Different targets for the fragile X-related proteins revealed by their distinct nuclear localizations.
Fragile X syndrome is caused by the absence of the fragile X mental retardation protein (FMRP). FMRP and its structural homologues FXR1P and FXR2P form a family of RNA-binding proteins (FXR proteins). The three proteins associate with polyribosomes as cytoplasmic mRNP particles. Here we show that small amounts of FMRP, FXR1P and FXR2P shuttle between cytoplasm and nucleus. Mutant FMRP of a severely affected fragile X patient (FMRPI304N) does not associate with polyribosomes and shuttles more frequently than normal FMRP, indicating that the association with polyribosomes regulates the shuttling process. Using leptomycin B we demonstrate that transport of the FXR proteins out of the nucleus is mediated by the export receptor exportin1. Finally, inactivation of the nuclear export signal in two FXR proteins shows that FMRP shuttles between cytoplasm and nucleoplasm, while FXR2P shuttles between cytoplasm and nucleolus. Therefore, molecular dissection of the shuttling routes used by the FXR proteins suggests that they transport different RNAs.
Tamanini
F
F
Department of Clinical Genetics and Center for Biomedical Genetics, Erasmus University, PO Box 1738, 3000 DR Rotterdam, The Netherlands.
Bontekoe
C
C
Bakker
C E
CE
van Unen
L
L
Anar
B
B
Willemsen
R
R
Yoshida
M
M
Galjaard
H
H
Oostra
B A
BA
Hoogeveen
A T
AT
D018829:Adhesins, Bacterial / Q000494:pharmacology; D000818:Animals; D001216:Asparagine; D019556:COS Cells / Q000187:drug effects / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm; D051860:Fragile X Messenger Ribonucleoprotein 1; D005600:Fragile X Syndrome / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007532:Isoleucine; D028884:Karyopherins; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics; D016601:RNA-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear; D014158:Transcription, Genetic; D000097606:Exportin 1 Protein
D018829:Adhesins, Bacterial; D001216:Asparagine; D002352:Carrier Proteins; D051860:Fragile X Messenger Ribonucleoprotein 1; D007532:Isoleucine; D028884:Karyopherins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein; C497683:FMR1 protein, human; C096916:FXR1 protein, human; C096915:FXR2 protein, human