title: The SMN protein is a key regulator of nuclear architecture in differentiating neuroblastoma cells.
abstract: The cell nucleus contains two closely related structures, Cajal bodies (CBs) and gems. CBs are the first site of accumulation of newly assembled splicing snRNPs (small nuclear ribonucleoproteins) following their import into the nucleus, before they form their steady-state localization in nuclear splicing speckles. Gems are the nuclear site of accumulation of survival motor neurons (SMNs), an insufficiency of which leads to the inherited neurodegenerative condition, spinal muscular atrophy (SMA). SMN is required in the cytoplasm for the addition of core, Sm, proteins to new snRNPs and is believed to accompany snRNPs to the CB. In most cell lines, gems are indistinguishable from CBs, although the structures are often separate in vivo. The relationship between CBs and gems is not fully understood, but there is evidence that symmetrical dimethylation of arginine residues in the CB protein coilin brings them together in HeLa cells. During neuronal differentiation of the human neuroblastoma cell line SH-SY5Y, CBs and gems increase their colocalization, mimicking changes seen during foetal development. This does not result from alterations in the methylation of coilin, but from increased levels of SMN. Expression of exogenous SMN results in an increased efficiency of snRNP transport to nuclear speckles. This suggests different mechanisms are present in different cell types and in vivo that may be significant for the tissue-specific pathology of SMA.
authors.affiliation: School of Biology, University of St Andrews, Bute Medical Buildings, St Andrews, Fife KY16 9TS, UK.
authors.forename: Allyson K
authors.initials: AK
authors.lastname: Clelland
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Kinnear
authors.forename: Lisa
authors.initials: L
authors.lastname: Oram
authors.forename: Julie
authors.initials: J
authors.lastname: Burza
authors.forename: Judith E
authors.initials: JE
authors.lastname: Sleeman
mesh_terms: D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D020541:Coiled Bodies / Q000378:metabolism; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008845:Microinjections; D009046:Motor Neurons / Q000378:metabolism; D009134:Muscular Atrophy, Spinal / Q000378:metabolism / Q000473:pathology; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids; D021381:Protein Transport / Q000235:genetics; D034741:RNA, Small Interfering / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism; D055532:SMN Complex Proteins / Q000378:metabolism; D055533:Survival of Motor Neuron 1 Protein / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D055517:snRNP Core Proteins / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D017411:Ribonucleoproteins, Small Nuclear; D055532:SMN Complex Proteins; D055533:Survival of Motor Neuron 1 Protein; D055517:snRNP Core Proteins; D049452:Green Fluorescent Proteins; D016650:Fluorescein-5-isothiocyanate