Multi-tissue transcriptomic study reveals the main role of liver in the chicken adaptive response to a switch in dietary energy source through the transcriptional regulation of lipogenesis.

BACKGROUND: Because the cost of cereals is unstable and represents a large part of production charges for meat-type chicken, there is an urge to formulate alternative diets from more cost-effective feedstuff. We have recently shown that meat-type chicken source is prone to adapt to dietary starch substitution with fat and fiber. The aim of this study was to better understand the molecular mechanisms of this adaptation to changes in dietary energy sources through the fine characterization of transcriptomic changes occurring in three major metabolic tissues - liver, adipose tissue and muscle - as well as in circulating blood cells. RESULTS: We revealed the fine-tuned regulation of many hepatic genes encoding key enzymes driving glycogenesis and de novo fatty acid synthesis pathways and of some genes participating in oxidation. Among the genes expressed upon consumption of a high-fat, high-fiber diet, we highlighted CPT1A, which encodes a key enzyme in the regulation of fatty acid oxidation. Conversely, the repression of lipogenic genes by the high-fat diet was clearly associated with the down-regulation of SREBF1 transcripts but was not associated with the transcript regulation of MLXIPL and NR1H3, which are both transcription factors. This result suggests a pivotal role for SREBF1 in lipogenesis regulation in response to a decrease in dietary starch and an increase in dietary PUFA. Other prospective regulators of de novo hepatic lipogenesis were suggested, such as PPARD, JUN, TADA2A and KAT2B, the last two genes belonging to the lysine acetyl transferase (KAT) complex family regulating histone and non-histone protein acetylation. Hepatic glycogenic genes were also down-regulated in chickens fed a high-fat, high-fiber diet compared to those in chickens fed a starch-based diet. No significant dietary-associated variations in gene expression profiles was observed in the other studied tissues, suggesting that the liver mainly contributed to the adaptation of birds to changes in energy source and nutrients in their diets, at least at the transcriptional level. Moreover, we showed that PUFA deposition observed in the different tissues may not rely on transcriptional changes. CONCLUSION: We showed the major role of the liver, at the gene expression level, in the adaptive response of chicken to dietary starch substitution with fat and fiber.

Inhibition of zygotic DNA repair: transcriptome analysis of the offspring in trout (Oncorhynchus mykiss).

Zygotic repair of the paternal genome is a key event after fertilization. Spermatozoa accumulate DNA strand breaks during spermatogenesis and can suffer additional damage by different factors, including cryopreservation. Fertilization with DNA-damaged spermatozoa (DDS) is considered to promote implantation failures and abortions, but also long-term effects on the progeny that could be related with a defective repair. Base excision repair (BER) pathway is considered the most active in zygotic DNA repair, but healthy oocytes contain enzymes for all repairing pathways. In this study, the effects of the inhibition of the BER pathway in the zygote were analyzed on the progeny obtained after fertilization with differentially DDS. Massive gene expression (GE; 61 657 unique probes) was analyzed after hatching using microarrays. Trout oocytes are easily fertilized with DDS and the high prolificacy allows live progeny to be obtained even with a high rate of abortions. Nevertheless, the zygotic inhibition of Poly (ADP-ribose) polymerase, upstream of BER pathway, resulted in 810 differentially expressed genes (DEGs) after hatching. DEGs are related with DNA repair, apoptosis, telomere maintenance, or growth and development, revealing a scenario of impaired DNA damage signalization and repair. Downregulation of the apoptotic cascade was noticed, suggesting a selection of embryos tolerant to residual DNA damage during embryo development. Our results reveal changes in the progeny from defective repairing zygotes including higher malformations rate, weight gain, longer telomeres, and lower caspase 3/7 activity, whose long-term consequences should be analyzed in depth.

The LIM-only protein FHL2 is a negative regulator of E4F1.

