Hypoxia regulates alternative splicing of HIF and non-HIF target genes.

Abstract

UNLABELLED:

Hypoxia is a common characteristic of many solid tumors. The hypoxic microenvironment stabilizes hypoxia-inducible transcription factor 1α (HIF1α) and 2α (HIF2α/EPAS1) to activate gene transcription, which promotes tumor cell survival. The majority of human genes are alternatively spliced, producing RNA isoforms that code for functionally distinct proteins. Thus, an effective hypoxia response requires increased HIF target gene expression as well as proper RNA splicing of these HIF-dependent transcripts. However, it is unclear if and how hypoxia regulates RNA splicing of HIF targets. This study determined the effects of hypoxia on alternative splicing (AS) of HIF and non-HIF target genes in hepatocellular carcinoma cells and characterized the role of HIF in regulating AS of HIF-induced genes. The results indicate that hypoxia generally promotes exon inclusion for hypoxia-induced, but reduces exon inclusion for hypoxia-reduced genes. Mechanistically, HIF activity, but not hypoxia per se is found to be necessary and sufficient to increase exon inclusion of several HIF targets, including pyruvate dehydrogenase kinase 1 (PDK1). PDK1 splicing reporters confirm that transcriptional activation by HIF is sufficient to increase exon inclusion of PDK1 splicing reporter. In contrast, transcriptional activation of a PDK1 minigene by other transcription factors in the absence of endogenous HIF target gene activation fails to alter PDK1 RNA splicing.

IMPLICATIONS:

This study demonstrates a novel function of HIF in regulating RNA splicing of HIF target genes.

• Authors: Johnny A Sena, Liyi Wang, Lynn E Heasley, Cheng-Jun Hu
• Journal: Molecular cancer research : MCR (Mol Cancer Res) Vol. 12 Issue 9 Pg. 1233-43 (Sep 2014) ISSN: 1557-3125 [Electronic] United States
• PMID: 24850901 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: ©2014 American Association for Cancer Research.

Chemical References

• Basic Helix-Loop-Helix Transcription Factors
• HIF1A protein, human
• Hypoxia-Inducible Factor 1, alpha Subunit
• PDK1 protein, human
• Pyruvate Dehydrogenase Acetyl-Transferring Kinase
• endothelial PAS domain-containing protein 1
• Protein Serine-Threonine Kinases

Topics

• Alternative Splicing (genetics)
• Basic Helix-Loop-Helix Transcription Factors (genetics, metabolism)
• Cell Hypoxia (genetics)
• Cell Line, Tumor
• Cell Survival
• Exons
• Gene Expression Regulation, Neoplastic
• Humans
• Hypoxia-Inducible Factor 1, alpha Subunit (genetics)
• Protein Serine-Threonine Kinases (genetics, metabolism)
• Pyruvate Dehydrogenase Acetyl-Transferring Kinase
• RNA Splicing (genetics)
• Transcriptional Activation (genetics)