Cloning and initial characterization of the promoter region of the rat cysteine-rich intestinal protein gene

Copper Alters the Conformation and Transcriptional Activity of the Tumor Suppressor Protein p53 in Human Hep G2 Cells

The tumor suppressor protein p53 plays a role in the molecular response to DNA damage by acting as a DNA-binding transcription factor that regulates specific target genes to arrest the cell cycle, induce repair mechanisms, and initiate apoptotic cell death. To test the effect of copper on the transcriptional activity of p53, Hep G2 cells were transiently transfected with a luciferase reporter gene downstream from multiple p53 response elements. Co-transfection with the p53 gene resulted in a 6-fold increase in luciferase activity, showing that p53 acts as a transcription factor in this system. However, in the presence of copper, luciferase activity was significantly reduced. Oligonucleotide arrays representing 145 known p53-associated genes were hybridized with biotinylated cDNAs from mRNA extracted from control and copper-treated Hep G2 cells. Among the genes that were differentially regulated were fos, RB1, glutathione peroxidase, TGF-β, and 15-lipoxygenase, a gene known to be activated by mutant p53. Although control Hep G2 cells synthesize wild-type p53, immunocytochemistry identified not only wild type, but also mutant p53 in the presence of copper and other agents that induce oxidative damage. Thus, this report not only identifies genes that may play a role in copper-mediated apoptosis, but also suggests that copper-induced oxidative processes result in the synthesis of mutant p53 with altered transcriptional properties.

CRIP1, a novel immune-related protein, activated by Enterococcus faecalis in porcine gastrointestinal epithelial cells

Cysteine-rich intestinal protein 1 (CRIP1) is an important transcriptional regulation factor during the tumor development. Although it was largely studied in the human or mouse, no report has provided functional evidence for it in the swine. To date, the real sequence of porcine CRIP1 (poCRIP1) was also still unknown. In this study, clear characteristics for the poCRIP1 were represented. A 552bp poCRIP1 cDNA was obtained from porcine brain tissue using real time reverse transcriptase PCR. The poCRIP1 showed 89% and 93% homologous with human and cattle, respectively. And it also contained one conserved domain, LIM-CRIP domain. Meanwhile, the genomic structure and promoter map was done and several conserved transcriptional regulatory sites were also predicted in this study. The expression pattern of poCRIP1 indicated that poCRIP1 is expressed in mucosal tissue. An infection experiment about the gut was designed to analyze whether or not poCRIP1 was functional in gut immunity, and an interesting result was that poCRIP1 was only activated by an opportunistic pathogen, Enterococcus faecalis FA2-2. It was the first report to identify the full-length sequence of poCRIP1 gene, represent a clear characteristic and immunologic role of CRIP1 in domestic animal until now.

Rapid induction of GATA transcription factors in developing mouse intestine following glucocorticoid administration

In the developing intestine, transcription of alpha-glucosidase genes such as sucrase-isomaltase and trehalase is stimulated by glucocorticoid administration. The consequent increase of their respective mRNAs is characterized by a 12-h lag, suggesting that the response to glucocorticoids represents a secondary effect. We hypothesized that the primary response of the tissue to glucocorticoids includes induction of one or more intestinal transcription factors. To investigate this hypothesis, we identified a region in the mouse trehalase promoter (located at nucleotides -406 to -377 from the transcription start site) with potential binding sites for three transcription factors: Cdx-2, GATA, and C/EBP. Gel shifts were performed using labeled oligonucleotides from this region with nuclear extracts from jejunums of either control 8-day-old mouse pups or littermates treated with dexamethasone (DEX) 4 h before death. A specific shifted band was observed with DEX extracts but not with control extracts. Supershift assays indicated the presence of GATA-4 and GATA-6 but not GATA-5 nor Cdx-2, C/EBP alpha, C/EBP beta, or C/EBP delta. GATA binding was further implicated by competition studies with mutated oligonucleotides. Finally, Western blot analysis showed GATA-4 and GATA-6 proteins in DEX but not control nuclear extracts. For GATA-4, the same pattern was demonstrated with whole cell extracts and with the cytosol fraction. We conclude that expression of GATA-4 and GATA-6 proteins in the suckling mouse jejunum is stimulated by DEX. This novel finding constitutes an important first step in understanding the molecular mechanism of glucocorticoid action on the developing intestine.

