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Hepatocyte nuclear factor-1[alpha] (HNF-1[alpha]) is a modified homeodomain-containing transcription factor that has been implicated in the regulation of intestinal genes. To define the importance and underlying mechanism of HNF-1[alpha] for the regulation of intestinal gene expression in vivo, we analyzed the expression of the intestinal differentiation markers and putative HNF-1[alpha] targets lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) in hnf1[alpha] null mice. We found that in adult jejunum, LPH mRNA in hnf1[[alpha].sup.-/-] mice was reduced 95% compared with wild-type controls (P < 0.01, n = 4), whereas SI mRNA was virtually identical to that in wild-type mice. Furthermore, SI mRNA abundance was unchanged in the absence of HNF-1[alpha] along the length of the adult mouse small intestine as well as in newborn jejunum. We found that HNF-1[alpha] occupies the promoters of both the LPH and SI genes in vivo. However, in contrast to liver and pancreas, where HNF-1[alpha] regulates target genes by recruitment of histone acetyl transferase activity to the promoter, the histone acetylation state of the LPH and SI promoters was not affected by the presence or absence of HNF-1[alpha]. Finally, we showed that a subset of hypothesized intestinal target genes is regulated by HNF-1[alpha] in vivo and that this regulation occurs in a defined tissue-specific and developmental context. These data indicate that HNF-1[alpha] is an activator of a subset of intestinal genes and induces these genes through an alternative mechanism in which it is dispensable for chromatin remodeling. sucrase-isomaltase; liver fatty acid binding protein; intestinal gene expression; chromatin modification

Complex regulation of the lactase-phlorizin hydrolase promoter by GATA-4. Am J Physiol Gastrointest Liver Physio1287: G899--G3909, 2004. First published June 3, 2004; 10.1152/ajpgi.00150.2004.--Lactase-phlorizin hydrolase (LPH), a marker of intestinal differentiation, is expressed in absorptive enterocytes on small intestinal villi in a tightly regulated pattern along the proximal-distal axis. The LPH promoter contains binding sites that mediate activation by members of the GATA-4, -5, and -6 subfamily, but little is known about their individual contribution to LPH regulation in vivo. Here, we show that GATA-4 is the principal GATA factor from adult mouse intestinal epithelial cells that binds to the mouse LPH promoter, and its expression is highly correlated with that of LPH mRNA in jejunum and ileum. GATA-4 cooperates with hepatocyte nuclear factor (HNF)-1[alpha] to synergistically activate the LPH promoter by a mechanism identical to that previously characterized for GATA-5/HNF-1[alpha], requiring physical association between GATA-4 and HNF-1[alpha] and intact HNF-1 binding sites on the LPH promoter. GATA-4 also activates the LPH promoter independently of HNF-l[alpha], in contrast to GATA-5, which is unable to activate the LPH promoter in the absence of HNF-l[alpha]. GATA-4-specific activation requires intact GATA binding sites on the LPH promoter and was mapped by domain-swapping experiments to the zinc finger and basic regions. However, the difference in the capacity between GATA-4 and GATA-5 to activate the LPH promoter was not due to a difference in affinity for binding to GATA binding sites on the LPH promoter. These data indicate that GATA-4 is a key regulator of LPH gene expression that may function through an evolutionarily conserved mechanism involving cooperativity with an HNF-1[alpha] and/or a GATA-specific pathway independent of HNF-1[alpha]. lactase-phlorizin hydrolase: intestinal differentiation; GATA-4; hepatocyte nuclear factor-1[alpha];

Differential activation of intestinal gene promoters: functional interactions between GATA-5 and HNF-1[Alpha]. Am J Physiol Gastrointest Liver Physiol 281: G69-G84, 2001.--The effects of GATA-4, -5, and -6, hepatocyte nuclear factor-1[Alpha] (HNF-1[Alpha] and -[Beta], and Cdx-2 on the rat and human lactase-phlorizin hydrolase (LPH) and human sucrase-isomaltase (SI) promoters were studied using transient cotransfection assays in Caco-2 cells. GATA factors and HNF-1[Alpha] were strong activators of the LPH promoters, whereas HNF-1[Alpha] and Cdx-2 were strong activators of the SI promoter, although GATA factors were also necessary for maximal activation of the SI gene. Cotransfection of GATA-5 and HNF-1[Alpha] together resulted in a higher activation of all three promoters than the sum of the activation by either factor alone, demonstrating functional cooperativity. In the human LPH promoter, an intact HNF-1 binding site was required for functional synergy. This study is the first to demonstrate 1) differential activation of the LPH and SI promoters by multiple transcription factors cotransfected singly and in combination and 2) that GATA and HNF-1 transcription factors cooperatively activate intestinal gene promoters. Synergistic activation is a mechanism by which higher levels of tissue-specific expression might be attained by overlapping expression of specific transcription factors. lactase-phlorizin hydrolase; sucrase-isomaltase; Cdx-2; hepatocyte nuclear factor-1