Phosphorylation of the homeotic tumor suppressor Cdx2 mediates its ubiquitin-dependent proteasome degradation

Oncogene. 2005 Dec 1;24(54):7955-63. doi: 10.1038/sj.onc.1208945.

Abstract

The Caudal-related homeodomain transcription factor Cdx2 plays a key role in intestinal cell fate determination. Reduction of Cdx2 expression is a feature of many human colon carcinomas and inactivation of one cdx2 allele facilitates the development of invasive adenocarcinoma in the murine colon. Here, we investigated the post-translational regulation of Cdx2. We showed that various forms of Cdx2 coexist in the intestine and colon cancer cell lines, some of them being phosphorylated forms. We found that cyclin-dependent kinase 2 phosphorylated Cdx2 in vitro and in vivo. Using site-specific mutagenesis, we identified serine 281 as a new key residue for Cdx2 phosphorylation. Intriguingly, serine 281 belongs to a conserved motif of four evenly spaced serines (the 4S motif) similar to the one controlling beta-catenin degradation by the proteasome pathway. A nonphosphorylated mutant Cdx2 lacking the 4S motif (4S>A) exhibited reduced polyubiquitination upon proteasome inhibition and increased stability compared to wild-type Cdx2. In addition, we found that this mutant was less efficient to suppress colony formation than wild-type Cdx2. Thus, our data highlight a novel post-translational mechanism controlling Cdx2 degradation via phosphorylation and polyubiquitination, which may be of importance for intestinal development and cancer.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / genetics
  • Adenocarcinoma / pathology
  • Alanine / metabolism
  • Alkaline Phosphatase / antagonists & inhibitors
  • Alkaline Phosphatase / metabolism
  • Alkaline Phosphatase / pharmacology
  • Amino Acid Sequence / genetics
  • Amino Acid Substitution
  • Animals
  • CDX2 Transcription Factor
  • COS Cells
  • Caco-2 Cells
  • Chlorocebus aethiops
  • Colonic Neoplasms / chemistry
  • Colonic Neoplasms / genetics*
  • Colonic Neoplasms / pathology
  • Consensus Sequence / genetics
  • Conserved Sequence / genetics
  • Cyclin-Dependent Kinase 2 / metabolism
  • Enzyme Inhibitors / pharmacology
  • Gene Expression Regulation, Neoplastic
  • Genes, Tumor Suppressor*
  • Glycine / metabolism
  • Homeodomain Proteins / chemistry
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Humans
  • Intestinal Mucosa / drug effects
  • Intestinal Mucosa / metabolism
  • Jejunum / drug effects
  • Jejunum / metabolism
  • Mice
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Phosphorylation
  • Proteasome Endopeptidase Complex / metabolism*
  • Protein Processing, Post-Translational
  • Sequence Homology, Amino Acid
  • Serine / chemistry
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription, Genetic
  • Ubiquitin / metabolism*

Substances

  • CDX2 Transcription Factor
  • CDX2 protein, human
  • Cdx2 protein, mouse
  • Enzyme Inhibitors
  • Homeodomain Proteins
  • Transcription Factors
  • Ubiquitin
  • Serine
  • CDK2 protein, human
  • Cyclin-Dependent Kinase 2
  • Alkaline Phosphatase
  • Proteasome Endopeptidase Complex
  • Alanine
  • Glycine