Overexpression of CRIP in transgenic mice alters cytokine patterns and the immune response

Cysteine-rich intestinal protein (CRIP), which contains a double zinc finger motif, is a member of the Group 2 LIM protein family. Our results showed that the developmental regulation of CRIP in neonates was not influenced by conventional vs. specific pathogen-free housing conditions. Thymic and splenic CRIP expression was not developmentally regulated. A line of transgenic (Tg) mice that overexpress the rat CRIP gene was created. When challenged with lipopolysaccharide, the Tg mice lost more weight, exhibited increased mortality, experienced greater diarrhea incidence, and had less serum interferon-gamma (IFN-gamma) and more interleukin (IL)-6 and IL-10. Similarly, splenocytes from the Tg mice produced less IFN-gamma and IL-2 and more IL-10 and IL-6 upon mitogen stimulation. Delayed-type hypersensitivity response was less in the Tg mice. Influenza virus infection produced greater weight loss in the Tg mice, which also showed delayed viral clearance. The observed responses to overexpression of the CRIP gene are consistent with a role for this LIM protein in a cellular pathway that produces an imbalance in cytokine pattern favoring Th2 cytokines.

Bile acids regulate the ontogenic expression of ileal bile acid binding protein in the rat via the farnesoid X receptor

BACKGROUND & AIMS

In the rat, an increase in ileal bile acid binding protein (IBABP) expression occurs during the third postnatal week. In vitro studies suggest that bile acids (BAs) increase IBABP transcription by activating the BA receptor, farnesoid X receptor (FXR). Thus, we investigated the role of BAs on the ontogenic expression of IBABP and whether FXR may mediate these effects.

METHODS

Suckling rats were gavage-fed taurocholate for 3 days or were allowed to develop normally. Ileums were collected for Northern and Western blot analyses. Electrophoretic mobility shift assays for functional FXR were performed using nuclear extracts from ileums of both adult and developing rats.

RESULTS

Taurocholate gavage significantly elevated IBABP messenger RNA and protein levels in suckling animals. Gelshift assays using adult ileal nuclear extracts incubated with a radiolabeled consensus inverted repeat-1 oligonucleotide (response element for FXR) revealed a high-molecular weight DNA/protein complex. Cold competition and supershift assays showed that this complex is sequence specific and confirmed that FXR is a component of the complex. Gelshift assays with nuclear extracts from rat ileum at different ages revealed absence of the DNA/protein complex in the second postnatal week when there is lack of IBABP expression and presence of these complexes at later ages when there is normally high expression. Western blot analyses showed FXR and its heterodimer partner, retinoid X receptor alpha, protein levels are low in the ileum during the suckling period and increase during the third postnatal week.

CONCLUSIONS

BAs play a role in the normal developmental expression of IBABP through FXR activation, and decreased functional FXR in ileal nuclei during the suckling period may account, in part, for the lack of IBABP expression at this time.

Regulation of cysteine-rich intestinal protein, a zinc finger protein, by mediators of the immune response

Cysteine-rich intestinal protein (CRIP), a member of the LIM protein family, has a unique double zinc finger motif as the defining feature. CRIP is highly expressed in intestine and immune cells. CRIP transgenic (Tg) mice and nontransgenic controls were challenged with lipopolysaccharide (LPS). Serum concentrations of interferon-gamma and tumor necrosis factor-alpha were less while those of interleukin-6 and -10 were greater in the Tg mice following LPS administration. CRIP-overexpressing splenocytes produce the same cytokine profile. These responses are consistent with a regulatory role for this protein in cell differentiation, which produces an imbalance in Th1 and Th2 cytokines. Stimulation of CRIP protein levels by LPS is eliminated in metallothionein knockout mice, suggesting metallothionein is the source of zinc for this zinc finger protein and, further, that this could reflect a relationship to the zinc nutritional status and to the aberrant Th1/Th2 cytokine balance observed in zinc deficiency.

Effects of exogenous zinc supplementation on intestinal epithelial repair in vitro

BACKGROUND

Substitution of zinc modulates antioxidant capabilities within the intestinal mucosa and improves intestinal wound healing in zinc-deficient patients with inflammatory bowel diseases. The aim of this study was to characterize the modulating effects of zinc on intestinal epithelial cell function in vitro.

