DDX31

DDX31 is a nucleolar DEAD-box helicase that functions in ribosome biogenesis and, in cancer contexts, as a cytoplasmic signaling scaffold. In the nucleolus, DDX31 complexes with nucleophosmin (NPM1) to support pre-rRNA biogenesis; its depletion causes NPM1 translocation to the nucleoplasm where NPM1 sequesters HDM2, stabilizing p53 and triggering G1 arrest and apoptosis (PMID:23019224). When mislocalized to the cytoplasm—as occurs in advanced bladder cancer—DDX31 binds EGFR, phospho-nucleolin, and AKT, serving as a scaffold that activates EGFR–AKT signaling, a function enhanced by gain-of-function p53 transactivation-domain mutants (PMID:29440146, PMID:36977662). DDX31 protein levels are controlled by TRIM25-mediated K63-linked polyubiquitination and proteasomal degradation downstream of TBC1D14, linking ubiquitin-dependent turnover of DDX31 to regulation of rRNA transcription and metastatic capacity (PMID:40784392).

1. 2002 Medium

   Establishing DDX31 as a nucleolar protein resolved where the gene product resides, directing subsequent functional studies toward ribosome biogenesis.

   Evidence Mass spectrometry-based nucleolar proteomics of HeLa cells

   PMID:12429849

   Open questions at the time

   • No functional role established; localization alone does not prove function
   • Single cell line (HeLa) examined
2. 2003 Low

   Classification of DDX31 within the DEAD-box RNA helicase family provided a molecular activity prediction but no direct enzymatic demonstration.

   Evidence Bioinformatic motif analysis across human genome

   PMID:12782131

   Open questions at the time

   • No biochemical demonstration of helicase or ATPase activity
   • Sequence homology alone does not confirm RNA substrate specificity
3. 2012 High

   Two advances established DDX31's molecular interactions: UV-crosslinking identified it as a bona fide mRNA-binding protein, while Co-IP and functional studies in RCC cells demonstrated a DDX31–NPM1 nucleolar complex required for pre-rRNA biogenesis, linking DDX31 depletion to NPM1 relocalization, HDM2 sequestration, p53 stabilization, and growth arrest.

   Evidence UV crosslinking/oligo(dT) interactome capture (HeLa); Co-IP, imaging, RNAi, overexpression, pre-rRNA and cell-cycle assays (RCC cells)

   PMID:22658674 PMID:22681889 PMID:23019224

   Open questions at the time

   • Direct RNA substrates (rRNA vs mRNA) not resolved
   • Helicase enzymatic activity still not demonstrated biochemically
   • Whether p53-dependent growth arrest is the sole consequence of DDX31 loss is untested
4. 2018 High

   Discovery that cytoplasmic DDX31 scaffolds an EGFR–nucleolin complex to activate AKT signaling in advanced bladder cancer revealed a localization-dependent oncogenic function distinct from its nucleolar ribosome biogenesis role.

   Evidence Co-IP, subcellular fractionation, RNAi, in vivo tumor models in MIBC cells

   PMID:29440146

   Open questions at the time

   • Mechanism driving DDX31 nucleolar-to-cytoplasmic redistribution in cancer progression unknown
   • Whether DDX31 helicase activity is required for EGFR–AKT scaffolding not tested
5. 2023 Medium

   Identification of DDX31 as the bridge between EGFR and AKT in the context of gain-of-function p53 TAD mutants explained how mutant p53 enhances EGFR signaling and generalized the cytoplasmic scaffold function beyond bladder cancer.

   Evidence Co-IP demonstrating ternary EGFR–DDX31–AKT complex, subcellular fractionation, multi-tissue analysis

   PMID:36977662

   Open questions at the time

   • Single study; independent replication in additional systems needed
   • Structural basis of DDX31-mediated bridging of EGFR and AKT unknown
6. 2025 Medium

   Elucidation of DDX31 protein turnover via TRIM25-mediated K63-linked polyubiquitination downstream of TBC1D14 connected DDX31 abundance control to ribosome biogenesis regulation and metastatic suppression.

   Evidence Ubiquitination assays identifying E3 ligase and linkage type, Co-IP, in vivo metastasis models in HNSCC

   PMID:40784392

   Open questions at the time

   • K63-linked ubiquitination typically signals non-degradative fates; mechanism linking K63 chains to proteasomal degradation not clarified
   • Whether TRIM25 regulation of DDX31 occurs in non-cancer contexts unknown

• The intrinsic RNA helicase/ATPase activity of DDX31 has never been reconstituted in vitro, so whether its DEAD-box enzymatic function is required for ribosome biogenesis or EGFR scaffolding remains an open question.
• No in vitro helicase or ATPase assay reported
• Direct RNA substrates (specific rRNA precursors or mRNAs) not identified
• No structural information available for DDX31