Survival motor neuron protein in the nucleolus of mammalian neurons.
Spinal muscular atrophy (SMA) is an inherited motor neuron disease caused by mutations in the survival motor neuron gene (SMN1). While it has been shown that the SMN protein is involved in spliceosome biogenesis and pre-mRNA splicing, there is increasing evidence indicating that SMN may also perform important functions in the nucleolus. We demonstrate here through the use of a previously characterized polyclonal anti-SMN antibody, abSMN, that the SMN protein shows a striking colocalization with the nucleolar protein, fibrillarin, in both nucleoli and Cajal bodies/gems of primary neurons. Immunoblot analysis with antifibrillarin and two different anti-SMN antibodies reveals that SMN and fibrillarin also cofractionate in the insoluble protein fraction of cultured cell lysates. Immunoprecipitation experiments using whole cell extracts of HeLa cells and cultured neurons revealed that abSMN coprecipitated small amounts of the U3 small nucleolar RNA (snoRNA) previously shown to be associated with fibrillarin in vivo. These studies raise the possibility that SMN may serve a function in rRNA maturation/ribosome synthesis similar to its role in spliceosome biogenesis.
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA.
Karen A
KA
Wehner
Laura
L
Ayala
Youngseon
Y
Kim
Philip J
PJ
Young
Betsy A
BA
Hosler
Christian L
CL
Lorson
Susan J
SJ
Baserga
Jonathan W
JW
Francis
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000378:metabolism; D002466:Cell Nucleolus / Q000378:metabolism*; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein; D006367:HeLa Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D051379:Mice; D008856:Microscopy, Fluorescence; D009046:Motor Neurons / Q000378:metabolism* / Q000648:ultrastructure; D009134:Muscular Atrophy, Spinal / Q000378:metabolism / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism; D011233:Precipitin Tests; D016601:RNA-Binding Proteins; D011817:Rabbits; D051381:Rats; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism; D055532:SMN Complex Proteins; D055533:Survival of Motor Neuron 1 Protein; D014407:Tumor Cells, Cultured
D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear; D055532:SMN Complex Proteins; C526471:SMN1 protein, human; C526472:Smn1 protein, mouse; C526473:Smn1 protein, rat; D055533:Survival of Motor Neuron 1 Protein