The transcriptional coactivator P300 functionally associates with the basic helix loop helix protein, beta2 in vivo to activate transcription of the secretin gene

Abstract The basic helix-loop-helix protein TAL-1/SCL, essential for the formation of the hematopoietic system, is also required for vascular development and more particularly for embryonic angiogenesis. We previously reported that TAL-1 acts as a positive factor for post-natal angiogenesis by stimulating endothelial morphogenesis. To understand how TAL-1 modulates angiogenesis, we investigated the functional consequences of TAL-1 silencing, mediated by small-interfering RNAs, in human primary endothelial cells (ECs). We found that TAL-1 knockdown impaired in vitro EC tubulomorphogenesis (in 2-D on Matrigel or 3-D in collagen I gel), with the notable absence of cell-cell contacts, a prerequisite for morphogenesis initiation. This cellular deficiency was associated with a dramatic reduction in the vascular-endothelial (VE)-cadherin at intercellular junctions, the major component of endothelial adherens junctions. In contrast, PECAM (or CD31) was present at cell-cell junctions at the same levels as control cells. Importantly, silencing of two known TAL-1-partners in hematopoietic cells, E47 or LMO2, produce the same effects as TAL-1. Accordingly, silencing of TAL-1, as well as E47 and LMO2, provoked down-regulation of VE-cadherin at both the mRNA and protein levels. Transient transfection experiments in HUVECs showed that TAL-1 and E47 regulate the VE-cadherin promoter through a specialized E-box element. Finally, endogenous VE-cadherin transcription could be directly activated in non-endothelial HEK-293 cells that neither express TAL-1 or LMO2, by the sole concomitant ectopic expression of TAL-1, E47 and LMO2. Overall, our data demonstrate that a multiprotein complex containing at least TAL-1, LMO2 and E47 act upstream of the VE-cadherin gene. We are currently performing chromatin immunoprecipitation (ChIP) to investigate whether the TAL-1-containing complex binds in vivo the VE-cadherin promoter. This study identifies VE-cadherin as an upstream TAL-1-target gene in the endothelial lineage, and provides a first clue in TAL-1 function in the control of angiogenesis.

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MondoA, a Novel Basic Helix-Loop-Helix–Leucine Zipper Transcriptional Activator That Constitutes a Positive Branch of a Max-Like Network

Molecular and Cellular Biology ◽

10.1128/mcb.20.23.8845-8854.2000 ◽

2000 ◽

Vol 20 (23) ◽

pp. 8845-8854 ◽

Cited By ~ 77

Author(s):

Andrew N. Billin ◽

Alanna L. Eilers ◽

Kathryn L. Coulter ◽

Jennifer S. Logan ◽

Donald E. Ayer

Keyword(s):

Transcriptional Activation ◽

Nuclear Export ◽

Mammalian Cells ◽

Leucine Zipper ◽

Functional Characterization ◽

Nuclear Accumulation ◽

Cytoplasmic Localization ◽

Basic Helix Loop Helix ◽

Helix Loop Helix

ABSTRACT Max is a common dimerization partner for a family of transcription factors (Myc, Mad [or Mxi]), and Mnt [or Rox] proteins) that regulate cell growth, proliferation, and apoptosis. We recently characterized a novel Max-like protein, Mlx, which interacts with Mad1 and Mad4. Here we describe the cloning and functional characterization of a new family of basic helix-loop-helix–leucine zipper heterodimeric partners for Mlx termed the Mondo family. MondoA forms homodimers weakly and does not interact with Max or members of the Myc or Mad families. MondoA and Mlx associate in vivo, and surprisingly, they are localized primarily to the cytoplasm of cultured mammalian cells. Treatment of cells with the nuclear export inhibitor leptomycin B results in the nuclear accumulation of MondoA and Mlx, demonstrating that they shuttle between the cytoplasmic and nuclear compartments rather than having exclusively cytoplasmic localization. MondoA preferentially forms heterodimers with Mlx, and this heterocomplex can bind to, and activate transcription from, CACGTG E-boxes when targeted to the nucleus via a heterologous nuclear localization signal. The amino termini of the Mondo proteins are highly conserved among family members and contain separable and autonomous cytoplasmic localization and transcription activation domains. Therefore, Mlx can mediate transcriptional repression in conjunction with the Mad family and can mediate transcriptional activation via the Mondo family. We propose that Mlx, like Max, functions as the center of a transcription factor network.

