PHAX and CRM1 are required sequentially to transport U3 snoRNA to nucleoli.
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.
Boulon
Séverine
S
IGMM, CNRS UMR 5535, IFR 122, 34293 Montpellier Cedex 5, France.
Verheggen
Céline
C
Jady
Beata E
BE
Girard
Cyrille
C
Pescia
Christina
C
Paul
Conception
C
Ospina
Jason K
JK
Kiss
Tamas
T
Matera
A Gregory
AG
Bordonné
Rémy
R
Bertrand
Edouard
E
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
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