The symplekin/ZONAB complex inhibits intestinal cell differentiation by the repression of AML1/Runx1

Gastroenterology. 2009 Jul;137(1):156-64, 164.e1-3. doi: 10.1053/j.gastro.2009.03.037. Epub 2009 Mar 27.

Abstract

Background & aims: Symplekin is a ubiquitously expressed protein involved in RNA polyadenylation and transcriptional regulation that localizes at tight junctions in epithelial cells. The association between symplekin and the Y-box transcription factor ZONAB activates proliferation in intestinal and kidney cells. We analyzed symplekin expression in human colonic crypts and investigated its function in differentiation.

Methods: Expression of differentiation markers and transcription factors was assessed in HT29-Cl.16E cells that expressed inducible symplekin short hairpin RNA or were transfected with ZONAB small interfering RNAs. Intestines of AML1(Delta/Delta) mice were stained with alcian blue and analyzed for expression of AML1/Runx1, GAPDH, KLF-4, and Muc-2. Mobility shift and chromatin immunoprecipitation were used to detect AML1 and ZONAB/DbpA binding to promoter regions of the Krüppel-like factor 4 (KLF4) and acute myeloid leukemia-1 (AML1) genes, respectively.

Results: The gradient of nuclear symplekin expression decreased from the proliferative toward the differentiated compartment of colonic crypts; symplekin down-regulation promoted the differentiation of HT29-Cl.16E colorectal carcinoma cells into goblet cells. Down-regulation of symplekin or ZONAB/Dbpa induced de novo expression of the transcription factor AML1/Runx1, thereby increasing the expression of KLF4 and promoting goblet cell differentiation. Furthermore, increased AML1 expression was required for the induction of goblet cell differentiation after symplekin down-regulation. KLF4 expression and goblet cell numbers were reduced in the intestines of AML1(Delta/Delta) mice, confirming the role of AML1 as a promoter of intestinal differentiation in vivo.

Conclusions: Symplekin cooperates with ZONAB to negatively regulate intestinal goblet cell differentiation, acting by repression of AML1 and KLF4.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CCAAT-Enhancer-Binding Proteins / genetics
  • CCAAT-Enhancer-Binding Proteins / metabolism*
  • Cell Differentiation*
  • Cell Proliferation
  • Core Binding Factor Alpha 2 Subunit / genetics
  • Core Binding Factor Alpha 2 Subunit / metabolism*
  • Glyceraldehyde-3-Phosphate Dehydrogenases / metabolism
  • Goblet Cells / enzymology
  • Goblet Cells / metabolism*
  • HT29 Cells
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism*
  • Humans
  • Intestinal Mucosa / metabolism*
  • Intestines / enzymology
  • Kruppel-Like Transcription Factors / metabolism
  • Mice
  • Mice, Transgenic
  • Mucin-2 / metabolism
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • RNA Interference
  • Transfection

Substances

  • CCAAT-Enhancer-Binding Proteins
  • Core Binding Factor Alpha 2 Subunit
  • GKLF protein
  • Heat-Shock Proteins
  • Kruppel-Like Transcription Factors
  • Muc2 protein, mouse
  • Mucin-2
  • Nuclear Proteins
  • RUNX1 protein, human
  • Runx1 protein, mouse
  • SYMPK protein, human
  • YBX3 protein, human
  • Glyceraldehyde-3-Phosphate Dehydrogenases