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Transcriptional autoregulation controls pancreatic Ptf1a expression during development and adulthood

MOLECULAR AND CELLULAR BIOLOGY 2008年第17期28卷 5458-5468页

作者： Masui, Toshihiko Swift, Galvin H. Hale, Michael A. Meredith, David M. Johnson, Jane E. MacDonald, Raymond J. Univ Texas SW Med Ctr Dallas Dept Mol Biol Dallas TX 75390 USA Univ Texas SW Med Ctr Dallas Ctr Neurosci Dallas TX 75390 USA

The basic helix-loop-helix ( bHLH) transcription factor PTF1a is critical to the development of the embryonic pancreas. It is required early for the formation of the undifferentiated tubular epithelium of the nascent pancreatic rudiment and then becomes restricted to the differentiating acinar cells, where it directs the transcriptional activation of the secretory digestive enzyme genes. Here we report that the complex temporal and spatial expression of Ptf1a is controlled by at least three separable gene-flanking regions. A 14.8-kb control domain immediately downstream of the last Ptf1a exon is highly conserved among mammals and directs expression in the dorsal part of the spinal cord but has very little activity in the embryonic or neonatal pancreas. A 13.4-kb proximal promoter domain initiates limited expression in cells that begin the acinar differentiation program. The activity of the proximal promoter domain is complemented by an adjacent 2.3-kb autoregulatory enhancer that is able to activate a heterologous minimal promoter with high-level penetrance in the pancreases of transgenic mice. During embryonic development, the enhancer initiates expression in the early precursor epithelium and then superinduces expression in acinar cells at the onset of their development. The enhancer contains two evolutionarily conserved binding sites for the active form of PTF1a, a trimeric complex composed of PTF1a, one of the common bHLH E proteins, and either RBPJ or RBPJL. The two sites are essential for acinar cell-specific transcription in transfected cell lines and mice. In mature acinar cells, the enhancer and PTF1a establish an autoregulatory loop that reinforces and maintains Ptf1a expression. Indeed, the trimeric PTF1 complex forms dual autoregulatory loops with the Ptf1a and Rbpjl genes that may maintain the stable phenotype of pancreatic acinar cells.

关键词： .epithelium pancreatic bHLH Enhancer acinar Nascent autoregulation basic helix-loop-helix autoregulatory Ptf digestive enzyme

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Requirement of multiple lysine residues for the transcriptional activity and the instability of Hes7

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BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 2008年第1期372卷 142-146页

作者： Ishii, Akiko Kobayashi, Taeko Kageyama, Ryoichiro Kyoto Univ Inst Virus Res Sakyo Ku Kyoto 6068507 Japan Japan Sci & Technol Agcy CREST Kyoto 6068507 Japan

The basic helix-loop-helix (bHLH) gene Hes7 is expressed in an oscillatory manner and regulates the periodic somite formation. Oscillatory expression of Hes7 depends on negative feedback and rapid degradation of the gene products, but the precise mechanisms of how the transcriptional activity and the degradation of Hes7 protein are regulated remain to be analyzed. Here, we found that lysine residues (K22, K52, and K55) in the bHLH domain are essential not only for the instability of Hes7 protein but also for the transcriptional repressor activity. Introduction of lysine-to-arginine mutations into the bHLH domain led to stabilization of Hes7 protein and to abnormalities in either the N box-binding activity or partner preference in heterodimer formation. These results indicate that common amino acid residues are involved in both the transcriptional repressor activity and the instability of Hes7 protein, suggesting of a critical link between the transcription and degradation control. (C) 2008 Elsevier Inc. All rights reserved.

关键词： basic helix-loop-helix Hes7 protein stability transcriptional repressor

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Dimerization of yeast transcription factors Ino2 and Ino4 is regulated by precursors of phospholipid biosynthesis mediated by Opi1 repressor

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CURRENT GENETICS 2008年第1期54卷 35-45页

作者： Kumme, Jacqueline Dietz, Martin Wagner, Christian Schueller, Hans-Joachim Inst Genet & Funkt Genomforsch D-17487 Greifswald Germany

Structural genes of phospholipid biosynthesis in the yeast S. cerevisiae are activated by the heterodimeric transcription factor Ino2 + Ino4, binding to ICRE (inositol/choline-responsive element) promoter motifs. In the presence of phospholipid precursors inositol and choline, Ino2-dependent activation is inhibited by the Opi1 repressor which interacts with Ino2. In this work, we systematically investigated the importance of regulatory mechanisms possibly affecting ICRE-dependent gene expression. Autoregulatory expression of INO2, INO4 and OPI1 was abolished by promoter exchange experiments, showing that autoregulation of regulators contributes to the degree of differential gene expression but is not responsible for it. Using GFP fusion proteins, Ino2 and Ino4 were found to localize to the nucleus under conditions of repression and derepression. Interestingly, nuclear localization of Ino2 required a functional INO4 gene. Targeting of a lexA-Ino2 fusion to a heterologous promoter containing lexA operator motifs revealed a constitutive gene activation which was not influenced by phospholipid precursors. We could show that Ino2-dependent activation of a lexA-Ino4 fusion is affected by inositol and choline. Since gene activation required interaction of Ino2 and Ino4 mediated by their helix-loop-helix domains, formation/dissociation of the heterodimer must be considered as an important step of target gene regulation.

