title: Rrp12 and the Exportin Crm1 participate in late assembly events in the nucleolus during 40S ribosomal subunit biogenesis.
abstract: During the biogenesis of small ribosomal subunits in eukaryotes, the pre-40S particles formed in the nucleolus are rapidly transported to the cytoplasm. The mechanisms underlying the nuclear export of these particles and its coordination with other biogenesis steps are mostly unknown. Here we show that yeast Rrp12 is required for the exit of pre-40S particles to the cytoplasm and for proper maturation dynamics of upstream 90S pre-ribosomes. Due to this, in vivo elimination of Rrp12 leads to an accumulation of nucleoplasmic 90S to pre-40S transitional particles, abnormal 35S pre-rRNA processing, delayed elimination of processing byproducts, and no export of intermediate pre-40S complexes. The exportin Crm1 is also required for the same pre-ribosome maturation events that involve Rrp12. Thus, in addition to their implication in nuclear export, Rrp12 and Crm1 participate in earlier biosynthetic steps that take place in the nucleolus. Our results indicate that, in the 40S subunit synthesis pathway, the completion of early pre-40S particle assembly, the initiation of byproduct degradation and the priming for nuclear export occur in an integrated manner in late 90S pre-ribosomes.
authors.affiliation: Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer (IBMCC), CSIC-University of Salamanca, Salamanca, Spain.
authors.forename: Giulia
authors.initials: G
authors.lastname: Moriggi
authors.affiliation: Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer (IBMCC), CSIC-University of Salamanca, Salamanca, Spain.
authors.forename: Blanca
authors.initials: B
authors.lastname: Nieto
authors.affiliation: Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer (IBMCC), CSIC-University of Salamanca, Salamanca, Spain; Departamento de Bioquímica y Biología Molecular, University of Salamanca, Salamanca, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Dosil
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000235:genetics; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism*; D028884:Karyopherins / Q000502:physiology*; D009687:Nuclear Proteins / Q000502:physiology*; D030781:Organisms, Genetically Modified; D055503:Protein Multimerization; D021381:Protein Transport / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D000097606:Exportin 1 Protein
chemical_list: D028884:Karyopherins; D009687:Nuclear Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D000097606:Exportin 1 Protein; C481980:Rrp12 protein, S cerevisiae