The E1A-targeted transcription factor E4F1 is a key player in the control of mammalian embryonic and somatic cell proliferation and survival. Mouse embryos lacking E4F die at an early developmental stage, whereas enforced expression of E4F1 in various cell lines inhibits cell cycle progression. E4F1-antiproliferative effects have been shown to depend on its capacity to repress transcription and to interact with pRb and p53. Here we show that full-length E4F1 protein (p120(E4F1)) but not its E1A-activated and truncated form (p50(E4F1)), interacts directly in vitro and in vivo with the LIM-only protein FHL2, the product of the p53-responsive gene FHL2/DRAL (downregulated in rhabdomyosarcoma Lim protein). This E4F1-FHL2 association occurs in the nuclear compartment and inhibits the capacity of E4F1 to block cell proliferation. Consistent with this effect, ectopic expression of FHL2 inhibits E4F1 repressive effects on transcription and correlates with a reduction of nuclear E4F1-p53 complexes. Overall, these results suggest that FHL2/DRAL is an inhibitor of E4F1 activity. Finally, we show that endogenous E4F1-FHL2 complexes form in U2OS cells upon UV-light-induced nuclear accumulation of FHL2.

Characterization of an enhancer element in the proximal promoter of the mouse glucagon receptor gene.

The 5'-flanking region of the mouse glucagon receptor has been previously cloned and two promoter regions were characterized. Functional analysis of the proximal promoter was now performed to characterize cis-acting element(s) regulating basal gene expression. Promoter analysis using deletion constructs in a rat cell line (CA-77) expressing the glucagon receptor, showed that the region from -64 to +127 relative to the proximal transcription start site was sufficient for maximal proximal promoter activity. A DNA sequence spanning the -28 to -16 region organized as an imperfect palindrome was demonstrated to be functional as a cis-acting enhancer. Constructs including several copies of this motif strongly increased activity of the heterologous thymidine kinase promoter. Gel mobility shift assays performed with different DNA fragments spanning this region confirmed that it specifically bound nuclear protein(s) from CA-77 cells, mouse MIN-6 cells or mouse liver. Mutations in the core sequence of this site impaired both reporter gene activity and nuclear protein binding. The palindrome is a novel DNA sequence with no homology to existing transcription factor binding site database. This is the first characterization of a functional cis-acting sequence into the proximal promoter of the mouse glucagon receptor that may support constitutive expression of the gene.

Potentiation of growth hormone-induced liver suppressors of cytokine signaling messenger ribonucleic acid by cytokines.

Endotoxin and proinflammatory cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNFalpha) induce a state of GH resistance. A new family of suppressors of cytokine signaling (SOCS), induced by cytokines activating the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway, has been recently identified as a negative feedback loop of intracellular signaling. Overexpression of some SOCS (SOCS-3, CIS, and SOCS-2) has been reported to inhibit the JAK-STAT pathway stimulated by GH. To assess the possible role of these three SOCS proteins in the GH resistance induced by endotoxin and cytokines, we investigated the regulation of their gene expression by endotoxin and GH in rat liver and by proinflammatory cytokines and GH in primary culture hepatocytes. Both GH and lipopolysaccharide induced the three SOCS messenger RNAs (mRNAs) in vivo. In vitro, GH also increased the liver mRNAs encoding SOCS-2, SOCS-3, and CIS. Although IL-1/beta and TNFalpha alone induced only weakly the expression of SOCS-3 and CIS, these cytokines strongly potentiated the induction of these two SOCS by GH. In contrast, IL-6 alone markedly induced SOCS-3 mRNA, but did not potentiate the GH action on SOCS-3 and CIS mRNAs. The GH induction of SOCS-2 was not potentiated by any of these cytokines. Considering the ability of these SOCS to inhibit the JAK-STAT pathway induced by GH, these results suggest that the overexpression of SOCS-3 and CIS mRNAs induced by IL-1beta and TNFalpha or by endotoxin in vivo may play a role in the GH resistance induced by sepsis.

Regulation of expression of the rat SOCS-3 gene in hepatocytes by growth hormone, interleukin-6 and glucocorticoids mRNA analysis and promoter characterization.

