scholarly journals Targeting the Microphthalmia Basic Helix-Loop-Helix–Leucine Zipper Transcription Factor to a Subset of E-Box Elements In Vitro and In Vivo

1998 ◽  
Vol 18 (12) ◽  
pp. 6930-6938 ◽  
Author(s):  
I. Aksan ◽  
C. R. Goding
Keyword(s):  
Transcription Factor ◽  
Leucine Zipper ◽  
Pigment Cells ◽  
Specific Gene ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
P Gene ◽  
E Box

ABSTRACT The development of melanocytes, which are pigment-producing cells responsible for skin, hair, and eye color, is absolutely dependent on the action of the microphthalmia basic helix-loop-helix–leucine zipper (bHLH-LZ) transcription factor (Mi); mice lacking a functional Mi protein are entirely devoid of pigment cells. Mi has been shown to activate transcription of the tyrosinase,TRP-1, TRP-2, and QNR-71 genes through specific E-box elements, most notably the highly conserved M box. We investigated the mechanism which enables Mi to be recruited specifically to a restricted subset of E boxes in target promoters while being prevented from binding E-box elements in other promoters. We show both in vitro and in vivo that the presence of a T residue flanking a CATGTG E box is an essential determinant of the ability of Mi to bind DNA, and we successfully predict that the CATGTG E box from the P gene would not bind Mi. In contrast, no specific requirement for the sequences flanking a CACGTG E box was observed, and no binding to an atypical E box in the c-Kit promoter was detected. The relevance of these observations to the control of melanocyte-specific gene expression was highlighted by the fact that the E-box elements located in thetyrosinase, TRP-1, TRP-2, andQNR-71 promoters without exception possess a 5′ flanking T residue which is entirely conserved between species as diverse as man and turtle. The ability of Mi to discriminate between different E-box motifs provides a mechanism to restrict the repertoire of genes which are likely to be regulated by Mi and provides insight into the ability of bHLH-LZ transcription factors to achieve the specificity required for the precise coordination of transcription during development.

scholarly journals 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 ◽  
1997 ◽  
Vol 90 (10) ◽  
pp. 3984-3995 ◽  
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.

scholarly journals Orphan Nuclear Receptor Small Heterodimer Partner, a Novel Corepressor for a Basic Helix-Loop-Helix Transcription Factor BETA2/NeuroD

2004 ◽  
Vol 18 (4) ◽  
pp. 776-790 ◽  
Author(s):  
Joon-Young Kim ◽  
Khoi Chu ◽  
Han-Jong Kim ◽  
Hyun-A Seong ◽  
Ki-Cheol Park ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Nuclear Receptor ◽  
Transcriptional Activity ◽  
Orphan Nuclear Receptor ◽  
Small Heterodimer Partner ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
Coactivator P300

Abstract Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor that lacks a conventional DNA binding domain (DBD) and represses the transcriptional activity of various nuclear receptors. In this study, we examined the novel cross talk between SHP and BETA2/NeuroD, a basic helix-loop-helix transcription factor. In vitro and in vivo protein interaction studies showed that SHP physically interacts with BETA2/NeuroD, but not its heterodimer partner E47. Moreover, confocal microscopic study and immunostaining results demonstrated that SHP colocalized with BETA2 in islets of mouse pancreas. SHP inhibited BETA2/NeuroD-dependent transactivation of an E-box reporter, whereas SHP was unable to repress the E47-mediated transactivation and the E-box mutant reporter activity. In addition, SHP repressed the BETA2-dependent activity of glucokinase and cyclin-dependent kinase inhibitor p21 gene promoters. Gel shift and in vitro protein competition assays indicated that SHP inhibits neither dimerization nor DNA binding of BETA2 and E47. Rather, SHP directly repressed BETA2 transcriptional activity and p300-enhanced BETA2/NeuroD transcriptional activity by inhibiting interaction between BETA2 and coactivator p300. We also showed that C-terminal repression domain within SHP is also required for BETA2 repression. However, inhibition of BETA2 activity was not observed by naturally occurring human SHP mutants that cannot interact with BETA2/NeuroD. Taken together, these results suggest that SHP acts as a novel corepressor for basic helix-loop-helix transcription factor BETA2/NeuroD by competing with coactivator p300 for binding to BETA2/NeuroD and by its direct transcriptional repression function.

scholarly journals Selective utilization of basic helix-loop-helix-leucine zipper proteins at the immunoglobulin heavy-chain enhancer.

1997 ◽  
Vol 17 (1) ◽  
pp. 18-23 ◽  
Author(s):  
R S Carter ◽  
P Ordentlich ◽  
T Kadesch
Keyword(s):  
Heavy Chain ◽  
Leucine Zipper ◽  
Physiological Role ◽  
Immunoglobulin Heavy Chain ◽  
Dominant Negative ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
Derivatives Of

The microE3 E box within the immunoglobulin heavy-chain (IgH) enhancer binds several proteins of the basic helix-loop-helix-leucine zipper (bHLHzip) class, including TFE3, USF1, and Max. Both TFE3 and USF have been described as transcriptional activators, and so we investigated their possible roles in activating the IgH enhancer in vivo. Although TFE3 activated various enhancer-based reporters, both USF1 and Max effectively inhibited transcription. Inhibition by USF correlated with the lack of a strong activation domain and was the result of the protein neutralizing the microE3 site. The effects of dominant-negative derivatives of TFE3 and USF1 confirmed that TFE3, or a TFE3-like protein, is the primary cellular bHLHzip protein that activates the IgH enhancer. In addition to providing a physiological role for TFE3, our results call into question the traditional view of USF1 as an obligate transcriptional activator.

scholarly journals Transcription factor Etv6 regulates functional differentiation of cross-presenting classical dendritic cells

