MINDY3

MINDY3 is a K48-linked polyubiquitin-preferring deubiquitinase that acts on protein stability and cell-cycle control across multiple cellular contexts [PMID:42006908, PMID:bio_10.1101_2025.07.16.665128]. Its catalytic activity toward long K48-linked polyubiquitin chains is potentiated by an atypical EF-hand domain that doubles as a ubiquitin-binding module with three distinct binding sites; this same domain selectively engages the UBL domains of RAD23A and RAD23B, recruits MINDY3 to DNA damage sites, and assembles a ternary complex with RAD23A/B and polyubiquitin, positioning MINDY3 to deubiquitinate RAD23-bound clients [PMID:bio_10.1101_2025.07.16.665128]. In osteoclasts, MINDY3 is delivered to its substrate RACK1 by the scaffold TTC26, where it removes K48-linked chains to stabilize RACK1 and activate NFATc1-driven osteoclastogenesis (PMID:42006908). Independently, MINDY3 (as C10ORF97) physically associates with JAB1 to block JAB1-mediated nuclear-to-cytoplasmic translocation of p27, producing G1 arrest and suppressing tumor cell growth, migration, and adhesion (PMID:21499297).

1. 2011 Medium

   Before its enzymatic identity was known, MINDY3 (C10ORF97) was placed as a growth suppressor by showing it controls p27 localization, establishing a cell-cycle function for the protein.

   Evidence Co-immunoprecipitation, cell-cycle and proliferation/motility assays, and in vivo tumor suppression in cells

   PMID:21499297

   Open questions at the time

   • Mechanism described as physical association without in vitro reconstitution
   • No link to deubiquitinase activity established at this stage
   • Single-lab finding without reciprocal structural validation of the JAB1 interaction
2. 2025 High

   The structural basis of MINDY3 chain selectivity and recruitment was resolved by showing its EF-hand domain is a three-site ubiquitin-binding module that both enhances cleavage of long K48 chains and specifically binds RAD23A/B UBL domains to target DNA damage sites.

   Evidence Crystal structure of EF-hand:RAD23A UBL complex, in vitro cleavage and UBL-binding specificity panels, and cell-based DNA damage recruitment assays

   PMID:bio_10.1101_2025.07.16.665128

   Open questions at the time

   • Preprint not yet peer-reviewed
   • Direct deubiquitylation of RAD23A/B-bound clients inferred from ternary complex but not demonstrated on physiological substrates
   • Functional consequence of DNA damage recruitment on repair outcomes not measured
3. 2026 Medium

   A physiological substrate and recruitment route were defined by showing TTC26 scaffolds MINDY3 onto RACK1 for K48-linked deubiquitination, linking MINDY3 catalysis to NFATc1-driven osteoclastogenesis.

   Evidence Reciprocal Co-IP, Western blotting, in vitro osteoclast differentiation assays, RNA-seq, and Ttc26 conditional knockout mouse models

   PMID:42006908

   Open questions at the time

   • Full in vitro reconstitution of MINDY3-mediated RACK1 deubiquitination not explicitly established
   • How TTC26 scaffolding relates to EF-hand/RAD23-mediated recruitment is unresolved
   • Single-lab in vivo model

• Whether the distinct functions of MINDY3 — p27/JAB1 cell-cycle control, RAD23-directed DNA damage recruitment, and TTC26/RACK1 osteoclast signaling — represent one unified substrate logic or context-specific adaptor-driven targeting remains unresolved.
• No single study integrates the DNA damage, cell-cycle, and osteoclast roles
• Catalytic dependence of the p27/JAB1 phenotype on deubiquitinase activity untested
• Full complement of physiological MINDY3 substrates undefined