Suppressors of cytokine signalling (SOCS) represent a newly discovered family of molecules that seem to play an important role in the shutting off of cytokine and possibly peptide hormone action. Thus, understanding the mechanisms controlling their expression is of cardinal importance. In the present study, we have cloned the rat SOCS-3 gene and analyzed its expression and the functioning of its promoter in hepatocytes. Expression of SOCS-3 mRNA, which is very weak in freshly isolated cells, tended to increase when hepatocytes were incubated without hormones. Growth hormone (GH) and, to a much larger extent, interleukin-6 (IL-6) rapidly activated mRNA synthesis whereas glucocorticoids (GC) strongly inhibited both basal and hormone-dependent expressions. A short promoter fragment (-137/+35) responded maximally to GH and IL-6 (a threefold stimulation for each effector) and to GC (a 70-80% inhibition), whereas longer promoter sequences supported higher basal activity and lower positive hormonal responses. Deletion and mutation analyses indicated that all hormonal responses were dependent on two cis-acting sequences termed the G-rich and the A/T-rich elements. Only the A/T-rich element was active in a heterologous context, thus behaving as a typical enhancer. Unexpectedly, the two signal transducer and activator of transcription (STAT) binding sites found immediately upstream of the G-rich motif didn't seem to participate in either GH or IL-6 effect, despite the fact that one of them strongly responded to IL-6 when placed in front of a heterologous promoter. Finally, the negative regulation of SOCS-3 promoter by GC that may contribute to gene silencing in vivo, appeared to involve interactions of the GC receptor with other transcription factors and not direct binding to DNA, as no GC-response element was found in the sequence.

Structural and functional characterizations of the 5'-flanking region of the mouse glucagon receptor gene: comparison with the rat gene.

A putative proximal promoter was defined previously for the mouse glucagon receptor (GR) gene. In the present study, a distal promoter was characterized upstream from a novel non-coding exon revealed by the 5'-rapid amplification of cDNA ends from mouse liver tissue. The 5'-flanking region of the mouse GR gene was cloned up to 6 kb and the structural organization was compared to the 5' untranslated region of the rat gene cloned up to 7 kb. The novel exon, separated by an intron of 3.8 kb from the first coding exon, displayed a high homology (80%) with the most distal of the two untranslated exons found in the 5' region of the rat GR gene. The mouse distal promoter region, extending up to -1 kb from the novel exon, displayed 85% identity with the rat promoter. Both contain a highly GC-rich sequence with five putative binding sites for Sp1, but no consensus TATA or CAAT elements. To evaluate basal promoter activities, 5'-flanking sequences of mouse or rat GR genes were fused to a luciferase reporter gene and transiently expressed in a mouse and in a rat cell line, respectively or in rat hepatocytes. Both mouse and rat distal promoter regions directed a high level of reporter gene activity. Deletion of the Sp1 binding sites region or mutation of the second proximal Sp1 sequence markedly reduced the distal promoter activity of the reporter gene. The mouse proximal promoter activity was 2- to 3-fold less than the distal promoter, for which no functional counterpart was observed in the similar region of the rat gene.

Positive and negative elements modulate the promoter of the human liver-specific alpha2-HS-glycoprotein gene.

The human alpha2-HS-glycoprotein (AHSG) and the 63-kDa rat phosphoprotein (pp63) are homologous plasma proteins that belong to the fetuin family. AHSG and pp63 are involved in important functions such as inhibition of insulin receptor tyrosine kinase activity, inhibition of protease activities, and regulation of calcium metabolism and osteogenesis. Studies of the AHSG proximal promoter performed in vitro in rat and human cells indicate that several NF-1 and C/EBP binding sites exert a positive effect on its transcriptional activity. However, until now, no distal elements have been examined in this gene, in either species. We report that the human AHSG gene promoter acts in a liver-specific manner and is further controlled by three distal, 5'-flanking elements. The negative elements III and I are, respectively, located 5' and 3' of the positive element II. All three elements require the natural context of the human AHSG gene to fully exert their negative or positive effect. Element I harbours a single binding site for NF-1. This nuclear factor thus appears to be able to up- or downregulate the AHSG gene depending on the site it binds to. Elements I, II and possibly III are absent in the rodent Ahsg gene encoding pp63.

