RNA helicase DDX21 mediates nucleotide stress responses in neural crest and melanoma cells

Nat Cell Biol. 2020 Apr;22(4):372-379. doi: 10.1038/s41556-020-0493-0. Epub 2020 Mar 30.


The availability of nucleotides has a direct impact on transcription. The inhibition of dihydroorotate dehydrogenase (DHODH) with leflunomide impacts nucleotide pools by reducing pyrimidine levels. Leflunomide abrogates the effective transcription elongation of genes required for neural crest development and melanoma growth in vivo1. To define the mechanism of action, we undertook an in vivo chemical suppressor screen for restoration of neural crest after leflunomide treatment. Surprisingly, we found that alterations in progesterone and progesterone receptor (Pgr) signalling strongly suppressed leflunomide-mediated neural crest effects in zebrafish. In addition, progesterone bypasses the transcriptional elongation block resulting from Paf complex deficiency, rescuing neural crest defects in ctr9 morphant and paf1(alnz24) mutant embryos. Using proteomics, we found that Pgr binds the RNA helicase protein Ddx21. ddx21-deficient zebrafish show resistance to leflunomide-induced stress. At a molecular level, nucleotide depletion reduced the chromatin occupancy of DDX21 in human A375 melanoma cells. Nucleotide supplementation reversed the gene expression signature and DDX21 occupancy changes prompted by leflunomide. Together, our results show that DDX21 acts as a sensor and mediator of transcription during nucleotide stress.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • DEAD-box RNA Helicases / genetics*
  • DEAD-box RNA Helicases / metabolism
  • Dihydroorotate Dehydrogenase
  • Embryo, Nonmammalian
  • Gene Expression Regulation, Developmental
  • Humans
  • Leflunomide / pharmacology
  • Melanocytes / drug effects
  • Melanocytes / metabolism*
  • Melanocytes / pathology
  • Neural Crest / drug effects
  • Neural Crest / growth & development
  • Neural Crest / metabolism*
  • Nucleotides
  • Oxidoreductases Acting on CH-CH Group Donors / genetics*
  • Oxidoreductases Acting on CH-CH Group Donors / metabolism
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism
  • Progesterone / metabolism
  • Protein Binding
  • Receptors, Progesterone / genetics*
  • Receptors, Progesterone / metabolism
  • Signal Transduction
  • Stress, Physiological / genetics
  • Transcription Elongation, Genetic
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Zebrafish / embryology
  • Zebrafish / genetics
  • Zebrafish / metabolism
  • Zebrafish Proteins / genetics*
  • Zebrafish Proteins / metabolism


  • Dihydroorotate Dehydrogenase
  • Nucleotides
  • Phosphoproteins
  • Receptors, Progesterone
  • Transcription Factors
  • Zebrafish Proteins
  • Progesterone
  • Oxidoreductases Acting on CH-CH Group Donors
  • DDX1 protein, human
  • DEAD-box RNA Helicases
  • ddx21 protein, zebrafish
  • Leflunomide