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The prostanoid Prostacyclin plays diverse physiologic roles within the vasculature and other systems, and is widely implicated in several cardiovascular, pulmonary and renal diseases. Despite this, knowledge of the factors regulating expression of the I prostanoid receptor (the IP) remained largely unknown. This review details recent advances in understanding the key transcriptional regulators determining expression of the PTGIR gene in the human vasculature and the identification of novel interacting partners of the IP that impact on its function therein. Included in this are the trans -acting factors that regulate expression of the PTGIR under basal- and regulated-conditions, particularly those determining its up-regulation in response to cellular differentiation, estrogen and low serum-cholesterol. Moreover, the functional implications of the interactions between the IP with PDZK1, a multi PDZ-domain containing protein essential for reverse-cholesterol transport and endothelialization, and the IP with IKEPP, the intestinal and kidney enriched PDZ protein, for the role of the prostacyclin-IP axis within the vasculature are reviewed. [ABSTRACT FROM AUTHOR]

Primary kidney macrophage (PKM) cultures derived from goldfish hematopoietic tissues develop from early progenitors to mature macrophages in response to endogenous growth factor(s). When grown in vitro, PKM shift from a proliferative phase, where most of the proliferation and differentiation events take place, to a senescence phase, where there is cessation of proliferation and differentiation events and ultimately cell death through a process of apoptosis. The phenotypic changes of PKM from the proliferative to senescence phase are a reflection of specific changes in gene expression; therefore, comparison of gene expression patterns between the two phases should lead to the identification of macrophage genes directly involved in the positive and negative regulation of hematopoietic events, as well as genes that are modulated downstream from these regulatory points. Differential cross-screening of the proliferative phase PKM cDNA library using proliferative and senescence phase 32P-labeled cDNA probes identified several differentially expressed genes. Specifically, initial screen of 9200 clones yielded 734 differential primary clones that were isolated and analyzed using a PCR-based secondary screen. The majority of these clone isolates encoded a single transcript as determined by PCR amplification of the primary clones. The secondary screen confirmed the differential expression of 306 clones (3.32% of the total number of screened clones). Two hundred and forty four clones were sequenced; 158 and 86 were preferentially expressed during proliferative and senescence phases, respectively. Several potential candidates of fish macrophage hematopoiesis were identified. These include, for example, zinc finger protein 147, nucleophosmin, 14-3-3 protein, adenine nucleotide translocator 2 (ANT2), granulin, survivin-1, and apoptosis inhibitor-5. In addition, several potential markers of macrophage differentiation and/or function were identified and their expression patterns characterized across three distinct stages of macrophage development in vitro. These include legumain, CD63, interferon-inducible protein, macrosialin (CD68), transcription factor MafB, and the molecular chaperone BiP/GRP78. These analyses will facilitate future characterization of macrophage developmental events by providing a more global perspective of various facets of macrophage hematopoiesis. [Copyright &y& Elsevier]

Dexamethasone and transforming growth factor-β (TGF-β) show contrary effects on differentiation of adipocytes. Dexamethasone stimulates adipocyte differentiation whereas TGF-β inhibits it. In the present study, we investigated whether dexamethasone could reverse the TGF-β-mediated inhibition of preadipocyte differentiation. Primary rat preadipocytes, obtained from Sprague–Dawley rats, were pretreated with dexamethasone in the presence or absence of TGF-β, prior to the induction of differentiation. Co-treatment of dexamethasone and TGF-β before inducing differentiation reversed the TGF-β-mediated inhibition of preadipocyte differentiation. In order to elucidate the mechanism by which dexamethasone reversed the effect of TGF-β on the inhibition of preadipocyte differentiation, the expression of CCAAT/enhancer binding protein-α (C/EBPα) and peroxisome proliferator-activated receptor γ (PPARγ) was examined. Dexamethasone increased C/EBPα and PPARγ expression in the absence of TGF-β and also recovered the TGF-β-mediated suppression of C/EBPα expression in preadipocytes. Its effect was sustained in differentiated adipocytes as well. However, those effects were not observed in 3T3-L1 preadipocytes or differentiated adipocytes. These results indicate that dexamethasone reverses the TGF-β-mediated suppression of adipocyte differentiation by regulating the expression of C/EBPα and PPARγ, which is dependent on the cellular context. [Copyright &y& Elsevier]

Interleukin-6 (IL-6) production is up-regulated by several stimuli through the activation of transcription factors. We have previously demonstrated that CCAAT/enhancer binding protein homologous protein (CHOP) positively regulates IL-6 production at the transcriptional level in the human melanoma cell line A375. In this study, we provide evidence that CHOP up-regulates the IL-6 transcription without binding to the IL-6 promoter. CHOP dimerized more preferentially with an inhibitory isoform of nuclear factor for IL-6 expression (LIP (liver-enriched inhibitory protein)) than with a positively acting isoform (LAP, liver-enriched activator protein). These results indicate that CHOP plays an important role in IL-6 production without binding to its promoter, probably by trapping protein(s) such as LIP, which would otherwise inhibit IL-6 transcription. [Copyright &y& Elsevier]

