The histidine triad protein Hint1 interacts with Pontin and Reptin and inhibits TCF-beta-catenin-mediated transcription

J Cell Sci. 2005 Jul 15;118(Pt 14):3117-29. doi: 10.1242/jcs.02437.

Abstract

Pontin and Reptin previously were identified as nuclear beta-catenin interaction partners that antagonistically modulate beta-catenin transcriptional activity. In this study, Hint1/PKCI, a member of the evolutionary conserved family of histidine triad proteins, was characterised as a new interaction partner of Pontin and Reptin. Pull-down assays and co-immunoprecipitation experiments show that Hint1/PKCI directly binds to Pontin and Reptin. The Hint1/PKCI-binding site was mapped to amino acids 214-295 and 218-289 in Pontin and Reptin, respectively. Conversely, Pontin and Reptin bind to the N-terminus of Hint1/PKCI. Moreover, by its interaction with Pontin and Reptin, Hint1/PKCI is associated with the LEF-1/TCF-beta-catenin transcription complex. In this context, Hint1/PKCI acts as a negative regulator of TCF-beta-catenin transcriptional activity in Wnt-transfected cells and in SW480 colon carcinoma cells as shown in reporter gene assays. Consistent with these observations, Hint1/PKCI represses expression of the endogenous target genes cyclin D1 and axin2 whereas knockdown of Hint1/PKCI by RNA interference increases their expression. Disruption of the Pontin/Reptin complex appears to mediate this modulatory effect of Hint1/PKCI on TCF-beta-catenin-mediated transcription. These data now provide a molecular mechanism to explain the tumor suppressor function of Hint1/PKCI recently suggested from the analysis of Hint1/PKCI knockout mice.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Blotting, Western
  • Cell Line, Tumor
  • Cyclin D1 / antagonists & inhibitors
  • Cyclin D1 / biosynthesis
  • DNA Helicases / metabolism*
  • HeLa Cells
  • Humans
  • Mice
  • Molecular Sequence Data
  • NIH 3T3 Cells
  • Nerve Tissue Proteins / metabolism*
  • TCF Transcription Factors / antagonists & inhibitors*
  • TCF Transcription Factors / metabolism
  • Trans-Activators / metabolism
  • Transcription Factors / metabolism*
  • Transcriptional Activation
  • Transfection
  • beta Catenin / antagonists & inhibitors*
  • beta Catenin / metabolism

Substances

  • HINT1 protein, human
  • Nerve Tissue Proteins
  • TCF Transcription Factors
  • Trans-Activators
  • Transcription Factors
  • beta Catenin
  • Cyclin D1
  • DNA Helicases