Isolation, characterization, and chromosomal localization of the human ENSA gene that encodes alpha-endosulfine, a regulator of beta-cell K(ATP) channels.

Human alpha-endosulfine is an endogenous regulator of the beta-cell K(ATP) channels. The recombinant alpha-endosulfine inhibits sulfonylurea binding to beta-cell membranes, reduces cloned K(ATP) channel currents, and stimulates insulin secretion from beta-cells. These properties led us to study the human ENSA gene that encodes alpha-endosulfine. Here, we describe the isolation, the partial characterization, and the chromosomal localization of the ENSA gene. The ENSA gene appears to be a 1.8-kb-long sequence that contains the transcription initiation site located 528 bp upstream of the initiation codon. The ENSA gene is intronless, and a single copy gene seems to be present in the genome. Finally, the ENSA gene co-localizes on human chromosome 14 (14q24.3-q31) with a locus for susceptibility to type 1 diabetes called IDDM11; thus, the ENSA gene represents an IDDM11 candidate.

Increased expression of tissue inhibitor of metalloproteinase-1 and loss of correlation with matrix metalloproteinase-9 by macrophages in asthma.

Alveolar macrophages (AMs) can mediate tissue destruction and repair by synthesizing matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) as well as inflammatory cytokines, which regulate their production. Imbalances between these enzymes and inhibitors may contribute to the tissue damage and remodeling seen in inflammatory diseases. In this study, we examined the role of AMs in chronic asthma. We have previously demonstrated an increased production of MMP-9 by AMs in untreated asthmatic patients as compared with healthy subjects, and in asthmatics treated with inhaled corticosteroids and patients with chronic bronchitis. We now report on the expression of TIMP-1, the inhibitor of MMP-9, and compare the levels and the regulation by cytokines of both MMP-9 and TIMP-1. Enzyme and inhibitor were measured using an enzyme immunoassay and immunoprecipitation. TIMP-1 steady-state mRNA levels were measured using the RNase protection assay. AMs from untreated asthmatics were found to produce more TIMP-1 both at protein and mRNA levels than AMs from other groups. The release of TIMP-1 and MMP-9 from individual AMs was significantly correlated in control populations and the molecules mainly complexed to each other, whereas this was not true for untreated asthmatics, indicating an imbalance between MMP-9 and TIMP-1 production. In the latter population, TIMP-1 release was inhibited by an anti-IL-6 antibody and MMP-9 release by anti-TNF-alpha, anti-IL-6, and anti-IL-1/beta antibodies. The imbalance of MMP-9 and TIMP-1 production, via the involvement of different cytokines, suggests that AMs may be involved in the abnormal repair observed in chronic asthma.

Characterization of three transcriptional repressor sites within the 3' untranslated region of the rat serine protease inhibitor 2.3 gene.

