title: Direct interaction of the spinal muscular atrophy disease protein SMN with the small nucleolar RNA-associated protein fibrillarin.
abstract: Disruption of the survival motor neuron (SMN) gene leads to selective loss of spinal motor neurons, resulting in the fatal human neurodegenerative disorder spinal muscular atrophy (SMA). SMN has been shown to function in spliceosomal small nuclear ribonucleoprotein (snRNP) biogenesis and pre-mRNA splicing. We have demonstrated that SMN also interacts with fibrillarin, a highly conserved nucleolar protein that is associated with all Box C/D small nucleolar RNAs and functions in processing and modification of rRNA. Fibrillarin and SMN co-immunoprecipitate from HeLa cell extracts indicating that the proteins exist as a complex in vivo. Furthermore, in vitro binding studies indicate that the interaction between SMN and fibrillarin is direct and salt-stable. We show that the glycine/arginine-rich domain of fibrillarin is necessary and sufficient for SMN binding and that the region of SMN encoded by exon 3, including the Tudor domain, mediates the binding of fibrillarin. Tudor domain missense mutations, including one found in an SMA patient, impair the interaction between SMN and fibrillarin (as well as the common snRNP protein SmB). Our results suggest a function for SMN in small nucleolar RNP biogenesis (akin to its known role as an snRNP assembly factor) and reveal a potential link between small nucleolar RNP biogenesis and SMA.
authors.affiliation: Department of Biochemistry, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: K W
authors.initials: KW
authors.lastname: Jones
authors.forename: K
authors.initials: K
authors.lastname: Gorzynski
authors.forename: C M
authors.initials: CM
authors.lastname: Hales
authors.forename: U
authors.initials: U
authors.lastname: Fischer
authors.forename: F
authors.initials: F
authors.lastname: Badbanchi
authors.forename: R M
authors.initials: RM
authors.lastname: Terns
authors.forename: M P
authors.initials: MP
authors.lastname: Terns
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000737:chemistry; D002466:Cell Nucleolus / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein; D018076:DNA, Complementary / Q000378:metabolism; D005091:Exons; D015723:Gene Library; D005998:Glycine / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; D020798:Two-Hybrid System Techniques; D014981:Xenopus
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D017362:Cyclic AMP Response Element-Binding Protein; D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; C047458:fibrillarin; D001120:Arginine; D005998:Glycine