Phosphorylation of the homeotic tumor suppressor Cdx2 mediates its ubiquitin-dependent proteasome degradation.
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.
Gross
Isabelle
I
Development and Physiopathology of the Intestine and Pancreas, 3, avenue Molière, 67200 Strasbourg, France.
Lhermitte
Benoit
B
Domon-Dell
Claire
C
Duluc
Isabelle
I
Martin
Elisabeth
E
Gaiddon
Christian
C
Kedinger
Michele
M
Freund
Jean-Noël
JN
D000230:Adenocarcinoma / Q000235:genetics / Q000473:pathology; D000409:Alanine / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D000595:Amino Acid Sequence / Q000235:genetics; D019943:Amino Acid Substitution; D000818:Animals; D000071616:CDX2 Transcription Factor; D019556:COS Cells; D018938:Caco-2 Cells; D002522:Chlorocebus aethiops; D003110:Colonic Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D016384:Consensus Sequence / Q000235:genetics; D017124:Conserved Sequence / Q000235:genetics; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D005998:Glycine / Q000378:metabolism; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D025801:Ubiquitin / Q000378:metabolism*
D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; C487514:Cdx2 protein, mouse; D004791:Enzyme Inhibitors; D018398:Homeodomain Proteins; D014157:Transcription Factors; D025801:Ubiquitin; D012694:Serine; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D000469:Alkaline Phosphatase; D046988:Proteasome Endopeptidase Complex; D000409:Alanine; D005998:Glycine