TRIM37 defective in mulibrey nanism is a novel RING finger ubiquitin E3 ligase

Exp Cell Res. 2005 Aug 1;308(1):146-55. doi: 10.1016/j.yexcr.2005.04.001.

Abstract

Mulibrey nanism is an autosomal recessive prenatal-onset growth disorder characterized by dysmorphic features, cardiomyopathy, and hepatomegaly. Mutations in TRIM37 encoding a tripartite motif (TRIM, RING-B-box-coiled-coil)-family protein underlie mulibrey nanism. We investigated the ubiquitin ligase activity predicted for the RING domain of TRIM37 by analyzing its autoubiquitination. Full-length TRIM37 and its TRIM domain were highly polyubiquitinated when co-expressed with ubiquitin. Polyubiquitination was decreased in a mutant protein with disrupted RING domain (Cys35Ser;Cys36Ser) and in the Leu76Pro mutant protein, a disease-associated missense mutation affecting the TRIM domain of TRIM37. Bacterially produced GST-TRIM domain fusion protein, but not its Cys35Ser;Cys36Ser or Leu76Pro mutants, were polyubiquitinated in cell-free conditions, implying RING-dependent modification. Ubiquitin was also identified as an interaction partner for TRIM37 in a yeast two-hybrid screen. Ectopically expressed TRIM37 rapidly formed aggregates that were ubiquitin-, proteasome subunit-, and chaperone-positive in immunofluorescence analysis, defining them as aggresomes. The Cys35Ser;Cys36Ser mutant and the Leu76Pro and Gly322Val patient mutant proteins were markedly less prone to aggregation, implying that aggresomal targeting reflects a physiological function of TRIM37. These findings suggest that TRIM37 acts as a TRIM domain-dependent E3 ubiquitin ligase and imply defective ubiquitin-dependent degradation of an as-yet-unidentified target protein in the pathogenesis of mulibrey nanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Dwarfism / genetics*
  • Gene Expression Regulation
  • Humans
  • Macromolecular Substances / chemistry
  • Macromolecular Substances / metabolism
  • Mutagenesis, Site-Directed
  • Mutation
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism
  • Solubility
  • Ubiquitin / metabolism
  • Ubiquitin-Protein Ligases / genetics*
  • Ubiquitin-Protein Ligases / metabolism
  • Zinc Fingers / genetics*

Substances

  • Macromolecular Substances
  • Nuclear Proteins
  • Ubiquitin
  • TRIM37 protein, human
  • Ubiquitin-Protein Ligases