The activity of the rat serine protease inhibitor 2.3 gene (spi 2.3) is controlled by several positive promoter elements [Simar-Blanchet, A.-E., Paul, C., Mercier, L. & Le Cam, A. (1996) Eur. J. Biochem. 236, 638-648] and a negative element located in the 3' untranslated gene region (3' UTR) [Le Cam, A. & Legraverend, C. (1996) Eur. J. Biochem. 231, 620-627]. In the present studies, we dissected the 348-bp spi 2.3 3' UTR silencer to precisely define repressor sites and look for specifically interacting proteins. Three short elements referred to as A (nucleotides 1751-1776 in the cDNA), B (nucleotides 1812-1827) and C (nucleotides 1958-1974) sites repressed transcription from the homologous spi 2.3 promoter as well as from a heterologous minimal promoter containing the spi GAGA box enhancer. All three sites harbor a (TTTC) motif whose mutation affected silencer activity that was also dependent on flanking sequences. Those sites share the (TTTC) motif and a CCAAT/enhancer-binding-protein(C/EBP)-binding site with a fatty-acid-binding-protein gene promoter element shown to interact specifically with a transcriptional repressor [He, G. P., Muise, A., Wu Li, A. & Ro, H.-S. (1995) Nature 378, 92-96]. This repressor is however unlikely to mediate spi 2.3 3' UTR silencer action since it was not detected in rat hepatocytes. In vitro footprinting of the spi 2.3 3' UTR silencer region revealed a strong interaction with liver nuclear proteins. Among the six identified footprints, three of them (F-II, FIII and F-IV) bound C/EBPs and mapped in regions harboring the repressor function. Binding of C/EBPs to all three spi 2.3 3' UTR repressor sites, although rather weak, was confirmed by electrophoretic mobility shift assays that otherwise failed to reveal specific interactions with other liver nuclear proteins in vitro. However, none of the most largely liver expressed C/EBP species (i.e. alpha, beta and delta) activated the spi 2.3 3' UTR silencer function in NIH 3T3 cells, suggesting that binding of those transcription factors did not mediate the transcriptional repression.

Human alpha-endosulfine, a possible regulator of sulfonylurea-sensitive KATP channel: molecular cloning, expression and biological properties.

Sulfonylureas are a class of drugs commonly used in the management of non-insulin-dependent diabetes mellitus. Their therapeutic action results primarily from their ability to inhibit ATP-sensitive potassium (KATP) channels in the plasma membrane of pancreatic beta cells and thereby stimulate insulin release. A key question is whether an endogenous ligand for the KATP channel exists that is able to mimic the inhibitory effects of sulfonylureas. We describe here the cloning of the cDNA encoding human alpha-endosulfine, a 13-kDa peptide that is a putative candidate for such a role. alpha-Endosulfine is expressed in a wide range of tissues including muscle, brain, and endocrine tissues. The recombinant protein displaces binding of the sulfonylurea [3H]glibenclamide to beta cell membranes, inhibits cloned KATP channel currents, and stimulates insulin secretion. We propose that endosulfine is an endogenous regulator of the KATP channel, which has a key role in the control of insulin release and, more generally, couples cell metabolism to electrical activity.

Transcription of the rat serine protease inhibitor 2.1 gene in vivo: correlation with GAGA box promoter occupancy and mechanism of cytokine-mediated down-regulation.

Two GH-response elements (GHREs) and a single glucocorticoid (GC)-response element were found to regulate activity of the rat serine protease inhibitor 2.1 gene (spi 2.1) promoter in vitro. To assess the physiological relevance of these observations, we have investigated the relationship existing between the level of spi 2.1 gene transcription, structural modifications of the chromatin, and in vivo nuclear protein-promoter interactions monitored by genomic footprinting, in control, hypophysectomized, and inflamed rats. We also addressed the mechanism of inflammation-mediated gene down-regulation. We found that a high level of spi 2.1 gene transcription correlates with hypersensitivity of the promoter to deoxyribonuclease I (DNase I) and maximal occupancy of the GAGA box (GHRE-I). The failure of GAGA-box binding proteins (GAGA-BPs) to interact with the GAGA box appears to result from an impairment in GH action due to its absence (i.e. hypophysectomized animals) or to the appearance of a cytokine-mediated GH-resistant state (i.e. inflamed rats) in liver. Unlike the GAGA box, signal transducer and activator of transcription (STAT) factor-binding sites included in the GHRE-II were never found to be protected against DNase I attack but displayed a differential DNase I reactivity depending on the level of gene transcription. Alterations in DNase I reactivity of the GC-response element region suggest that GC receptor-GC complexes may associate, in a transient manner, with the promoter in the actively transcribing control state. Taken together, our studies suggest a mechanism of spi 2.1 gene activation in vivo whereby the GH-dependent chromatin remodeling caused by or concomitant to the recruitment of GAGA-box binding proteins is the first compulsory and presumably predominant step.

