scholarly journals Extramacrochaete promotes branch and bouton number via the sequestration of Daughterless in the cytoplasm of neurons

2019 ◽  
Author(s):  
Edward A. Waddell ◽  
Jennifer M. Viveiros ◽  
Erin L. Robinson ◽  
Michal A. Sharoni ◽  
Nina K. Latcheva ◽  
...  
Keyword(s):  
Class I ◽  
Bhlh Protein ◽  
Tissue Specific ◽  
Consensus Sequences ◽  
Helix Loop Helix ◽  
Molecular Logic ◽  
E Box ◽  
Mature Neurons ◽  
Type V ◽  
Bhlh Proteins

AbstractThe class I basic Helix Loop Helix (bHLH) proteins are highly conserved transcription factors that are ubiquitously expressed. A wealth of literature on class I bHLH proteins have shown that these proteins must homodimerize or heterodimerize with tissue specific HLH proteins in order to bind DNA at E box (CANNTG) consensus sequences to control tissue specific transcription. Due to its ubiquitous expression, class I bHLH proteins are also extensively regulated post-translationally, mostly through dimerization. Previously, we reported that in addition to its role in promoting neurogenesis, the class I bHLH protein Daughterless also functions in mature neurons to restrict axon branching and synapse number. Here, we show that part of the molecular logic that specifies how Daughterless functions in neurogenesis is also conserved in neurons. We show that the type V HLH protein Extramacrochaete binds to and represses Daughterless function by sequestering Daughterless to the cytoplasm. This work provides initial insights into the mechanisms underlying the function of Daughterless and Extramacrochatae in neurons while providing a novel understanding of how Extramacrochaetae functions to restricts Daughterless activity within the cell.

scholarly journals Displacement of an E-box-binding repressor by basic helix-loop-helix proteins: implications for B-cell specificity of the immunoglobulin heavy-chain enhancer.

1994 ◽  
Vol 14 (9) ◽  
pp. 6153-6163 ◽  
Author(s):  
T Genetta ◽  
D Ruezinsky ◽  
T Kadesch
Keyword(s):  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Zinc Finger Protein ◽  
Immunoglobulin Heavy Chain ◽  
Bhlh Protein ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
Bhlh Proteins

The activity of the immunoglobulin heavy-chain (IgH) enhancer is restricted to B cells, although it binds both B-cell-restricted and ubiquitous transcription factors. Activation of the enhancer in non-B cells upon overexpression of the basic helix-loop-helix (bHLH) protein E2A appears to be mediated not only by the binding of E2A to its cognate E box but also by the resulting displacement of a repressor from that same site. We have identified a "two-handed" zinc finger protein, denoted ZEB, the DNA-binding specificity of which mimics that of the cellular repressor. By employing a derivative E box that binds ZEB but not E2A, we have shown that the repressor is active in B cells and the IgH enhancer is silenced in the absence of binding competition by bHLH proteins. Hence, we propose that a necessary prerequisite of enhancer activity is the B-cell-specific displacement of a ZEB-like repressor by bHLH proteins.

Displacement of an E-box-binding repressor by basic helix-loop-helix proteins: implications for B-cell specificity of the immunoglobulin heavy-chain enhancer

1994 ◽  
Vol 14 (9) ◽  
pp. 6153-6163
Author(s):  
T Genetta ◽  
D Ruezinsky ◽  
T Kadesch
Keyword(s):  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Zinc Finger Protein ◽  
Immunoglobulin Heavy Chain ◽  
Bhlh Protein ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
Bhlh Proteins

The activity of the immunoglobulin heavy-chain (IgH) enhancer is restricted to B cells, although it binds both B-cell-restricted and ubiquitous transcription factors. Activation of the enhancer in non-B cells upon overexpression of the basic helix-loop-helix (bHLH) protein E2A appears to be mediated not only by the binding of E2A to its cognate E box but also by the resulting displacement of a repressor from that same site. We have identified a "two-handed" zinc finger protein, denoted ZEB, the DNA-binding specificity of which mimics that of the cellular repressor. By employing a derivative E box that binds ZEB but not E2A, we have shown that the repressor is active in B cells and the IgH enhancer is silenced in the absence of binding competition by bHLH proteins. Hence, we propose that a necessary prerequisite of enhancer activity is the B-cell-specific displacement of a ZEB-like repressor by bHLH proteins.

