Cryptic out-of-frame translational initiation of TBCE rescues tubulin formation in compound heterozygous HRD

Proc Natl Acad Sci U S A. 2006 Sep 5;103(36):13491-6. doi: 10.1073/pnas.0602798103. Epub 2006 Aug 28.

Abstract

Microtubules are indispensable dynamic structures that contribute to many essential biological functions. Assembly of the native alpha/beta tubulin heterodimer, the subunit that polymerizes to form microtubules, requires the participation of several molecular chaperones, namely prefoldin, the cytosolic chaperonin CCT, and a series of five tubulin-specific chaperones termed cofactors A-E (TBCA-E). Among these, TBCC, TBCD, and TBCE are essential in higher eukaryotes; they function together as a multimolecular machine that assembles quasinative CCT-generated alpha- and beta-tubulin polypeptides into new heterodimers. Deletion and truncation mutations in the gene encoding TBCE have been shown to cause the rare autosomal recessive syndrome known as HRD, a devastating disorder characterized by congenital hypoparathyroidism, mental retardation, facial dysmorphism, and extreme growth failure. Here we identify cryptic translational initiation at each of three out-of-frame AUG codons upstream of the genetic lesion as a unique mechanism that rescues a mutant HRD allele by producing a functional TBCE protein. Our data explain how afflicted individuals, who would otherwise lack the capacity to make functional TBCE, can survive and point to a limiting capacity to fold tubulin heterodimers de novo as a contributing factor to disease pathogenesis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Abnormalities, Multiple / genetics
  • Abnormalities, Multiple / metabolism
  • Abnormalities, Multiple / pathology*
  • Alleles
  • Base Sequence
  • Dimerization
  • Face / abnormalities
  • Gene Deletion
  • Genes, Recessive
  • Heterozygote
  • Humans
  • Hypoparathyroidism / genetics*
  • Intellectual Disability / genetics*
  • Models, Biological
  • Molecular Chaperones / chemistry
  • Molecular Chaperones / genetics*
  • Molecular Chaperones / physiology*
  • Molecular Sequence Data
  • Mutation*
  • Mutation, Missense
  • Protein Biosynthesis
  • Syndrome
  • Tubulin / metabolism*

Substances

  • Molecular Chaperones
  • TBCE protein, human
  • Tubulin