关键词： phospholipid biosynthesis inositol Ino2 Saccharomyces cerevisiae transcriptional regulation basic helix-loop-helix

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A novel molecular recognition motif necessary for targeting photoactivated phytochrome signaling to specific basic helix-loop-helix transcription factors

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PLANT CELL 2004年第11期16卷 3033-3044页

作者： Khanna, R Huq, E Kikis, EA Al-Sady, B Lanzatella, C Quail, PH Univ Calif Berkeley Dept Plant & Microbial Biol Berkeley CA 94720 USA USDA ARS Ctr Plant Gene Express Albany CA 94710 USA

The phytochrome (phy) family of sensory photoreceptors (phyA to phyE) in Arabidopsis thaliana control plant developmental transitions in response to informational light signals throughout the life cycle. The photoactivated conformer of the photoreceptor Pfr has been shown to translocate into the nucleus where it induces changes in gene expression by an unknown mechanism. Here, we have identified two basic helix-loop-helix (bHLH) transcription factors, designated PHYTOCHROME-INTERACTING FACTOR5 (PIF5) and PIF6, which interact specifically with the Pfr form of phyB. These two factors cluster tightly with PIF3 and two other phy-interacting bHLH proteins in a phylogenetic subfamily within the large Arabidopsis bHLH (AtbHLH) family. We have identified a novel sequence motif (designated the active phytochrome binding [APB] motif) that is conserved in these phy-interacting AtbHLHs but not in other noninteractors. Using the isolated domain and site-directed mutagenesis, we have shown that this motif is both necessary and sufficient for binding to phyB. Transgenic expression of the native APB-containing AtbHLH protein, PIF4, in a pif4 null mutant, rescued the photoresponse defect in this mutant, whereas mutated PIF4 constructs with site-directed substitutions in conserved APB residues did not. These data indicate that the APB motif is necessary for PIF4 function in light-regulated seedling development and suggest that conformer-specific binding of phyB to PIF4 via the APB motif is necessary for this function in vivo. Binding assays with the isolated APB domain detected interaction with phyB, but none of the other four Arabidopsis phys. Collectively, the data suggest that the APB domain provides a phyB-specific recognition module within the AtbHLH family, thereby conferring photoreceptor target specificity on a subset of these transcription factors and, thus, the potential for selective signal channeling to segments of the transcriptional network.

关键词： .designated subfamily cally photoreceptors basic helix-loop-helix PIF photoactivated phytochrome PhyE Pfr form phyB phyA phy family Al-Sady APB motif

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Developmental and evolutionary aspects of the basic helix-loop-helix transcription factors Atonal-like 1 and Achaete-scute homolog 2 in the jellyfish

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DEVELOPMENTAL BIOLOGY 2004年第2期269卷 331-345页

作者： Seipel, K Yanze, N Schmid, V Univ Basel Inst Zool Bioctr Pharmactr CH-4056 Basel Switzerland

The close functional link of nerve and muscle cells in neuromuscular units has led to the hypothesis of a common evolutionary origin of both cell types. Jellyfish are well suited to evaluate this theory since they represent the most basal extant organisms featuring both striated muscle and a nervous system. Here we describe the structure and expression of two novel genes for basic helix-loop-helix (bHLH) transcription factors, the Achaete-scute B family member Ash2 and the Atonal-like gene Atl1, in the hydrozoan jellyfish Podocoryne carnea. Ash2 is expressed exclusively in larval and adult endoderm cells and may be involved in differentiation of secretory cells. Atl1 expression is more widespread and includes the developing striated muscle as well as mechanosensory and nerve cell precursors in the medusa tentacles. Moreover, Atl1 expression is upregulated in proliferating nerve cell precursors arising from adult striated muscle cells by transdifferentiation in vitro. Likewise, the neuronal marker gene NP coding for the RFamide neuropeptide is expressed not only in mature nerve cells but also transiently in the developing muscle. The molecular evidence is concurrent to the hypothesis that muscle and nerve cells are closely linked in evolution and derive from a common myoepithelial precursor. (C) 2004 Elsevier Inc. All rights reserved.

