title: PHAX and CRM1 are required sequentially to transport U3 snoRNA to nucleoli.
abstract: To better understand intranuclear-targeting mechanisms, we have studied the transport of U3 snoRNA in human cells. Surprisingly, we found that PHAX, the snRNA export adaptor, is highly enriched in complexes containing m7G-capped U3 precursors. In contrast, the export receptor CRM1 is predominantly bound to TMG-capped U3 species. In agreement, PHAX does not export m7G-capped U3 precursors because their caps become hypermethylated in the nucleus. Inactivation of PHAX and CRM1 shows that U3 first requires PHAX to reach Cajal bodies, and then CRM1 to be routed from there to nucleoli. Furthermore, PHAX also binds the precursors of U8 and U13 box C/D snoRNAs and telomerase RNA. PHAX was previously shown to discriminate between small versus large RNAs during export. Our data indicate that the role of PHAX in determining the identity of small RNAs extends to nonexported species, and this appears critical to promote their transport within the nucleus.
authors.affiliation: IGMM, CNRS UMR 5535, IFR 122, 34293 Montpellier Cedex 5, France.
authors.forename: Séverine
authors.initials: S
authors.lastname: Boulon
authors.forename: Céline
authors.initials: C
authors.lastname: Verheggen
authors.forename: Beata E
authors.initials: BE
authors.lastname: Jady
authors.forename: Cyrille
authors.initials: C
authors.lastname: Girard
authors.forename: Christina
authors.initials: C
authors.lastname: Pescia
authors.forename: Conception
authors.initials: C
authors.lastname: Paul
authors.forename: Jason K
authors.initials: JK
authors.lastname: Ospina
authors.forename: Tamas
authors.initials: T
authors.lastname: Kiss
authors.forename: A Gregory
authors.initials: AG
authors.lastname: Matera
authors.forename: Rémy
authors.initials: R
authors.lastname: Bordonné
authors.forename: Edouard
authors.initials: E
authors.lastname: Bertrand
mesh_terms: D020816:Amino Acid Motifs; D001692:Biological Transport; D018929:Cell Culture Techniques; D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D020541:Coiled Bodies / Q000378:metabolism; D019175:DNA Methylation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D028884:Karyopherins / Q000502:physiology*; D008856:Microscopy, Fluorescence; D029543:Nucleocytoplasmic Transport Proteins / Q000502:physiology*; D010750:Phosphoproteins / Q000502:physiology*; D010957:Plasmids / Q000378:metabolism; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D020537:RNA, Small Nucleolar / Q000737:chemistry* / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D020718:Ribonucleoproteins, Small Nucleolar / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism; D014162:Transfection; D000097606:Exportin 1 Protein
chemical_list: D049452:Green Fluorescent Proteins; D028884:Karyopherins; D029543:Nucleocytoplasmic Transport Proteins; D010750:Phosphoproteins; D012313:RNA; D020537:RNA, Small Nucleolar; D018160:Receptors, Cytoplasmic and Nuclear; D020718:Ribonucleoproteins, Small Nucleolar; D019098:Telomerase; D000097606:Exportin 1 Protein; C498688:PHAX protein, human; C117378:RNA, U3 small nucleolar; C117377:ribonucleoprotein, U3 small nucleolar