Growth hormone-mediated transcriptional activation of the rat serine protease inhibitor 2.1 gene involves both interleukin-1 beta-sensitive and -insensitive pathways.

Growth hormone (GH)-dependent activation of the rat serine protease inhibitor 2.1 (spi 2.1) gene in vivo requires both a modification of the chromatin structure and the activation of transcription factors mediated by the tyrosine protein Janus kinase JAK2. To address the question of the relationship between those two GH effects, we used interleukin 1 beta (Il-1 beta) that was previously shown to inhibit spi 2.1 gene expression. In cultured hepatocytes from normal rats, Il-1 beta did not antagonize GH-dependent stimulation of promoter activity (i.e., in episomal constructs) mediated by transcription factors activated by JAK2. In hepatocytes from inflamed rats, GH triggered JAK2-dependent activation of transcription factors as in control cells but failed to stimulate genomic spi 2.1 gene expression. It thus appears that the Il-1 beta-insensitive activation of transcription factors by GH is independent of its action on the nucleosomal structure of the spi 2.1 gene which, in contrast, is sensitive to this cytokine.

Alpha endosulfine is a novel molecule, structurally related to a family of phosphoproteins.

We have observed that alpha endosulfine, the 13KDa form of the endogenous ligand for sulfonylurea receptor recently isolated from porcine brain, displays strong similarities with a phosphoprotein of similar size previously isolated from bovine brain and called ARPP-19. To determine whether the two proteins are different entities, we developed an RT-PCR strategy for analyzing the main portion of bovine alpha endosulfine. We show that alpha endosulfine and ARPP-19 are different entities from the same family of proteins, coded by distinct genes.

Regulation of expression of the rat serine protease inhibitor 2.3 gene by glucocorticoids and interleukin-6. A complex and unusual interplay between positive and negative cis-acting elements.

The rat serine protease inhibitor 2.3 gene (spi 2.3) is almost completely silent in normal animals and is transiently expressed during acute inflammation. It encodes a potential anti-elastase which is likely to play a major physiological role for the host defense. Two well-known inflammatory mediators, glucocorticoids and interleukin-6 (IL-6) activate the spi 2.3 promoter and increase steady-state levels of mRNA in cultured hepatocytes. GC activation is mediated by a single glucocorticoid-response element which seems to act autonomously. A unique array of four functional IL-6-response sites was identified in the spi 2.3 promoter. Three of them (C-II--IV) bear structural identity to the CCAAT/enhancer-binding-protein-binding site consensus sequence, whereas the fourth closely resembles the consensus kappa B nuclear factor recognition motif. The C-IV element, which is the most active, contains the motif 5'-CTGGGA and binds the IL-6-inducible acute-phase response factor present in liver nuclear extracts from inflamed rats. Both basal and IL-6-dependent activities of each individual cytokine-response element tested separately are strongly down regulated by a recently identified regulatory sequence, located in the 3' untranslated region of the spi 2.3 gene. However, this repressor element does not significantly affect overall IL-6-dependent spi 2.3 promoter activity. This suggests that, in the context of the active gene in vivo, all four IL-6-response sites, which are largely redundant, cooperate to overcome the strong repressive effect of the 3' untranslated region silencer and are needed to bring about a maximal IL-6 response. These data reveal a novel type of regulation of an acute-phase gene involving different classes of IL-6-response elements controlled by a repressor and acting in conjunction with a glucocorticoid-response element.

Transcriptional repression, a novel function for 3' untranslated regions.

