title: IGHMBP2 is a ribosome-associated helicase inactive in the neuromuscular disorder distal SMA type 1 (DSMA1).
abstract: Distal spinal muscular atrophy type 1 (DSMA1) is an autosomal recessive disease that is clinically characterized by distal limb weakness and respiratory distress. In this disease, the degeneration of alpha-motoneurons is caused by mutations in the immunoglobulin mu-binding protein 2 (IGHMBP2). This protein has been implicated in DNA replication, pre-mRNA splicing and transcription, but its precise function in all these processes has remained elusive. We have purified catalytically active recombinant IGHMBP2, which has enabled us to assess its enzymatic properties and to identify its cellular targets. Our data reveal that IGHMBP2 is an ATP-dependent 5' --> 3' helicase, which unwinds RNA and DNA duplices in vitro. Importantly, this helicase localizes predominantly to the cytoplasm of neuronal and non-neuronal cells and associates with ribosomes. DSMA1-causing amino acid substitutions in IGHMBP2 do not affect ribosome binding yet severely impair ATPase and helicase activity. We propose that IGHMBP2 is functionally linked to translation, and that mutations in its helicase domain interfere with this function in DSMA1 patients.
authors.affiliation: Department of Neuropediatrics, Charité University Hospital, Berlin, Germany.
authors.forename: Ulf-Peter
authors.initials: UP
authors.lastname: Guenther
authors.forename: Lusy
authors.initials: L
authors.lastname: Handoko
authors.forename: Bernhard
authors.initials: B
authors.lastname: Laggerbauer
authors.forename: Sibylle
authors.initials: S
authors.lastname: Jablonka
authors.forename: Ashwin
authors.initials: A
authors.lastname: Chari
authors.forename: Mona
authors.initials: M
authors.lastname: Alzheimer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Ohmer
authors.forename: Oliver
authors.initials: O
authors.lastname: Plöttner
authors.forename: Niels
authors.initials: N
authors.lastname: Gehring
authors.forename: Albert
authors.initials: A
authors.lastname: Sickmann
authors.forename: Katja
authors.initials: K
authors.lastname: von Au
authors.forename: Markus
authors.initials: M
authors.lastname: Schuelke
authors.forename: Utz
authors.initials: U
authors.lastname: Fischer
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002457:Cell Extracts; D045744:Cell Line, Tumor; D004265:DNA Helicases / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D051379:Mice; D009134:Muscular Atrophy, Spinal / Q000201:enzymology*; D050505:Mutant Proteins / Q000378:metabolism; D011485:Protein Binding; D012261:Ribonucleoproteins / Q000378:metabolism; D012270:Ribosomes / Q000201:enzymology*; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002457:Cell Extracts; D004268:DNA-Binding Proteins; C489892:IGHMBP2 protein, human; C081225:Ighmbp2 protein, mouse; D050505:Mutant Proteins; D012261:Ribonucleoproteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D004265:DNA Helicases