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Transcription factor Tcf4 is the preferred heterodimerization partner for Olig2 in oligodendrocytes and required for differentiation

Nucleic Acids Research ◽

10.1093/nar/gkaa218 ◽

2020 ◽

Vol 48 (9) ◽

pp. 4839-4857 ◽

Cited By ~ 4

Author(s):

Miriam Wedel ◽

Franziska Fröb ◽

Olga Elsesser ◽

Marie-Theres Wittmann ◽

D Chichung Lie ◽

...

Keyword(s):

Ex Vivo ◽

Physical Interaction ◽

Functional Studies ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

Mouse Mutants ◽

Id Proteins ◽

A Cell ◽

Oligodendrocyte Development

Abstract Development of oligodendrocytes and myelin formation in the vertebrate central nervous system is under control of several basic helix-loop-helix transcription factors such as Olig2, Ascl1, Hes5 and the Id proteins. The class I basic helix-loop-helix proteins Tcf3, Tcf4 and Tcf12 represent potential heterodimerization partners and functional modulators for all, but have not been investigated in oligodendrocytes so far. Using mouse mutants, organotypic slice and primary cell cultures we here show that Tcf4 is required in a cell-autonomous manner for proper terminal differentiation and myelination in vivo and ex vivo. Partial compensation is provided by the paralogous Tcf3, but not Tcf12. On the mechanistic level Tcf4 was identified as the preferred heterodimerization partner of the central regulator of oligodendrocyte development Olig2. Both genetic studies in the mouse as well as functional studies on enhancer regions of myelin genes confirmed the relevance of this physical interaction for oligodendrocyte differentiation. Considering that alterations in TCF4 are associated with syndromic and non-syndromic forms of intellectual disability, schizophrenia and autism in humans, our findings point to the possibility of an oligodendroglial contribution to these disorders.

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PU.1/Pip and Basic Helix Loop Helix Zipper Transcription Factors Interact With Binding Sites in the CD20 Promoter to Help Confer Lineage- and Stage-Specific Expression of CD20 in B Lymphocytes

Blood ◽

10.1182/blood.v90.10.3984 ◽

1997 ◽

Vol 90 (10) ◽

pp. 3984-3995 ◽

Cited By ~ 60

Author(s):

Andreas Himmelmann ◽

Agostino Riva ◽

Gaye Lynn Wilson ◽

Brian P. Lucas ◽

Claire Thevenin ◽

...

Keyword(s):

B Cell ◽

Plasma Cells ◽

Expression Vectors ◽

Specific Gene ◽

Cell Stage ◽

Specific Expression ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

E Box

Abstract CD20 is a B-lineage–specific gene expressed at the pre–B-cell stage of B-cell development that disappears on differentiation to plasma cells. As such, it serves as an excellent paradigm for the study of lineage and developmental stage-specific gene expression. Using in vivo footprinting we identified two sites in the promoter at −45 and −160 that were occupied only in CD20+ B cells. The −45 site is an E box that binds basic helix-loop-helix-zipper proteins whereas the −160 site is a composite PU.1 and Pip binding site. Transfection studies with reporter constructs and various expression vectors verified the importance of these sites. The composite PU.1 and Pip site likely accounts for both lineage and stage-specific expression of CD20 whereas the CD20 E box binding proteins enhance overall promoter activity and may link the promoter to a distant enhancer.