The transcription rates of the rat serine protease inhibitor 2.3 and 2.1 genes (spi 2.3 and spi 2.1), which are normally very low and high, respectively, are inversely modulated during inflammation. Two growth-hormone-response elements (GHRE-I and GHRE-II) maintain the spi 2.1 gene under the stringent control of growth hormone [Le Cam, A., Pantescu, V., Paquereau, L., Legraverend, C., Fauconnier, G. & Asins, G. (1994) J. Biol. Chem. 269, 21532-21539], whereas spi 2.3 appears to escape control by this hormone, despite the presence in its promoter of a functional GHRE-I. A major difference between these two otherwise very similar genes is the presence in spi 2.3 of a specific 348-bp extension of the 3' untranslated region (3' UTR). Inserting this 3' UTR element downstream of the polyadenylation signal or upstream of the spi 2.3 promoter in constructs containing the chloramphenicol acetyltransferase gene strongly decreases basal transcription and inhibits growth-hormone-stimulated transcription, but poorly affects transcriptional stimulation by dexamethasone or interleukin-6. The spi 2.3 3' UTR extension also inhibits, basal and growth-hormone-induced transcription from the spi 2.1 promoter. Repressor activity appears to be distributed throughout the specific extension of the 3' UTR and seems to involve interactions with two types of 5' cis-acting promoter elements. The first is the GAGA box, a key control spi promoter element, whose mutation faithfully reproduces the effects of the 3' UTR silencer on spi 2.1 and spi 2.3 promoters. The second is represented by CCAAT enhancer-binding-protein-(C/EBP)-binding sites, whose functions are severely impaired by the spi 2.3-specific 3' UTR extension. The presence of this silencer in the spi 2.3 gene very likely accounts for the lack of basal of transcription in vivo and for induction of the gene during acute inflammation.

cis-Acting elements controlling transcription from rat serine protease inhibitor 2.1 gene promoter. Characterization of two growth hormone response sites and a dominant purine-rich element.

The cis-acting elements that are functionally important for the basal, the growth hormone (GH), and the glucocorticoid hormone (GC) regulation of expression of the rat serine protease inhibitor 2.1 gene (spi 2.1) were mapped. Normal rat hepatocytes were transiently transfected with constructs harboring deleted or mutated versions of the spi 2.1 proximal promoter region fused to the chloramphenicol acetyltransferase gene. A purine-rich sequence (GAGA box, nucleotides -57 to -45), whose mutation or deletion almost completely knocks out both basal and hormone-stimulated promoter activities, plays the role of a key control element. A positive GC response element, spanning nucleotides -88 to -74, confers GC responsiveness to a heterologous promoter. Two structurally unrelated GH-response elements (GHRE) were identified. GHRE-II (nucleotides -136 to -104) contains a CCAAT enhancer binding protein binding site whose mutation completely abolishes its GH-dependent enhancer function. GHRE-I, which spans nucleotides -61 to +8, is not an enhancer element. Its GH-dependent activity depends on the preservation of the distance separating the GAGA box and elements of the basic transcriptional machinery. Taken together, these results have revealed the existence of an apparently new type of promoter functioning that strictly depends on the integrity of a key regulatory (G + A) motif.

Insulin and interleukin-1 differentially regulate pp63, an acute phase phosphoprotein in hepatoma cell line.

We have reported previously that the phosphoprotein pp63, an acute phase protein, which has been recently identified as the rat fetuin, was capable of blocking the mitogenic effect of insulin on the rat Fao hepatoma cell line, without affecting metabolic effects of the hormone. Only the phosphorylated form of the protein has been shown to exhibit both anti-tyrosine kinase and growth inhibitory properties. In this study, we used the FTO-2B rat hepatoma cell line to analyze the mechanisms involved in the control of synthesis and/or phosphorylation of pp63. For this purpose, we investigated the action of effectors known to modulate hepatic functions, such as cytokines (interleukin (IL)-1 beta and IL-6), which regulate the production of acute phase proteins, and insulin, which elicits profound effects on hepatocyte metabolism. Here, we demonstrate that IL-1 beta diminished markedly the pp63 production by affecting its mRNA transcription and that the cytokine was able to modify the N-glycosylation process of the protein. In contrast, insulin did not affect the biosynthesis of pp63 but dramatically decreased its extent of phosphorylation.