Intestinal alkaline phosphatase gene expression is activated by ZBP-89

Madhu S. Malo, Moushumi Mozumder, Bo Zhang Xiao, Shaluk Biswas, Alexander Chen, Long Chuan Bai, Juanita L. Merchant, Richard A. Hodin

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Intestinal alkaline phosphatase (IAP) is an enterocyte differentiation marker that functions to limit fat absorption. Zinc finger binding protein-89 (ZBP-89) is a Kruppel-type transcription factor that appears to promote a differentiated phenotype in the intestinal epithelium. The purpose of this study was to investigate the regulation of IAP gene expression by ZBP-89. RT-PCR, quantitative real-time RT-PCR, Western blot analyses, and reporter assays were used to determine the regulation of IAP by ZBP-89 in HT-29 and Caco-2 colon cancer cells. ZBP-89 knockdown was achieved by specific short interfering (si)RNA. EMSA and chromatin immunoprecipitation (ChIP) were performed to examine the binding of ZBP-89 to the IAP promoter. The results of RT-PCR, quantitative real-time PCR, and Western blot analyses showed that ZBP-89 was expressed at low levels in Caco-2 and HT-29 cells, whereas IAP was minimally expressed and absent in these cells, respectively. Transfection with ZBP-89 expression plamid increased IAP mRNA and protein levels in both cell lines, whereas knockdown of endogenous ZBP-89 by siRNA reduced basal levels of IAP gene expression in Caco-2 cells. IAP-luciferase reporter assays, EMSA, and ChIP established that ZBP-89 activated the IAP gene through a response element (ZBP-89 response element: 5′-CCTCCTCCC-3′) located between -1018 and -1010 bp upstream of the AUG start codon. We conclude that ZBP-89 is a direct transcriptional activator of the enterocyte differentiation marker IAP. These findings are consistent with the role that this transcription factor is thought to play as a tumor suppressor and suggests its possible function in the physiology of fat absorption.

Original languageEnglish (US)
Pages (from-to)G737-G746
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume290
Issue number4
DOIs
StatePublished - Apr 2006
Externally publishedYes

Keywords

  • Carcinogenesis
  • Development
  • Enterocyte differentiation
  • Eukaryotic promoter
  • Transient transfection

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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