Dimerization through the helix-loop-helix motif enhances phosphorylation of the transcription activation domains of myogenin

1994 ◽  
Vol 14 (9) ◽  
pp. 6232-6243
Author(s):  
J Zhou ◽  
E N Olson
Keyword(s):  
Transcriptional Activity ◽  
Transcription Activation ◽  
Bhlh Protein ◽  
Specific Gene ◽  
Phosphorylation Sites ◽  
Gene Products ◽  
Activation Domains ◽  
Helix Loop Helix ◽  
Carboxyl Terminal ◽  
Bhlh Proteins

The muscle-specific basic helix-loop-helix (bHLH) protein myogenin activates muscle transcription by binding to target sequences in muscle-specific promoters and enhancers as a heterodimer with ubiquitous bHLH proteins, such as the E2A gene products E12 and E47. We show that dimerization with E2A products potentiates phosphorylation of myogenin at sites within its amino- and carboxyl-terminal transcription activation domains. Phosphorylation of myogenin at these sites was mediated by the bHLH region of E2A products and was dependent on dimerization but not on DNA binding. Mutations of the dimerization-dependent phosphorylation sites resulted in enhanced transcriptional activity of myogenin, suggesting that their phosphorylation diminishes myogenin's transcriptional activity. The ability of E2A products to potentiate myogenin phosphorylation suggests that dimerization induces a conformational change in myogenin that unmasks otherwise cryptic phosphorylation sites or that E2A proteins recruit a kinase for which myogenin is a substrate. That phosphorylation of these dimerization-dependent sites diminished myogenin's transcriptional activity suggests that these sites are targets for a kinase that interferes with muscle-specific gene expression.

Scleraxis: a basic helix-loop-helix protein that prefigures skeletal formation during mouse embryogenesis

Development ◽  
1995 ◽  
Vol 121 (4) ◽  
pp. 1099-1110 ◽  
Author(s):  
P. Cserjesi ◽  
D. Brown ◽  
K.L. Ligon ◽  
G.E. Lyons ◽  
N.G. Copeland ◽  
...  
Keyword(s):  
Connective Tissue ◽  
Expression Pattern ◽  
Consensus Sequence ◽  
Cell Types ◽  
Cell Type ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
Cell Type Specific ◽  
Bhlh Proteins

Members of the basic helix-loop-helix (bHLH) family of transcription factors have been shown to regulate growth and differentiation of numerous cell types. Cell-type-specific bHLH proteins typically form heterodimers with ubiquitous bHLH proteins, such as E12, and bind a DNA consensus sequence known as an E-box. We used the yeast two-hybrid system to screen mouse embryo cDNA libraries for cDNAs encoding novel cell-type-specific bHLH proteins that dimerize with E12. One of the cDNAs isolated encoded a novel bHLH protein, called scleraxis. During mouse embryogenesis, scleraxis transcripts were first detected between day 9.5 and 10.5 post coitum (p.c.) in the sclerotome of the somites and in mesenchymal cells in the body wall and limb buds. Subsequently, scleraxis was expressed at high levels within mesenchymal precursors of the axial and appendicular skeleton and in cranial mesenchyme in advance of chondrogenesis; its expression pattern in these cell types foreshadowed the developing skeleton. Prior to formation of the embryonic cartilaginous skeleton, scleraxis expression declined to low levels. As development proceeded, high levels of scleraxis expression became restricted to regions where cartilage and connective tissue formation take place. Scleraxis bound the E-box consensus sequence as a heterodimer with E12 and activated transcription of a reporter gene linked to its DNA-binding site. The expression pattern, DNA-binding properties and transcriptional activity of scleraxis suggest that it is a regulator of gene expression within mesenchymal cell lineages that give rise to cartilage and connective tissue.

scholarly journals Dimerization through the helix-loop-helix motif enhances phosphorylation of the transcription activation domains of myogenin.

