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Splicing factor DHX15 affects tp53 and mdm2 expression via alternate splicing and promoter usage.

Authors
  • McElderry, John1
  • Carrington, Blake1
  • Bishop, Kevin1
  • Kim, Erika2
  • Pei, Wuhong3
  • Chen, Zelin3
  • Ramanagoudr-Bhojappa, Ramanagouda4
  • Prakash, Anupam1
  • Burgess, Shawn M3
  • Liu, P Paul2
  • Sood, Raman1, 2
  • 1 Zebrafish Core, Translational and Functional Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
  • 2 Oncogenesis and Development Section, Translational and Functional Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
  • 3 Developmental Genomics Section, Translational and Functional Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
  • 4 Cancer Genomics Unit, Cancer Genetics and Comparative Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Type
Published Article
Journal
Human Molecular Genetics
Publisher
Oxford University Press
Publication Date
Dec 15, 2019
Volume
28
Issue
24
Pages
4173–4185
Identifiers
DOI: 10.1093/hmg/ddz261
PMID: 31691804
Source
Medline
Language
English
License
Unknown

Abstract

DHX15, a DEAH box containing RNA helicase, is a splicing factor required for the last step of splicing. Recent studies identified a recurrent mutational hotspot, R222G, in DHX15 in ∼ 6% of acute myeloid leukemia (AML) patients that carry the fusion protein RUNX1-RUNX1T1 produced by t (8;21) (q22;q22). Studies using yeast mutants showed that substitution of G for the residue equivalent to R222 leads to loss of its helicase function, suggesting that it is a loss-of-function mutation. To elucidate the role of DHX15 during development, we established the first vertebrate knockout model with CRISPR/Cas9 in zebrafish. Our data showed that dhx15 expression is enriched in the brain, eyes, pectoral fin primordia, liver and intestinal bulb during embryonic development. Dhx15 deficiency leads to pleiotropic morphological phenotypes in homozygous mutant embryos starting at 3 days post fertilization (dpf) that result in lethality by 7 dpf, revealing an essential role during embryonic development. RNA-seq analysis suggested important roles of Dhx15 in chromatin and nucleosome assembly and regulation of the Mdm2-p53 pathway. Interestingly, exons corresponding to the alternate transcriptional start sites for tp53 and mdm2 were preferentially expressed in the mutant embryos, leading to significant upregulation of their alternate isoforms, Δ113p53 (orthologous to Δ133p53 isoform in human) and mdm2-P2 (isoform using distal promoter P2), respectively. We speculate that these alterations in the Mdm2-p53 pathway contribute to the development of AML in patients with t(8;21) and somatically mutated DHX15. Published by Oxford University Press 2019.

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