title: Shutdown of achaete-scute homolog-1 expression by heterogeneous nuclear ribonucleoprotein (hnRNP)-A2/B1 in hypoxia.
abstract: The basic helix-loop-helix transcription factor hASH1, encoded by the ASCL1 gene, plays an important role in neurogenesis and tumor development. Recent findings indicate that local oxygen tension is a critical determinant for the progression of neuroblastomas. Here we investigated the molecular mechanisms underlying the oxygen-dependent expression of hASH1 in neuroblastoma cells. Exposure of human neuroblastoma-derived Kelly cells to 1% O2 significantly decreased ASCL1 mRNA and hASH1 protein levels. Using reporter gene assays, we show that the response of hASH1 to hypoxia is mediated mainly by post-transcriptional inhibition via the ASCL1 mRNA 5'- and 3'-UTRs, whereas additional inhibition of the ASCL1 promoter was observed under prolonged hypoxia. By RNA pulldown experiments followed by MALDI/TOF-MS analysis, we identified heterogeneous nuclear ribonucleoprotein (hnRNP)-A2/B1 and hnRNP-R as interactors binding directly to the ASCL1 mRNA 5'- and 3'-UTRs and influencing its expression. We further demonstrate that hnRNP-A2/B1 is a key positive regulator of ASCL1, findings that were also confirmed by analysis of a large compilation of gene expression data. Our data suggest that a prominent down-regulation of hnRNP-A2/B1 during hypoxia is associated with the post-transcriptional suppression of hASH1 synthesis. This novel post-transcriptional mechanism for regulating hASH1 levels will have important implications in neural cell fate development and disease.
authors.affiliation: Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, D-10117 Berlin.
authors.forename: Mumtaz
authors.initials: M
authors.lastname: Kasim
authors.affiliation: Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, D-10117 Berlin.
authors.forename: Edgar
authors.initials: E
authors.lastname: Benko
authors.affiliation: RNA Editing and Hyperexcitability Disorders Helmholtz Group, Max Delbrück Center for Molecular Medicine, D-13125 Berlin, and.
authors.forename: Aline
authors.initials: A
authors.lastname: Winkelmann
authors.affiliation: Klinik für Innere Medizin III, AG Experimentelle Nephrologie, Universitätsklinikum Jena, D-07743 Jena, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Mrowka
authors.affiliation: Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, D-10117 Berlin.
authors.forename: Jonas J
authors.initials: JJ
authors.lastname: Staudacher
authors.affiliation: Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, D-10117 Berlin.
authors.forename: Pontus B
authors.initials: PB
authors.lastname: Persson
authors.affiliation: Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, D-10117 Berlin.
authors.forename: Holger
authors.initials: H
authors.lastname: Scholz
authors.affiliation: RNA Editing and Hyperexcitability Disorders Helmholtz Group, Max Delbrück Center for Molecular Medicine, D-13125 Berlin, and.
authors.forename: Jochen C
authors.initials: JC
authors.lastname: Meier
authors.affiliation: Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, D-10117 Berlin,. Electronic address: michael.faehling@charite.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Fähling
mesh_terms: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia / Q000235:genetics; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011817:Rabbits; D017208:Rats, Wistar
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D051792:Basic Helix-Loop-Helix Proteins; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D009363:Neoplasm Proteins; C499318:Ascl1 protein, rat; C439768:hnRNP A2
keywords: ASCL1; Gene Expression; Hypoxia; Post-transcriptional Regulation; RNA Turnover; RNA-binding Protein; hASH1 (Mash1); hnRNP-A2/B1; hnRNP-R