1994 ◽  
Vol 14 (9) ◽  
pp. 6232-6243 ◽  
Author(s):  
J Zhou ◽  
E N Olson
Keyword(s):  
Transcriptional Activity ◽  
Transcription Activation ◽  
Bhlh Protein ◽  
Specific Gene ◽  
Phosphorylation Sites ◽  
Gene Products ◽  
Activation Domains ◽  
Helix Loop Helix ◽  
Carboxyl Terminal ◽  
Bhlh Proteins

The muscle-specific basic helix-loop-helix (bHLH) protein myogenin activates muscle transcription by binding to target sequences in muscle-specific promoters and enhancers as a heterodimer with ubiquitous bHLH proteins, such as the E2A gene products E12 and E47. We show that dimerization with E2A products potentiates phosphorylation of myogenin at sites within its amino- and carboxyl-terminal transcription activation domains. Phosphorylation of myogenin at these sites was mediated by the bHLH region of E2A products and was dependent on dimerization but not on DNA binding. Mutations of the dimerization-dependent phosphorylation sites resulted in enhanced transcriptional activity of myogenin, suggesting that their phosphorylation diminishes myogenin's transcriptional activity. The ability of E2A products to potentiate myogenin phosphorylation suggests that dimerization induces a conformational change in myogenin that unmasks otherwise cryptic phosphorylation sites or that E2A proteins recruit a kinase for which myogenin is a substrate. That phosphorylation of these dimerization-dependent sites diminished myogenin's transcriptional activity suggests that these sites are targets for a kinase that interferes with muscle-specific gene expression.

scholarly journals Identification of a new family of tissue-specific basic helix-loop-helix proteins with a two-hybrid system.

1995 ◽  
Vol 15 (7) ◽  
pp. 3813-3822 ◽  
Author(s):  
S M Hollenberg ◽  
R Sternglanz ◽  
P F Cheng ◽  
H Weintraub
Keyword(s):  
Bhlh Protein ◽  
Pharyngeal Arches ◽  
Tissue Specific ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
New Family ◽  
Specific Distribution ◽  
Nih 3T3 ◽  
Two Hybrid

With modified two-hybrid technology, we have isolated a member of a new family of basic helix-loop-helix (bHLH) transcription factors. Thing1 (Th1) was identified in a screen of a mouse embryo cDNA library as a partner for the Drosophila E protein daughterless. RNA in situ hybridization and reverse transcriptase-PCR demonstrate a stage- and tissue-specific distribution for the expression of Th1. Although tissue specific, the expression pattern of Th1 is fairly complex. During development, Th1 mRNA is widely expressed in extraembryonic tissues, portions of the heart, autonomic ganglia, the gut, and pharyngeal arches. At embryonic day 7.5 (E7.5), extraembryonic derivatives show robust Th1 expression. By E8.5, expression in the embryonic heart becomes detectable. During the next 2 days of development, the signal also includes gut and pharyngeal arches. Predominant expression at E13.5 is in neural crest derivatives, especially the autonomic nervous system and adrenal medulla. Expression of Th1 persists in the adult, in which it is localized to the smooth muscle cells of the gut. In vitro, Th1 protein recognizes a set of DNA sites that are more degenerate than has been determined for other bHLH factors, indicating a reduced binding specificity. Transient transfection of NIH 3T3 cells with GAL4-Th1 fusions reveals a repression activity mediated by the Th1 bHLH domain. In combination, these properties define Th1 as a new bHLH protein with a unique set of properties.

scholarly journals Intramolecular Regulation of MyoD Activation Domain Conformation and Function

1998 ◽  
Vol 18 (9) ◽  
pp. 5478-5484 ◽  
Author(s):  
Jing Huang ◽  
Hal Weintraub ◽  
Larry Kedes
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Activation Domain ◽  
Transcriptional Activation Domain ◽  
Helix Loop Helix ◽  
Dna Binding Specificity ◽  
E Box ◽  
And Function ◽  
Bhlh Proteins ◽  
Basic Region

ABSTRACT The MyoD family of basic helix-loop-helix (bHLH) proteins is required for myogenic determination and differentiation. The basic region carries the myogenic code and DNA binding specificity, while the N terminus contains a potent transcriptional activation domain. Myogenic activation is abolished when the basic region, bound to a myogenic E box, carries a mutation of Ala-114. It has been proposed that DNA binding of the MyoD basic region leads to recruitment of a recognition factor that unmasks the activation domain. Here we demonstrate that an A114N mutant exhibits an altered conformation in the basic region and that this local conformational difference can lead to a more global change affecting the conformation of the activation domain. This suggests that the deleterious effects of this class of mutations may result directly from defective conformation. Thus, the activation domain is unmasked only upon DNA binding by the correct basic region. Such a coupled conformational relationship may have evolved to restrict myogenic specificity to a small number of bHLH proteins among many with diverse functions yet with DNA binding specificities known to be similar.