MATERIALS AND METHODS

The effects of zinc on intestinal epithelial cell morphology were assessed by phase contrast and transmission electron microscopy using the non-transformed small intestinal epithelial cell line IEC-6. Zinc-induced apoptosis was assessed by DNA fragmentation analysis, lactate dehydrogluase (LDH) release and flow cytometry with propidium iodine staining. Furthermore, the effects of zinc on IEC-6 cell proliferation were assessed using a colorimetric thiazolyl blue (MTT) assay and on IEC-6 cell restitution using an in vitro wounding model.

RESULTS

Physiological concentrations of zinc (25 microM) did not significantly alter the morphological appearance of IEC-6 cells. However, a 10-fold higher dose of zinc (250 microM) induced epithelial cell rounding, loss of adherence and apoptotic characteristics. While physiological zinc concentrations (< 100 microM) did not induce apoptosis, supraphysiological zinc concentrations (> 100 microM) caused apoptosis. Physiological concentrations of zinc (6.25-50 microM) had no significant effect on intestinal epithelial cell proliferation. In contrast, physiological concentrations of zinc (12.5-50 microM) significantly enhanced epithelial cell restitution through a transforming growth factor-beta (TGFbeta)-independent mechanism. Simultaneous addition of TGFbeta and zinc resulted in an additive stimulation of IEC-6 cell restitution.

CONCLUSION

Zinc may promote intestinal epithelial wound healing by enhancement of epithelial cell restitution, the initial step of epithelial wound healing. Zinc supplementation may improve epithelial repair; however, excessive amounts of zinc may cause tissue injury and impair epithelial wound healing.

Structural characterization of the rat cysteine-rich intestinal protein gene and overexpression of this LIM-only protein in transgenic mice

Cysteine-rich intestinal protein (CRIP) has a double zinc-finger motif called the LIM domain. The most elementary member of the Group 2 LIM-only protein family, CRIP was initially identified as a developmentally regulated intestinal gene. Subsequently, it was found to be highly expressed in immune cells. The structural portion of the rat CRIP gene is comprised of five exons extending over i.8 kb, with the two zinc-finger motifs of the LIM domain being divided among the first three exons. In addition to transcriptional regulatory elements previously identified in the promoter, consensus sequences for AP-1, AP2, Sp-1, and a glucocorticoid response element are located within the first intron. We have developed a line of transgenic mice that overexpress the rat CRIP gene with an expression profile that mirrors that of the endogenous gene. Driven by the homologous rat CRIP promoter, expression increased threefold to sevenfold in intestine, thymus, spleen, and lung over endogenous levels. The transgenic mice had only about 50% of the white blood cell count found in nontransgenic animals. Differential leukocyte counts showed transgenic animals had proportionately fewer lymphocytes and more monocytes, eosinophils, neutrophils. Flow cytometry data suggested that mice overexpressing CRIP have more CD4+/CD8+ thymic lymphocytes. These data suggest that CRIP plays a significant role in differentiation or maturation of cells with rapid turnover such as those found in the intestine and immune system.

Human cysteine-rich intestinal protein: cDNA cloning and expression of recombinant protein and identification in human peripheral blood mononuclear cells

Cysteine-rich intestinal protein (CRIP) is a small, 8.5-kDa protein with one double zinc-finger motif called a LIM domain. It is very abundant in intestine and some immune cells in rodents, and expression is influenced by development and the immune response. We have cloned a human CRIP cDNA from human small intestine poly(A)+ RNA by RT-PCR. Through sequencing, we found that the human intestinal CRIP protein (hCRIP) differed from the previously cloned rat CRIP by two amino acids (residues 8 and 58). hCRIP was expressed with the pET vector/bacterial system and isolated by gel filtration and ion-exchange chromatography. The protein was purified to homogeneity as confirmed by PAGE, Western blotting, and immunodetection. Recombinant hCRIP has a molecular mass of 8390 Da based on mass spectrum analysis. Southern analysis suggests that there are three copies of the CRIP gene in the human genome. hCRIP mRNA was detected by RT-PCR in human monocytes purified from peripheral blood and THP-1 cells, a human monocytic cell line. Incubation of THP-1 cells with 65Zn and chromatography of the cytosol show that a significant amount of the radioactivity is associated with CRIP as was shown previously for rat intestine. The results are consistent with a functional role for CRIP in proliferation/differentiation of specific cell types, particularly those associated with host defense.