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Misexpression of basic helix-loop-helix genes in the murine cerebral cortex affects cell fate choices and neuronal survival

Development ◽

10.1242/dev.127.14.3021 ◽

2000 ◽

Vol 127 (14) ◽

pp. 3021-3030 ◽

Cited By ~ 5

Author(s):

L. Cai ◽

E.M. Morrow ◽

C.L. Cepko

Keyword(s):

Cerebral Cortex ◽

Cell Fate ◽

Neuronal Survival ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

Bhlh Genes ◽

Infected Cells ◽

Glial Fate

To investigate the role(s) of basic helix-loop-helix genes (bHLH) genes in the developing murine cerebral cortex, Mash1, Math2, Math3, Neurogenin1 (Ngn1), Ngn2, NeuroD, NeuroD2 and Id1 were transduced in vivo into the embryonic and postnatal cerebral cortex using retrovirus vectors. The morphology and location of infected cells were analyzed at postnatal stages. The data indicate that a subset of bHLH genes are capable of regulating the choice of neuronal versus glial fate and that, when misexpressed, they can be deleterious to the survival of differentiating neurons, but not glia.

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The Basic Helix-Loop-Helix Transcription Factor NeuroD1 Facilitates Interaction of Sp1 with the Secretin Gene Enhancer

Molecular and Cellular Biology ◽

10.1128/mcb.00438-07 ◽

2007 ◽

Vol 27 (22) ◽

pp. 7839-7847 ◽

Cited By ~ 18

Author(s):

Subir K. Ray ◽

Andrew B. Leiter

Keyword(s):

Transcription Factor ◽

Dna Binding ◽

Target Genes ◽

Zinc Fingers ◽

Homeodomain Proteins ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

Gene Enhancer ◽

Genes Encoding

ABSTRACT The basic helix-loop-helix transcription factor NeuroD1 is required for late events in neuronal differentiation, for maturation of pancreatic β cells, and for terminal differentiation of enteroendocrine cells expressing the hormone secretin. NeuroD1-null mice demonstrated that this protein is essential for expression of the secretin gene in the murine intestine, and yet it is a relatively weak transcriptional activator by itself. The present study shows that Sp1 and NeuroD1 synergistically activate transcription of the secretin gene. NeuroD1, but not its widely expressed dimerization partner E12, physically interacts with the C-terminal 167 amino acids of Sp1, which include its DNA binding zinc fingers. NeuroD1 stabilizes Sp1 DNA binding to an adjacent Sp1 binding site on the promoter to generate a higher-order DNA-protein complex containing both proteins and facilitates Sp1 occupancy of the secretin promoter in vivo. NeuroD-dependent transcription of the genes encoding the hormones insulin and proopiomelanocortin is potentiated by lineage-specific homeodomain proteins. The stabilization of binding of the widely expressed transcription factor Sp1 to the secretin promoter by NeuroD represents a distinct mechanism from other NeuroD target genes for increasing NeuroD-dependent transcription.

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The basic-helix-loop-helix protein pod1 is critically important for kidney and lung organogenesis

Development ◽

10.1242/dev.126.24.5771 ◽

1999 ◽

Vol 126 (24) ◽

pp. 5771-5783 ◽

Cited By ~ 19

Author(s):

S.E. Quaggin ◽

L. Schwartz ◽

S. Cui ◽

P. Igarashi ◽

J. Deimling ◽

...

Keyword(s):

Transcription Factor ◽

Molecular Mechanisms ◽

Cell Types ◽

Perinatal Period ◽

Branching Morphogenesis ◽

Bhlh Transcription Factor ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

Kidney Morphogenesis

Epithelial-mesenchymal interactions are required for the development of all solid organs but few molecular mechanisms that underlie these interactions have been identified. Pod1 is a basic-helix-loop-helix (bHLH) transcription factor that is highly expressed in the mesenchyme of developing organs that include the lung, kidney, gut and heart and in glomerular visceral epithelial cells (podocytes). To determine the function of Pod1 in vivo, we have generated a lacZ-expressing null Pod1 allele. Null mutant mice are born but die in the perinatal period with severely hypoplastic lungs and kidneys that lack alveoli and mature glomeruli. Although Pod1 is exclusively expressed in the mesenchyme and podocytes, major defects are observed in the adjacent epithelia and include abnormalities in epithelial differentiation and branching morphogenesis. Pod1 therefore appears to be essential for regulating properties of the mesenchyme that are critically important for lung and kidney morphogenesis. Defects specific to later specialized cell types where Pod1 is expressed, such as the podocytes, were also observed, suggesting that this transcription factor may play multiple roles in kidney morphogenesis.