scholarly journals Role of Basic-Helix-Loop-Helix Transcription Factors in Sertoli Cell Differentiation: Identification of an E-Box Response Element in the Transferrin Promoter*

Endocrinology ◽  
1997 ◽  
Vol 138 (2) ◽  
pp. 667-675 ◽  
Author(s):  
Jaideep Chaudhary ◽  
Andrea S. Cupp ◽  
Michael K. Skinner
Keyword(s):  
Transcription Factors ◽  
Cell Differentiation ◽  
Sertoli Cell ◽  
Sertoli Cells ◽  
Helix Loop Helix ◽  
Nuclear Extracts ◽  
E Box ◽  
Bhlh Factors ◽  
Gel Shift ◽  
Bhlh Proteins

Abstract Sertoli cells are critical for testicular function and maintenance of the spermatogenic process. The induction of Sertoli cell differentiation in the embryo promotes testicular development and male sex determination. The progression of Sertoli cell differentiation during puberty promotes the onset of spermatogenesis. The maintenance of optimal Sertoli cell differentiation in the adult is required for spermatogenesis to proceed. The current study was designed to investigate the transcriptional regulation of Sertoli cell differentiation through the analysis of a previously identified marker of differentiation, transferrin gene expression. Sertoli cells produce transferrin to transport iron to developing spermatogenic cells sequestered within the blood-testis barrier. The transferrin promoter was characterized and found to contain two critical response elements, designated Sertoli element 1 (SE1) and Sertoli element 2 (SE2). Through sequence analysis, SE2 was found to contain an E-box response element, which has been shown to respond to basic-helix-loop-helix (bHLH) transcription factors. The bHLH proteins are a class of transcription factors associated with the induction and progression of cell differentiation. bHLH proteins dimerize through the conserved helix-loop-helix region and bind DNA through the basic region. Nuclear extracts from Sertoli cells were found to cause an E-box gel shift when the cells were stimulated to differentiate in culture, but not under basal conditions. The SE2 gel shift of Sertoli nuclear extracts was competed with excess unlabeled SE2 or E-box DNA fragments. Several Sertoli nuclear proteins associate with the SE2 gel shifts, including 70-, 42-, and 25-kDa proteins. Therefore, the critical SE2 element in the transferrin promoter is an E-box element capable of binding bHLH transcription factors. The ubiquitously expressed E12 bHLH protein dimerizes with numerous cell-specific bHLH factors. A Western blot analysis demonstrated that E12 was present in Sertoli cell nuclear extracts and associated with the SE2 gel shift. A ligand blot of Sertoli cell nuclear extracts with radiolabeled E12 had apparent bHLH proteins when the cells were stimulated to differentiate. The E-box sequence in the SE2 fragment of the transferrin promoter was CATCTG and was similar in gel shifts to the consensus E-box elements (CANNTG) previously characterized. A bHLH inhibitory factor (Id) competed and inhibited formation of the Sertoli cell nuclear extract E-box gel shift. To extend this observation, Id protein was overexpressed in cultured Sertoli cells. A transferrin promoter chloramphenicol acetyltransferase construct was used to monitor Sertoli cell function. The presence of Id suppressed the activation of the promoter induced by Sertoli differentiation factors. Therefore, the inhibition of Sertoli bHLH factors by Id suppressed Sertoli cell differentiated function, as measured by transferrin expression. An E-box-chloramphenicol acetyltransferase construct was also found to be active in Sertoli cells when cells were induced to differentiate. Screening the computerized nucleotide data bases demonstrated that putative E-box response elements are present in the promoters of a large number of Sertoli cell differentiated genes. In summary, a critical E-box response element has been identified in the transferrin promoter that can be activated by bHLH factors (e.g. E12) present in Sertoli cells. Inhibition of Sertoli bHLH factors by Id suppresses Sertoli cell differentiated function (i.e. transferrin expression), suggesting that bHLH transcription factors may be important in regulating Sertoli cell differentiated functions.

