Cajal body surveillance of U snRNA export complex assembly.
Phosphorylated adaptor for RNA export (PHAX) is the key export mediator for spliceosomal U small nuclear RNA (snRNA) precursors in metazoa. PHAX is enriched in Cajal bodies (CBs), nuclear subdomains involved in the biogenesis of small ribonucleoproteins. However, CBs' role in U snRNA export has not been demonstrated. In this study, we show that U snRNA precursors microinjected into Xenopus laevis oocyte nuclei temporarily concentrate in CBs but gradually decrease as RNA export proceeds. Inhibition of PHAX activity by the coinjection of a specific anti-PHAX antibody or a dominant-negative PHAX mutant inhibits U snRNA export and simultaneously enhances accumulation of U snRNA precursors in CBs, indicating that U snRNAs transit through CBs before export and that binding to PHAX is required for efficient exit of U snRNAs from CBs. Similar results were obtained with U snRNAs transcribed from microinjected genes. These results reveal a novel function for CBs, which ensure that U snRNA precursors are properly bound by PHAX.
Suzuki
Tatsuya
T
Institute for Virus Research, Kyoto University, Kyoto, Japan.
Izumi
Hiroto
H
Ohno
Mutsuhito
M
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D020541:Coiled Bodies / Q000235:genetics / Q000378:metabolism*; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis; D000097606:Exportin 1 Protein
D028884:Karyopherins; D029543:Nucleocytoplasmic Transport Proteins; D012322:RNA Precursors; D012342:RNA, Small Nuclear; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein; C405487:U7 small nuclear RNA