关键词： Achaete-scute atonal basic helix-loop-helix Cnidaria evolution muscle nerve neuropeptide Podocoryne carnea transdifferentiation

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The Notch signaling cascade in neuroblastoma: role of the basic helix-loop-helix proteins HASH-1 and HES-1

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CANCER LETTERS 2004年第2期204卷 171-178页

作者： Axelson, H Lund Univ Hosp MAS Div Mol Med Dept Lab Med S-20502 Malmo Sweden

Neuroblastoma is a childhood tumor originating from cells of the developing sympathetic nervous system. The disease exhibits a remarkable phenotypic diversity reflected in the outcome, ranging from spontaneous regression to fatal disease. Mammalian achaete-scute homologue 1 (MASH-1 or HASH-1 in humans), a basic helix-loop-helix transcription (bHLH) factor, is transiently expressed in migrating sympatho-adrenal precursor cells. This gene, which is essential for proper development of the sympathetic nervous system, is expressed in a majority of primary neuroblastomas and neuroblastoma cell lines indicating an embryonal origin of the tumor. One important negative regulator of MASH-1 expression is the bHLH factor hairy and Enhancer of split homolog-1 (HES-1), which in turn is under positive control of the Notch signaling cascade. When neuroblastoma cells are induced to differentiate, as indicated by neuronal morphology and upregulation of neuronal marker genes. the HASH-1 expression is rapidly downregulated with a concomitant, transient upregulation of HES-1. Furthermore, a constitutively active form of Notch-1 inhibits induced differentiation of neuroblastoma cells. In this review, the role of the Notch-signaling cascade in neuroblastoma, with focus on the bHLH factors HASH-1 and HES-1, will be discussed. (C) 2003 Elsevier Ireland Ltd. All rights reserved.

关键词： neuroblastoma basic helix-loop-helix MASH-1 HASH-1 HES-1 Notch-1 differentiation

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The mammalian basic helix-loop-helix/PAS family of transcriptional regulators

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INTERNATIONAL JOURNAL OF BIOCHEMISTRY & CELL BIOLOGY 2004年第2期36卷 189-204页

作者： Kewley, RJ Whitelaw, ML Chapman-Smith, A Univ Adelaide Sch Mol & Biomed Sci Biochem Adelaide SA 5005 Australia Univ Adelaide Ctr Mol Genet Dev Adelaide SA 5005 Australia

basic helix-loop-helix (bHLH)/PAS proteins are critical regulators of gene expression networks underlying many essential physiological and developmental processes. These include transcriptional responses to environmental pollutants and low oxygen tension, mediated by the aryl hydrocarbon (Dioxin) receptor and hypoxia inducible factors (HIF), respectively, and controlling aspects of neural development, mediated by the single minded (SIM) proteins. bHLH proteins must dimerise to form functional DNA binding complexes and bHLH/PAS proteins are distinguished from other members of the broader bHLH superfamily by the dimerisation specificity conferred by their PAS homology domains. bHLH/PAS proteins tend to be ubiquitous, latent signal-regulated transcription factors that often recognise variant forms of the classic E-box enhancer sequence bound by other bHLH proteins. Two closely related forms of each of the hypoxia inducible factors alpha and single minded proteins and the general partner protein, aryl hydrocarbon receptor nuclear translocator (ARNT), are present in many cell types. Despite high sequence conservation within their DNA binding and dimerisation domains, and having very similar DNA recognition specificities, the homologues are functionally non-redundant and biologically essential. While the mechanisms controlling partner choice and target gene activation that determine this functional specificity are poorly understood, interactions mediated by the PAS domains are essential. Information on structures and protein/protein interactions for members of the steroid hormone/nuclear receptor superfamily has ' contributed to our understanding of the way these receptors function and assisted the development of highly specific agonists and antagonists. Similarly, it is anticipated that developing a detailed mechanistic and structural understanding of bHLH/PAS proteins will ultimately facilitate drug design. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： basic helix-loop-helix PAS domain transcription ARNT

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Characterization of a set of phytochrome-interacting factor-like bHLH proteins in Oryza sativa

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BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 2007年第5期71卷 1183-1191页

作者： Nakamura, Yuko Kato, Takahiko Yamashino, Takafumi Murakami, Masaya Mizuno, Takeshi Nagoya Univ Sch Agr Mol Microbiol Lab Chikusa Ku Nagoya Aichi 4648601 Japan

The model dicotyledon Arabidopsis thaliana has a characteristic small sub-family of phytochrome-interacting bHLH (basic helix-loop-helix) factors, which are collectively designated the PIL (or PIF) (PHYTOCHROME INTERACTING FACTOR-LIKE) family proteins. In this study, we identified and characterized a set of highly homologous members (designated OsPIL11 to OsPIL16) in the model monocotyledon rice (Oryza sativa). Some of them (OsPIL11, OsPIL12, and OsPIL13) showed the ability to interact with the putative OsPRR1 (PSEUDO-RESPONSE REGULATOR 1) clock component, as far as the results of yeast two-hybrid assays were concerned. It was found that the expression of OsPIL13 is under the control of circadian rhythms (clock), while the expression of OsPIL15 is negatively regulated by light upon the onset to light exposure of etiolated seedlings. When the rice genes (OsPIL11 to OsPIL15) were over-expressed in A. thaliana, the resulting transgenic seedlings displayed anomalous morphologies with very long hypocotyls during early photomorphogenesis. These results suggest the view that the identified OsPILs are functional counterparts (or orthologs) of AtPILs, which are known to play important roles in red light-mediated (phyA and/or phyB-dependent) signal transduction pathways at immediate positions downstream of the photoreceptor in A. thaliana.

关键词： Arabidopsis thaliana Oryza sativa basic helix-loop-helix light signal transduction circadian clock

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The rice bHLH protein OslRO2 is an essential regulator of the genes involved in Fe uptake under Fe-deficient conditions

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PLANT JOURNAL 2007年第3期51卷 366-377页

作者： Ogo, Yuko Itail, Reiko Nakanishi Nakanishi, Hiromi Kobayashi, Takanori Takahashi, Michiko Mori, Satoshi Nishizawal, Naoko K. Univ Tokyo Grad Sch Agr & Life Sci Bunkyo Ku Tokyo 1138657 Japan JST CREST Kawaguchi Shi Saitama 3320012 Japan

Iron (Fe) deficiency is a major abiotic stress in crop production. Although responses to Fe deficiency in graminaceous plants, such as increased production and secretion of mugineic acid family phytosiderophores (MAs), have been described, the gene regulation mechanisms related to these responses are largely unknown. To elucidate the regulation mechanisms of the genes related to Fe acquisition in graminaceous plants, we characterized the Fe-deficiency-inducible basic helix-loop-helix transcription factor OsIRO2 in rice. In yeast cells, OsIRO2 functioned as a transcriptional activator. In rice, overexpression of OsIRO2 resulted in increased MAs secretion, whereas repression of OsIRO2 resulted in lower MAs secretion and hypersensitivity to Fe deficiency. Northern blots revealed that the expression of the genes involved in the Fe(III)-MAs;transport system was dependent on OsIRO2. The expression of the genes for nicotianamine synthase, a key enzyme in MAs synthesis, was notably affected by the level of OsIRO2 expression. Microarray analysis demonstrated that OsIRO2 regulates 59 Fe-deficiency-induced genes in roots. Some of these genes, including two transcription factors upregulated by Fe deficiency, possessed the OsIRO2 binding sequence in their upstream regions. OsIRO2 possesses a homologous sequence of the Fe-deficiency-responsive cis-acting elements (IDEs) in its upstream region. We propose a novel gene regulation network for Fe-deficiency responses, including OsIRO2, IDEs and the two transcription factors.

关键词： basic helix-loop-helix iron-deficiency-responsive elements iron microarray mugineic acid family phytosiderophores rice

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Transcriptional regulation of yeast phospholipid biosynthetic genes

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BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS 2007年第3期1771卷 310-321页

作者： Chen, Meng Hancock, Leandria C. Lopes, John M. Wayne State Univ Dept Biol Sci Detroit MI 48202 USA

The last several years have been witness to significant developments in understanding transcriptional regulation of the yeast phospholipid structural genes. The response of most phospholipid structural genes to inositol is now understood on a mechanistic level. The roles of specific activators and repressors are also well established. The knowledge of specific regulatory factors that bind the promoters of phospholipid structural genes serves as a foundation for understanding the role of chromatin modification complexes. Collectively, these findings present a complex picture for transcriptional regulation of the phospholipid biosynthetic genes. The INO1 gene is an ideal example of the complexity of transcriptional control and continues to serve as a model for studying transcription in general. Furthermore, transcription of the regulatory genes is also subject to complex and essential regulation. In addition, databases resulting from a plethora of genome-wide studies have identified regulatory signals that control one of the essential phospholipid biosynthetic genes, PIS1. These databases also provide significant clues for other regulatory signals that may affect phospholipid biosynthesis. Here, we have tried to present a complete summary of the transcription factors and mechanisms that regulate the phospholipid biosynthetic genes. (c) 2006 Elsevier B.V. All rights reserved.

关键词： transcription regulation chromatin modification chromatin remodelling regulators activators repressors INO1 basic helix-loop-helix autoregulation

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