scholarly journals SclR, a Basic Helix-Loop-Helix Transcription Factor, Regulates Hyphal Morphology and Promotes Sclerotial Formation in Aspergillus oryzae

2011 ◽  
Vol 10 (7) ◽  
pp. 945-955 ◽  
Author(s):  
Feng Jie Jin ◽  
Tadashi Takahashi ◽  
Ken-ichiro Matsushima ◽  
Seiichi Hara ◽  
Yasutomo Shinohara ◽  
...  
Keyword(s):  
Aspergillus Oryzae ◽  
Cell Function ◽  
Egfp Expression ◽  
Bhlh Protein ◽  
Protein Fusion ◽  
Content Type ◽  
Helix Loop Helix ◽  
Hyphal Morphology ◽  
Bhlh Proteins ◽  
Overexpressing Strain

ABSTRACT Most known basic-region helix-loop-helix (bHLH) proteins belong to a superfamily of transcription factors often involved in the control of growth and differentiation. Therefore, inappropriate expression of genes encoding bHLH proteins is frequently associated with developmental dysfunction. In our previously reported study, a novel bHLH protein-encoding gene (AO090011000215) of Aspergillus oryzae was identified. The gene-disrupted strain was found to produce dense conidia, but sparse sclerotia, relative to the parent strain. Here, to further analyze its function, we generated an overexpressing strain using the A. oryzae amyB gene promoter. Genetic overexpression led to a large number of initial hyphal aggregations and then the formation of mature sclerotia; it was therefore designated sclR ( scl erotium r egulator). At the same time, the sclR -overexpressing strain also displayed both delayed and decreased conidiation. Scanning electron microscopy indicated that the aerial hyphae of the sclR -overexpressing strain were extremely branched and intertwined with each other. In the generation of the SclR-enhanced green fluorescent protein (EGFP) expression strain, the SclR-EGFP protein fusion was conditionally detected in the nuclei. In addition, the loss of sclR function led to rapid protein degradation and cell lysis in dextrin-polypeptone-yeast extract liquid medium. Taken together, these observations indicate that SclR plays an important role in hyphal morphology, asexual conidiospore formation, and the promotion of sclerotial production, even retaining normal cell function, at least in submerged liquid culture.

scholarly journals Basic Helix-Loop-Helix Proteins Bind to TrkB and p21Cip1 Promoters Linking Differentiation and Cell Cycle Arrest in Neuroblastoma Cells

2004 ◽  
Vol 24 (7) ◽  
pp. 2662-2672 ◽  
Author(s):  
Yuhui Liu ◽  
Mario Encinas ◽  
Joan X. Comella ◽  
Martí Aldea ◽  
Carme Gallego
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Neuronal Differentiation ◽  
Ectopic Expression ◽  
Neurotrophin Receptor ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Cycle Arrest ◽  
E Box ◽  
Bhlh Proteins

ABSTRACT Differentiation of precursor into specialized cells involves an increasing restriction in proliferative capacity, culminating in cell cycle exit. In this report we used a human neuroblastoma cell line to study the molecular mechanisms that coordinate cell cycle arrest and neuronal differentiation. Exposure to retinoic acid (RA), a differentiation agent in many cell types, causes an upregulation of neurotrophin receptor TrkB and the cyclin kinase inhibitor p21Cip1 at a transcriptional level. Full transcriptional activation of these two genes requires canonical E-box sequences found in the TrkB and p21Cip1 promoters. As reported for other E-box-regulated promoters, ectopic expression of E47 and E12 basic helix-loop-helix (bHLH) proteins enhances RA-dependent expression of TrkB and p21Cip1 , whereas the inhibitory HLH Id2 exerts opposite effects. In addition, ectopic expression of E47 and NeuroD, a neuronal bHLH protein, is able to activate TrkB transcription in the absence of RA. More importantly, we show that E47 and NeuroD proteins bind the TrkB and p21Cip1 promoter sequences in vivo. Since they establish a direct transcriptional link between a cell cycle inhibitor, p21Cip1 , and a neurotrophic receptor, TrkB, bHLH proteins would play an important role in coordinating key events of cell cycle arrest and neuronal differentiation.

Sign in / Sign up

Export Citation Format

Share Document