors.initials: E
authors.lastname: Bogengruber
authors.forename: Peter
authors.initials: P
authors.lastname: Briza
authors.forename: Edith
authors.initials: E
authors.lastname: Doppler
authors.forename: Herbert
authors.initials: H
authors.lastname: Wimmer
authors.forename: Lore
authors.initials: L
authors.lastname: Koller
authors.forename: Franco
authors.initials: F
authors.lastname: Fasiolo
authors.forename: Bruno
authors.initials: B
authors.lastname: Senger
authors.forename: Johannes H
authors.initials: JH
authors.lastname: Hegemann
authors.forename: Michael
authors.initials: M
authors.lastname: Breitenbach
mesh_terms: D002466:Cell Nucleolus / Q000378:metabolism*; D016153:Genes, Suppressor; D001678:Organelle Biogenesis; D010448:Peptide Initiation Factors / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D012269:Ribosomal Proteins / Q000096:biosynthesis* / Q000235:genetics; D012270:Ribosomes / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: C451024:BRX1 protein, S cerevisiae; D010448:Peptide Initiation Factors; D016601:RNA-Binding Proteins; C451023:RPF2 protein, S cerevisiae; D012269:Ribosomal Proteins; C451022:Rpf1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins