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New members of the Drosophila Myc transcription factor subfamily revealed by a genome-wide examination for basic helix-loop-helix genes

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MECHANISMS OF DEVELOPMENT 2001年第1-2期104卷 99-104页

作者： Peyrefitte, S Kahn, D Haenlin, M Ctr Dev Biol CNRS UMR 5547 F-31062 Toulouse France INRA CNRS Lab Biol Mol Relat Plantes Microorganismes F-31326 Castanet Tolosan France

The basic helix-loop-helix (bHLH) proteins represent an evolutionary conserved class of transcription factors that are known to play important roles in cell determination and differentiation during animal embryonic development. Following an exhaustive search of the complete Drosophila genome sequence using a PSI-BLAST strategy, we identified 19 new genes, bringing the total number of bHLH-encoding genes in the Drosophila genome to 56. These new genes belong to various subfamilies of bHLH transcription factors, such as the Daughterless, Hairy-Enhancer of split, bHLH-PAS or bHLHZip subfamilies. The embryonic expression pattern of each of these new genes has been analyzed by in situ hybridization. By looking for closely structurally related motifs, we found two genes that represent likely orthologues of vertebrate Mnt and Mix. Together with previous reports, our data suggest that, similar to networks involved in neurogenesis and myogenesis, the network of Myc-related genes has been globally conserved throughout evolution. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.

关键词： Drosophila basic helix-loop-helix genome

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Differential regulation of basic helix-loop-helix mRNAs in the dentate gyrus following status epilepticus

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NEUROSCIENCE 2001年第1期106卷 79-88页

作者： Elliott, RC Khademi, S Pleasure, SJ Parent, JM Lowenstein, DH Beth Israel Deaconess Med Ctr Dept Neurol Boston MA 02215 USA Harvard Univ Sch Med Program Brain Plast & Epilepsy Boston MA 02115 USA

In various chemoconvulsant models of human temporal lobe epilepsy, the induction of epiteptogenesis by a prolonged period of continuous seizure activity is accompanied by significant changes in hippocampal structure. These changes include an increase in neurogenesis within the proliferative subgranular zone (SGZ) of the dentate gyrus and induction of mossy fiber sprouting in mature dentate granule cells. As dentate granule cell neurogenesis and axon outgrowth are also hallmarks of hippocampal development, we hypothesized that molecules involved in normal development may also play a role in similar changes associated with epileptogenesis. To begin to test this hypothesis, we have analyzed the expression patterns of multiple members of the basic helix-loop-helix (bHLH) family of transcription factors in both normal and epileptic adult rats. bHLH protein expression has been found recently in dentate, granule cells at specific developmental stages, and analysis of developmental models suggests specific neural differentiation functions for these molecules. We show that mRNA expression of all seven bHLH family members examined in this study, as well as the divergent homeobox protein Prox1, is present in the adult. Patterns of expression varied considerably between family members, ranging from the limited expression of Mash1 in the neurogenic SGZ of the dentate, gyrus to the scattered, widespread profile of Hes5 throughout the dentate gyrus and the hippocampus proper. Moreover, these varied profiles of expression were differentially regulated following status epilepticus, with some increasing (Mash1, Id2), some falling (Hes5, Prox1), and others remaining mostly unchanged (NeuroD/BETA2, NeuroD2/NDRF, Id3, Rath2/Nex1). While the function of these molecules in the adult brain remains to be characterized, our findings support the idea that molecules controlling cell-fate decisions in the developing dentate gyrus are also operative during seizure-induced neurogenesis and plasti

关键词： basic helix-loop-helix seizures epilepsy neurodevelopment neurogenesis sprouting

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Promotion of cell cycle progression by basic helix-loop-helix E2A

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MOLECULAR AND CELLULAR BIOLOGY 2001年第18期21卷 6346-6357页

作者： Zhao, F Vilardi, A Neely, RJ Choi, JK Univ Penn Dept Pathol & Lab Med Philadelphia PA 19104 USA Univ Penn Dept Genet Philadelphia PA 19104 USA

Normal B-cell development requires the E2A gene and its encoded transcription factors E12 and E47. Current models predict that E2A promotes cell differentiation and inhibits G(1) cell cycle progression. The latter raises the conundrum of how B cells proliferate while expressing high levels of E2A protein. To study the relationship between E2A and cell proliferation, we established a tissue culture-based model in which the activity of E2A can be modulated in an inducible manner using E47R, an E47-estrogen fusion construct, and E47ERT, a dominant negative E47-estrogen fusion construct. The two constructs were subcloned into retroviral vectors and expressed in the human pre-B-cell line 697, the human myeloid progenitor cell line K562, and the murine fibroblastic cell line NTH 3T3. In both B cells and non-B cells, suppression of E2A activity by E47ERT inhibited G(1) progression and was associated with decreased expression of multiple cyclins including the G(1)-phase cyclin D2 and cyclin D3. Consistent with these findings, E2A null mice expressed decreased levels of cyclin D2 and cyclin D3 transcripts. In complementary experiments, ectopic expression of E47R promoted G(1) progression and was associated with increased levels of multiple cyclins, including cyclin D2 and cyclin D3. The induction of some cyclin transcripts occurred even in the absence of protein synthesis. We conclude that, in some cells, E2A can promote cell cycle progression, contrary to the present view that E2A inhibits G(1) progression.

关键词： .promotes cell development basic helix-loop-helix

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DNA binding properties of basic helix-loop-helix fusion proteins of Tal and E47

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JOURNAL OF PEPTIDE RESEARCH 2001年第5期57卷 354-360页

作者： Ghosh, I Bishop, P Chmielewski, J Purdue Univ Dept Chem W Lafayette IN 47907 USA

The basic helix-loop-helix (bHLH) transcription factor Tal has been shown to form heterodimers with the ubiquitously expressed bHLH transcription factor E47 and thereby modulate gene expression. The absence of homodimeric Tal-DNA complexes had been attributed to the inability of Tal to homodimerize, but subsequent studies have shown that the bHLH region of Tar does homodimerize. In order to correlate the contributions of both the basic region and the helix-loop-helix (HLH) domain to the lack of DNA binding by Tal homodimers, mutant and fusion proteins based on Tal and E47 were designed and synthesized. Size-exclusion chromatography established that all mutant and fusion proteins were dimeric. Point mutations were made within the basic region of Tal based on residues within E47 that are essential for DNA binding, but an affinity for DNA was not observed. Even complete replacement of the basic region in Tal with the basic region of E47, in an E47-Tal fusion protein, did not confer DNA binding upon the protein. However, when the dimerization domain in Tal was replaced with its E47 counterpart, in a Tal-E47 fusion protein, sequence specific DNA binding was observed with an apparent dissociation constant of 3.6x10(-9) M-2. Furthermore, circular dichroism studies showed that the basic region of Tal in the Tal-E47 fusion protein underwent a random coil to helix transition in the presence of a specific DNA probe. These experimental observations indicate that the inability of Tal homodimers to recognize DNA stems from a misalignment of its basic region with respect to the HLH domain, rather than an intrinsic inability of the Tal basic region to bind DNA.

关键词： basic helix-loop-helix dimerization DNA binding E47 fusion proteins Tal transcription factor

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Differential cooperation between dHAND and three different E-proteins

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BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 2004年第1期323卷 168-174页

作者： Murakami, M Kataoka, K Tominaga, J Nakagawa, O Kurihara, H Kumamoto Univ Inst Mol Embryol & Genet Dept Embryogenesis Div Integrat Cell Biol Kumamoto 8600811 Japan Univ Texas SW Med Ctr Dept Mol Biol Dallas TX 75390 USA Univ Tokyo Grad Sch Med Dept Physiol Chem & Metab Bunkyo Ku Tokyo 1130033 Japan

dHAND is a transcription factor belonging to the class B basic helix-loop-helix protein family and is expressed during embryogenesis in the heart, branchial arches, limb buds, and neural crest derivatives. Despite much study, the molecular mechanisms involved in the regulation of dHAND activity are not well understood. We therefore carried out yeast two-hybrid screening using full-length dHAND as bait, which led to identification of several dHAND-binding proteins, including three E-proteins: E2A, ME2, and ALF1 Subsequent analysis revealed that although their heterodimerization and transcriptional activities were similar, dHAND/ E-protein heterodimers bind to an E-box element with differing affinities, suggesting they have distinct DNA binding specificities. Moreover, in situ hybridization showed that E-protein genes are expressed fairly ubiquitously among embryonic tissues, including the branchial arches and limb buds. By contrast, little signal was detected in the heart, suggesting that dHAND complexes with partners other than E-proteins in cardiac tissue. (C) 2004 Elsevier Inc. All rights reserved.

关键词： dHAND E-protein basic helix-loop-helix transcription factor embryogenesis

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Phyllopod is a target gene of proneural proteins in Drosophila external sensory organ development

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2004年第22期101卷 8378-8383页

作者： Pi, HW Huang, SK Tang, CY Sun, YH Chien, CT Acad Sinica Inst Mol Biol Taipei 115 Taiwan

Proneural basic helix-loop-helix (bHLH) proteins initiate neurogenesis in both vertebrates and invertebrates. The Drosophila Achaete (Ac) and Scute (Sc) proteins are among the first identified members of the large bHLH proneural protein family. phyllopod (phyl), encoding an ubiquitin ligase adaptor, is required for ac- and sc-dependent external sensory (ES) organ development. Expression of phyl is directly activated by Ac and Sc. Forced expression of phyl rescues ES organ formation in ac and sc double mutants. phyl and senseless, encoding a Zn-finger transcriptional factor, depend on each other in ES organ development. Our results provide the first example that bHLH proneural proteins promote neurogenesis through regulation of protein degradation.

关键词： E3 ligase senseless basic helix-loop-helix neurogenesis

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Mist1 is necessary for the establishment of granule organization in serous exocrine cells of the gastrointestinal tract

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MECHANISMS OF DEVELOPMENT 2004年第3期121卷 261-272页

作者： Johnson, CL Kowalik, AS Rajakumar, N Pin, CL Univ Western Ontario Dept Paediat Child Hlth Res Inst London ON N6C 2V5 Canada Univ Western Ontario Dept Physiol & Pharmacol Child Hlth Res Inst London ON N6C 2V5 Canada Univ Western Ontario Dept Psychiat London ON N6C 2V5 Canada

Establishing a pool of granules at the luminal border is a key step during exocrine cell development in the pancreas and is necessary for efficient release of digestive enzymes through regulated exocytosis. Several proteins have been linked to maintaining granule organization, but it is unclear which regulatory mechanisms are necessary to establish organization. Based on temporal and spatial expression, the transcription factor Mist1 is an excellent candidate, and analysis of mice that do not express Mist1 (Mist1(KO)) reveal disrupted cell morphology in adult pancreatic acini. To address Mist1's role in establishing granule location, we have characterized the organization of pancreatic acini throughout development in Mist1(KO) mice. Using various histological approaches, we have determined that correct granule organization is never established in pancreatic acini of Mist1(KO) mice. Further examination indicates that this disruption in granule targeting may be the primary defect in MiSt1(KO) mice as granule organization is affected in other serous exocrine cells that normally express Mist1. To identify a mechanistic link between granule targeting and the loss of Mist1 function, intercellular junctions and the expression of RabD were assessed. While both of these factors are affected in Mist1(KO) mice, these changes alone do not account for the disorganization observed in MiStl(KO) tissues. Therefore, we conclude that Mist1 is necessary for complete differentiation and maturation of serous exocrine cells through the combined regulation of several exocrine specific genes. (C) 2004 Elsevier Ireland Ltd. All rights reserved.

关键词： regulated exocytosis pancreatic development basic helix-loop-helix Rab3D

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NEUROD1 acts in vitro as an upstream regulator of NEUROD2 in trophoblast cells

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BIOCHIMICA ET BIOPHYSICA ACTA-GENE STRUCTURE AND EXPRESSION 2004年第1期1676卷 96-103页

作者： Westerman, BA Chhatta, A Poutsma, A van Vegchel, T Oudejans, CBM Vrije Univ Amsterdam Med Ctr Dept Clin Chem Mol Biol Lab NL-1081 HV Amsterdam Netherlands

The basic helix-loop-helix (bHLH) transcription factors NEUROD1, NEUROD2 and ATH2 are expressed during first trimester human placental development. We determined the transactivation potential of each of these factors in trophoblasts by measuring changes in the endogenous gene activity using absolute quantification by real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) after transient transfection. In these assays, NEUROD1 was found to transiently transactivate NEUROD2 in trophoblast cells. Promotor truncation assays, using luciferase constructs, showed the presence of two domains in the NEUROD2 promotor, which showed increased activity after NeuroD1 transfection. Each of these NeuroD1-responsive domains contains an E-box sequence. The NEUROD2 transactivation data fit with the spatial expression pattern of NEUROD1 and NEUROD2, since they are expressed in endovascular trophoblasts. This expression pattern, as well as the present transactivation results, might suggest the presence of a NEUROD differentiation cascade during first trimester human placental development. (C) 2003 Elsevier B.V. All rights reserved.

关键词： basic helix-loop-helix transcription factor NEUROD1 NEUROD2 ATH2 ASCL2 endovascular extravillous trophoblast

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NeuroD: The predicted and the surprising

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MOLECULES AND CELLS 2004年第3期18卷 271-288页

作者： Chae, JH Stein, GH Lee, JE Univ Colorado Dept Mol Cellular & Dev Biol Boulder CO 80309 USA

NeuroD (otherwise known as BETA2) is a basic helix-loop-helix (bHLH) transcription factor that is capable of converting embryonic epidermal cells into fully differentiated neurons in Xenopus embryos. In insulinoma cells, NeuroD can bind and activate the insulin promoter. When NeuroD is deleted in mice, the early differentiating pancreatic endocrine cells and a subset of the neurons in the central and peripheral nervous systems die, resulting in cellular deficits in the pancreatic islets, cerebellum, hippocampus and inner ear sensory ganglia. As a consequence, mice become diabetic and display neurological defects including ataxia and deafness. These gain-of-function and loss-of-function phenotypes suggest that NeuroD controls both common and distinct sets of molecules involved in cell survival and differentiation in different tissue types. In this review, we examine what is known about NeuroD and what remains to be answered. Understanding the primary function of NeuroD will be extremely valuable in the diagnosis and cure of the diseases that involve this transcription factor, which plays essential roles in the development and function of the pancreas and the nervous system.

关键词： ataxia basic helix-loop-helix BETA2 bHLH diabetes deafness NeuroD neurogenesis

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Induction of transcripts derived from promoter III of the acetyl-CoA carboxylase-α gene in mammary gland is associated with recruitment of SREBP-1 to a region of the proximal promoter defined by a DNase I hypersensitive site

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BIOCHEMICAL JOURNAL 2003年第2期375卷 489-501页

作者： Barber, MC Vallance, AJ Kennedy, HT Travers, MT Hannah Res Inst Ayr KA6 5HL Scotland

ACC-alpha (acetyl-CoA carboxylase-alpha), a key regulator of fatty-acid metabolism, is encoded by mRNAs transcribed from three promoters, PI, PII and PIII, in the ovine genome. Enhanced expression of transcripts encoded by PIII in mammary gland during lactation is associated with alterations in chromatin structure that result in the detection of two DNase I hypersensitive sites, upstream of the start site. The most proximal site, located between - 190 and - 10, is characterized by the presence of an inverted-CCAAT box, C2 at - 167, and E-boxes, E1 and E2, at - 151 and - 46. Deletion of these motifs, which bind nuclear factor-Y and upstream stimulatory factors respectively in gel-shift assays, attenuates the activity of luciferase reporter constructs in transfected cells. Chromatin immunoprecipitation demonstrated that these transcription factors were associated with PIII in vivo in both lactating and non-lactating mammary tissues. The basic helix-loop-helix-leucine zipper transcription factor, SREBP-1 (sterol-regulated-element-binding protein-1), transactivated PIII reporter constructs in transfected HClI mammary cells, and this was dependent on the presence of El, but not on C2 or E2. SREBP-1 was only associated with PIII in chromatin from lactating animals, which was coincident with a 4-fold increase in the precursor (125 kDa) form of SREBP-1 in microsomes and the appearance of the mature form (68 kDa) in the nucleus. SREBP-1 motifs are also present in the proximal region of PII, which is also induced in lactation. This indicates that SREBP-1 is a major developmental regulator of the programme of lipid synthesis de novo in the lactating mammary gland.

关键词： basic helix-loop-helix chromatin immunoprecipitation lactation lipogenesis STAT5

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