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Regulation of neurogenesis by interactions between HEN1 and neuronal LMO proteins

Development ◽

10.1242/dev.127.2.425 ◽

2000 ◽

Vol 127 (2) ◽

pp. 425-435 ◽

Cited By ~ 2

Author(s):

J. Bao ◽

D.A. Talmage ◽

L.W. Role ◽

J. Gautier

Keyword(s):

Neuronal Differentiation ◽

Transcriptional Activity ◽

Expression Patterns ◽

Dorsal Side ◽

Neural Plate ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

Human Genes ◽

Early Neurogenesis

Basic-helix-loop-helix transcription factors regulate neurogenesis and neuronal differentiation by as yet unknown mechanisms. We show that an embryonic neuronal-specific basic-helix-loop-helix protein, HEN1 (also known as NSCL1 or NHLH), interacts with ‘LIM only’ proteins. Examination of the expression patterns of XHEN1 and XLMO-3, the Xenopus homologues of these human genes, reveals extensive overlap during early neurogenesis: at the onset of gastrulation on the dorsal side of the blastopore lip and, subsequently, in the prospective neural plate. Binding of XLMO-3 increases the transcriptional activity of XHEN1 in vivo. Co-expression of these two genes in Xenopus embryos induces a cascade of expression of neuronal-specific basic-helix-loop-helix proteins that leads to neuronal differentiation. We propose that XHEN1, in concert with XLMO-3, is a critical regulator of neurogenesis.

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The Drosophila Basic Helix-Loop-Helix Protein DIMMED Directly Activates PHM, a Gene Encoding a Neuropeptide-Amidating Enzyme

Molecular and Cellular Biology ◽

10.1128/mcb.01104-07 ◽

2007 ◽

Vol 28 (1) ◽

pp. 410-421 ◽

Cited By ~ 43

Author(s):

Dongkook Park ◽

Orie T. Shafer ◽

Stacie P. Shepherd ◽

Hyunsuk Suh ◽

Jennifer S. Trigg ◽

...

Keyword(s):

Cell Fate ◽

Transcriptional Activation ◽

Regulatory Region ◽

Total Activity ◽

Bhlh Protein ◽

Hek 293 ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

E Boxes

ABSTRACT The basic helix-loop-helix (bHLH) protein DIMMED (DIMM) supports the differentiation of secretory properties in numerous peptidergic cells of Drosophila melanogaster. DIMM is coexpressed with diverse amidated neuropeptides and with the amidating enzyme peptidylglycine α-hydroxylating monooxygenase (PHM) in approximately 300 cells of the late embryo. Here we confirm that DIMM has transcription factor activity in transfected HEK 293 cells and that the PHM gene is a direct target. The mammalian DIMM orthologue MIST1 also transactivated the PHM gene. DIMM activity was dependent on the basic region of the protein and on the sequences of three E-box sites within PHM's first intron; the sites make different contributions to the total activity. These data suggest a model whereby the three E boxes interact cooperatively and independently to produce high PHM transcriptional activation. This DIMM-controlled PHM regulatory region displayed similar properties in vivo. Spatially, its expression mirrored that of the DIMM protein, and its activity was largely dependent on dimm. Further, in vivo expression was highly dependent on the sequences of the same three E boxes. This study supports the hypothesis that DIMM is a master regulator of a peptidergic cell fate in Drosophila and provides a detailed transcriptional mechanism of DIMM action on a defined target gene.

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