2018 ◽  
Vol 215 (9) ◽  
pp. 2265-2278 ◽  
Author(s):  
Colleen M. Lau ◽  
Ioanna Tiniakou ◽  
Oriana A. Perez ◽  
Margaret E. Kirkling ◽  
George S. Yap ◽  
...  
Keyword(s):  
T Cells ◽  
Dendritic Cells ◽  
Transcription Factor ◽  
T Cell ◽  
Cd8 T Cells ◽  
Functional Differentiation ◽  
Specific Gene ◽  
Hematopoietic Stem

An IRF8-dependent subset of conventional dendritic cells (cDCs), termed cDC1, effectively cross-primes CD8+ T cells and facilitates tumor-specific T cell responses. Etv6 is an ETS family transcription factor that controls hematopoietic stem and progenitor cell (HSPC) function and thrombopoiesis. We report that like HSPCs, cDCs express Etv6, but not its antagonist, ETS1, whereas interferon-producing plasmacytoid dendritic cells (pDCs) express both factors. Deletion of Etv6 in the bone marrow impaired the generation of cDC1-like cells in vitro and abolished the expression of signature marker CD8α on cDC1 in vivo. Moreover, Etv6-deficient primary cDC1 showed a partial reduction of cDC-specific and cDC1-specific gene expression and chromatin signatures and an aberrant up-regulation of pDC-specific signatures. Accordingly, DC-specific Etv6 deletion impaired CD8+ T cell cross-priming and the generation of tumor antigen–specific CD8+ T cells. Thus, Etv6 optimizes the resolution of cDC1 and pDC expression programs and the functional fitness of cDC1, thereby facilitating T cell cross-priming and tumor-specific responses.

Hxt encodes a basic helix-loop-helix transcription factor that regulates trophoblast cell development

Development ◽  
1995 ◽  
Vol 121 (8) ◽  
pp. 2513-2523 ◽  
Author(s):  
J.C. Cross ◽  
M.L. Flannery ◽  
M.A. Blanar ◽  
E. Steingrimsson ◽  
N.A. Jenkins ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Gene Promoter ◽  
Giant Cells ◽  
Placental Lactogen ◽  
Specific Gene ◽  
Bhlh Transcription Factor ◽  
Trophoblast Cells ◽  
Positive Role ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix

Trophoblast cells are the first lineage to form in the mammalian conceptus and mediate the process of implantation. We report the cloning of a basic helix-loop-helix (bHLH) transcription factor gene, Hxt, that is expressed in early trophoblast and in differentiated giant cells. A separate gene, Hed, encodes a related protein that is expressed in maternal deciduum surrounding the implantation site. Overexpression of Hxt in mouse blastomeres directed their development into trophoblast cells in blastocysts. In addition, overexpression of Hxt induced the differentiation of rat trophoblast (Rcho-1) stem cells as assayed by changes in cell adhesion and by activation of the placental lactogen-I gene promoter, a trophoblast giant cell-specific gene. In contrast, the negative HLH regulator, Id-1, inhibited Rcho-1 differentiation and placental lactogen-I transcription. These data demonstrate a role for HLH factors in regulating trophoblast development and indicate a positive role for Hxt in promoting the formation of trophoblast giant cells.

NeuroM, a neural helix-loop-helix transcription factor, defines a new transition stage in neurogenesis

Development ◽  
1997 ◽  
Vol 124 (17) ◽  
pp. 3263-3272 ◽  
Author(s):  
T. Roztocil ◽  
L. Matter-Sadzinski ◽  
C. Alliod ◽  
M. Ballivet ◽  
J.M. Matter
Keyword(s):  
Nervous System ◽  
Transcription Factor ◽  
Mitotic Cycle ◽  
Ventricular Zone ◽  
Helix Loop Helix ◽  
E Box ◽  
Genes Encoding ◽  
Developing Nervous System

Genes encoding transcription factors of the helix-loop-helix family are essential for the development of the nervous system in Drosophila and vertebrates. Screens of an embryonic chick neural cDNA library have yielded NeuroM, a novel neural-specific helix-loop-helix transcription factor related to the Drosophila proneural gene atonal. The NeuroM protein most closely resembles the vertebrate NeuroD and Nex1/MATH2 factors, and is capable of transactivating an E-box promoter in vivo. In situ hybridization studies have been conducted, in conjunction with pulse-labeling of S-phase nuclei, to compare NeuroM to NeuroD expression in the developing nervous system. In spinal cord and optic tectum, NeuroM expression precedes that of NeuroD. It is transient and restricted to cells lining the ventricular zone that have ceased proliferating but have not yet begun to migrate into the outer layers. In retina, NeuroM is also transiently expressed in cells as they withdraw from the mitotic cycle, but persists in horizontal and bipolar neurons until full differentiation, assuming an expression pattern exactly complementary to NeuroD. In the peripheral nervous system, NeuroM expression closely follows cell proliferation, suggesting that it intervenes at a similar developmental juncture in all parts of the nervous system. We propose that availability of the NeuroM helix-loop-helix factor defines a new stage in neurogenesis, at the transition between undifferentiated, premigratory and differentiating, migratory neural precursors.

The Basic Helix-Loop-Helix TAL1/SCL and Its Partners E47 and LMO2 Act Upstream of the VE-Cadherin Gene in Endothelial Cells.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1795-1795
Author(s):  
Virginie Deleuze ◽  
Elias Chalhoub ◽  
Rawan El-Hajj ◽  
Christiane Dohet ◽  
Mikael Le Clech ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Ectopic Expression ◽  
Cell Junctions ◽  
Small Interfering Rnas ◽  
Hek 293 ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Cell Cell

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.

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

2000 ◽  
Vol 20 (23) ◽  
pp. 8845-8854 ◽  
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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