Very-long-chain acyl-CoA dehydrogenase (VLCAD) is a major enzyme catalysing the first step in mitochondrial β-oxidation of long-chain fatty acids. During analysis of the VLCAD promoter, we discovered that another gene, discs-large-related 4 (DLG4), overlaps VLCAD and is transcribed in the opposite direction. DLG4 encodes postsynaptic density-95 (PSD95) protein, which plays critical roles in the formation and maintenance of synaptic junctions. The transcription start site of the VLCAD gene was determined by primer extension analysis and the overlapping structure of VLCAD and DLG4 was clarified. VLCAD and DLG4 are arranged in a head-to-head orientation on chromosome 17p13, and share a 245 bp overlapping region that contains part of DLG4 exon 1 and the entire exon 1 of VLCAD including 62 bp of protein coding sequence. Despite the overlap of their 5′ ends, DLG4 and VLCAD exhibit peak mRNA expression in different tissues, suggesting that they are independently regulated at the transcriptional level. Interestingly, VLCAD and DLG4 genes do not overlap in the mouse or Drosophila genomes. [Copyright &y& Elsevier]

Transdifferentiation is the name used to describe the direct conversion of one differentiated cell type into another. Cells which have the potential to interconvert by transdifferentiation generally arise from adjacent regions in the developing embryo. For example, the liver and pancreas arise from the same region of the endoderm. The transdifferentiation of pancreas to liver (and vice versa) has been observed in animal experiments and in certain human pathologies. Understanding transdifferentiation is important to developmental biologists because it will help elucidate the cellular and molecular differences that distinguish neighbouring regions of the embryo. While the in vivo models for the transdifferentiation of liver to pancreas have been valuable, it is more difficult to extrapolate from these studies to individual changes at the cellular or molecular levels. The recent development of two in vitro systems (AR42J cells and embryonic pancreatic cultures) for the transdifferentiation of pancreas to liver has shown that an environmental change in the form of an exogenous glucocorticoid can cause the conversion of pancreatic exocrine cells into hepatocytes. The AR42J cell system has been used to elucidate the cell lineage and the molecular basis of transdifferentiation of pancreas to liver. [Copyright &y& Elsevier]

Selection of the translational initiation site in most eukaryotic mRNAs appears to occur via a scanning mechanism which predicts that proximity to the 5′ end plays a dominant role in identifying the start codon. This ‘position effect’ is seen in cases where a mutation creates an AUG codon upstream from the normal start site and translation shifts to the upstream site. The position effect is evident also in cases where a silent internal AUG codon is activated upon being relocated closer to the 5′ end. Two mechanisms for escaping the first-AUG rule – reinitiation and context-dependent leaky scanning – enable downstream AUG codons to be accessed in some mRNAs. Although these mechanisms are not new, many new examples of their use have emerged. Via these escape pathways, the scanning mechanism operates even in extreme cases, such as a plant virus mRNA in which translation initiates from three start sites over a distance of 900 nt. This depends on careful structural arrangements, however, which are rarely present in cellular mRNAs. Understanding the rules for initiation of translation enables understanding of human diseases in which the expression of a critical gene is reduced by mutations that add upstream AUG codons or change the context around the AUGSTART codon. The opposite problem occurs in the case of hereditary thrombocythemia: translational efficiency is increased by mutations that remove or restructure a small upstream open reading frame in thrombopoietin mRNA, and the resulting overproduction of the cytokine causes the disease. This and other examples support the idea that 5′ leader sequences are sometimes structured deliberately in a way that constrains scanning in order to prevent harmful overproduction of potent regulatory proteins. The accumulated evidence reveals how the scanning mechanism dictates the pattern of transcription – forcing production of monocistronic mRNAs – and the pattern of translation of eukaryotic cellular and viral genes. [Copyright &y& Elsevier]

