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: Mumtaz Kasim, Edgar Benko, Aline Winkelmann, Ralf Mrowka, Jonas J Staudacher, Pontus B Persson, Holger Scholz, Jochen C Meier, Michael Fähling
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 289 Issue 39 Pg. 26973-26988 (Sep 26 2014) ISSN: 1083-351X [Electronic] United States
• PMID: 25124043 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• 3' Untranslated Regions
• 5' Untranslated Regions
• Ascl1 protein, rat
• Basic Helix-Loop-Helix Transcription Factors
• Heterogeneous-Nuclear Ribonucleoprotein Group A-B
• Neoplasm Proteins
• hnRNP A2

Topics

• 3' Untranslated Regions
• 5' Untranslated Regions
• Animals
• Basic Helix-Loop-Helix Transcription Factors (genetics, metabolism)
• Cell Hypoxia (genetics)
• Cell Line, Tumor
• Gene Expression Regulation, Neoplastic
• Heterogeneous-Nuclear Ribonucleoprotein Group A-B (biosynthesis, genetics)
• Humans
• Neoplasm Proteins (genetics, metabolism)
• Neuroblastoma (genetics, metabolism)
• Promoter Regions, Genetic
• Rabbits
• Rats, Wistar