Abstract
The mouse sucrase-isomaltase (SI) gene is an enterocyte-specific gene expressed in a complex developmental pattern. We previously reported that a short, evolutionarily conserved gene promoter regulates developmental expression of SI in mouse small intestine. Herein, we investigated the role of a hepatocyte nuclear factor-1 (HNF-1) cis-acting element to regulate SI gene expression in vivo. Transgenic SI gene constructs with a mutated HNF-1 element (SIF3) revealed a strong reduction in promoter activity in comparison with a wild-type construct in mice and during Caco-2 cell differentiation. Nuclear proteins isolated from enterocytes showed increased binding of the HNF-1 alpha complex with a concomitant decrease in the HNF-1 beta-containing complex to the SIF3 element both during the suckling-weaning developmental transition and Caco-2 cell differentiation. These changes coincided with a strong induction of SI gene transcription. In transfection experiments, HNF-1 alpha activated the SI promoter via the SIF3 element, and co-expression of HNF-1 beta impaired this transcriptional activation. These findings demonstrate the essential role of the HNF-1 regulatory element to support SI gene transcription in vivo and suggest that the ratio of HNF-1 alpha to HNF-1 beta plays a role in the transcriptional activity of this gene during intestinal development.
Highlights
Sucrase-isomaltase (SI)1 is an intestine-specific gene that is expressed in complex patterns in epithelial cells during development along the cephalocaudal and the crypt-villus axis of the intestine [1,2,3]
hepatocyte nuclear factor-1 (HNF-1)␣ activated the SI promoter via the SIF3 element, and coexpression of HNF-1 impaired this transcriptional activation. These findings demonstrate the essential role of the HNF-1 regulatory element to support SI gene transcription in vivo and suggest that the ratio of HNF-1␣ to HNF-1 plays a role in the transcriptional activity of this gene during intestinal development
The Ratio of HNF-1 to HNF-1␣ Regulates SI Promoter Activity in Caco-2 Cells——We evaluated whether changes in the relative levels of HNF-1 isoforms have a functional effect on the regulation of SI gene transcription
Summary
Sucrase-isomaltase (SI)1 is an intestine-specific gene that is expressed in complex patterns in epithelial cells during development along the cephalocaudal and the crypt-villus axis of the intestine [1,2,3]. Transgenic SI gene constructs with a mutated HNF-1 element (SIF3) revealed a strong reduction in promoter activity in comparison with a wild-type construct in mice and during Caco-2 cell differentiation. Nuclear proteins isolated from enterocytes showed increased binding of the HNF-1␣ complex with a concomitant decrease in the HNF-1-containing complex to the SIF3 element both during the sucklingweaning developmental transition and Caco-2 cell differentiation.
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