In the mammalian hippocampus, there is a trisynaptic loop that has been often referred to in studies on learning and memory mechanisms and their physiological correlate, the long-term potentiation (LTP). The three sets of synapses are formed by the fibers of perforant pathway terminating on granule cells and by the mossy fibers and Schaeffer collaterals making connections with the pyramidal cells. Each of the three types of synapses can develop LTP. LTP is accompanied by changes in gene expression and it is the nuclear transcription, involving specific transcription factors, that is the starting point for the series of biological amplifications and consolidations both necessary for such sustained changes. The transcription factors are proteins that control gene expression, development and functional formation in every eukaryotic cell. Two categories of transcription factors have been defined to date: general factors that comprise at least 20 proteins to form multiple preinitiation complex at the TATA box (TATA rich sequence) or regulatory factors that bind to promoter or enhancer regions at specific sites on the DNA close to, or distant from, the TATA box. Transcription factors have been divided into five different major classes according to unique protein motifs. These include basic domain, zinc-finger, helix–turn–helix, β-Scaffold factors with minor groove contacts and other transcription factors not specifically classified. Much evidence has been accumulating in favor of the participation of several transcription factors in the consolidation of memory in the mammalian hippocampus following a spatial memory task. It is, therefore, of great importance that the involvement of transcription factors in de novo protein synthesis relevant to the synaptic mechanisms that mediate the formation of long-term memory should be summarized and discussed. No specific correlation between transduction of extracellular signals and expression of nuclear transcription factors, however, has been demonstrated to date. [Copyright &y& Elsevier]

Insulin-like growth factor II (IGF-II) is thought to play an important role in development and growth of vertebrates. In contrast to mammals, the IGF-II gene is expressed at a high level from the early stages of embryonic development until the adult stage and IGF-II peptide is produced in virtually all organs of bony fish, indicating a physiological importance of IGF-II ‘under water’. Therefore, we describe here the complete nucleotide sequence (accession no. X97225) and organization of the chum salmon IGF-II gene. In addition, the phylogenetic relationship of the IGF-II hormones is analysed. Although the chum salmon contains two non-allelic insulin and IGF-I genes, only one IGF-II gene could be identified. The chum salmon IGF-II gene consists of four exons and is comprised of 7992 bp from the putative transcription initiation site to the poly(A) site. Activation of the only promoter of the salmon IGF-II gene gives rise to a single 4 kb transcript. The fish IGF-II gene is much smaller and simpler organized than its known mammalian counterparts that are governed by several tissue-specific and developmental stage-dependent promoters. All known mammalian IGF-II genes to date have been found to form a conserved linkage group with the insulin and tyrosine hydroxylase (TH) genes and are organized as TH-insulin-IGF-II genomic locus. However, in our study we could find no linkage between the insulin and IGF-II genes, or between the insulin, TH and IGF-II genes, at least within approximately 20 kb of the chum salmon IGF-II genomic sequence. In spite of minor differences, the overall organization of the IGF-II genes turned out to be very similar in bony fish. A limited analysis of the phylogenetic relationship between IGF-II prohormones indeed showed a very conservative phylogenesis of IGF-II in bony fish that may indicate the particular significance of IGF-II in these animals. [Copyright &y& Elsevier]

Interleukin (IL)-1 modulates the expression of various genes in normal and tumor cells. We investigated the molecular mechanisms underlying IL-1β-induced expression of IL-8 mRNA and protein in human vascular smooth muscle cells (hVSMCs). P38 mitogen-activated protein kinase (MAPK) was activated after 5 min of IL-1β treatment, whereas the extracellular signal-regulated kinases, the c-jun amino-terminal kinases, and protein kinase B/Akt were not activated by IL-1β. IL-1β induced activation of a full-length IL-8 promoter–reporter construct. Deletional mutagenesis localized the IL-1β-responsive domains to two regions (−133 to −98 and −85 to −50) that contain consensus binding sites for activator protein-1 (AP-1) and nuclear factor-κB (NF-κB), respectively. Site-directed mutagenesis of the 133-bp minimal promoter confirmed that these sites were required for promoter activity. Electrophoretic mobility shift assays confirmed that IL-1β increased AP-1 and NF-κB DNA-binding activities in a time-dependent manner. SB203580, a specific P38 MAPK inhibitor, partially blocked IL-1β induction of IL-8 mRNA, IL-8 promoter activity, and AP-1 nuclear extract binding but not NF-κB DNA binding. Our data demonstrate that AP-1 and NF-κB are essential transcription factors for IL-1β-induced IL-8 gene expression in hVSMCs. P38 MAPK is involved in inducing IL-8 gene transcription via AP-1 activation in hVSMCs. [Copyright &y& Elsevier]

Myeloid blood cells comprise an important component of the immune system. Proper control of both lineage- and stage-specific gene expression is required for normal myeloid cell development and function. In recent years, a relatively small number of critical transcriptional regulators have been identified that serve important roles both in myeloid cell development and regulation of lineage-restricted gene expression in mature myeloid cells. This review summarizes our current understanding of the regulation of lineage- and stage-restricted transcription during myeloid cell differentiation, how critical transcriptional regulators control myeloid cell development, and how perturbations in transcription factor function results in the development of leukemia. [Copyright &y& Elsevier]