scholarly journals Two distinct class A helix-loop-helix transcription factors, E2A and BETA1, form separate DNA binding complexes on the insulin gene E box.

1994 ◽  
Vol 269 (41) ◽  
pp. 25936-25941
Author(s):  
M Peyton ◽  
L G Moss ◽  
M J Tsai
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Insulin Gene ◽  
Distinct Class ◽  
Class A ◽  
Helix Loop Helix ◽  
E Box ◽  
Dna Binding Complexes

scholarly journals Cell-specific helix-loop-helix factor required for pituitary expression of the pro-opiomelanocortin gene.

1993 ◽  
Vol 13 (4) ◽  
pp. 2342-2353 ◽  
Author(s):  
M Therrien ◽  
J Drouin
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Binding Proteins ◽  
Specific Activity ◽  
Pituitary Cells ◽  
Immunoglobulin Gene ◽  
Helix Loop Helix ◽  
E Box ◽  
E Boxes ◽  
Hlh Transcription Factors

Pro-opiomelanocortin (POMC)-expressing cells appear to be the first pituitary cells committed to hormone production. In this work, we have identified an element of the POMC promoter which confers cell-specific activity. This element did not exhibit any activity on its own and required at least one other element of the promoter to manifest its cell-specific activity. Fine mutagenesis of this element indicated that a CANNTG motif is responsible for activity. This E-box motif is typical of binding sites for helix-loop-helix (HLH) transcription factors; however, the POMC cell-specific E box cannot be replaced by other E boxes like the kappa E2 site of the immunoglobulin gene or a muscle-specific E box. Similar E boxes which are present in the insulin gene promoter were shown to contribute to the pancreatic specificity of the insulin promoter. However, E-box-binding proteins found in nuclear extracts from POMC-expressing AtT-20 cells and from insulin-expressing cells have different electrophoretic mobilities. The AtT-20 proteins were named CUTE (for corticotroph upstream transcription element-binding) proteins, and they were not found in any other cells. CUTE proteins have DNA-binding properties characteristic of HLH transcription factors. Overexpression of the dominant negative HLH protein Id or of the ubiquitous positive HLH factor rat Pan-2 decreased or augmented POMC promoter activity, respectively. These observations are consistent with the hypothesis that CUTE factors might be heterodimers. This hypothesis was further supported by antibody shift experiments and by abrogation of DNA binding in the presence of bacterially expressed Id protein. Thus, the cell-specific CUTE proteins and their binding site in the POMC promoter appear to be important determinants for cell specificity of this promoter. The requirement for HLH factors in POMC transcription also presents the possibility that these factors are involved in differentiation of pituitary cells, in analogy with the role of HLH factors in muscle development.

scholarly journals Cell-specific helix-loop-helix factor required for pituitary expression of the pro-opiomelanocortin gene

1993 ◽  
Vol 13 (4) ◽  
pp. 2342-2353
Author(s):  
M Therrien ◽  
J Drouin
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Binding Proteins ◽  
Specific Activity ◽  
Pituitary Cells ◽  
Immunoglobulin Gene ◽  
Helix Loop Helix ◽  
E Box ◽  
E Boxes ◽  
Hlh Transcription Factors

Pro-opiomelanocortin (POMC)-expressing cells appear to be the first pituitary cells committed to hormone production. In this work, we have identified an element of the POMC promoter which confers cell-specific activity. This element did not exhibit any activity on its own and required at least one other element of the promoter to manifest its cell-specific activity. Fine mutagenesis of this element indicated that a CANNTG motif is responsible for activity. This E-box motif is typical of binding sites for helix-loop-helix (HLH) transcription factors; however, the POMC cell-specific E box cannot be replaced by other E boxes like the kappa E2 site of the immunoglobulin gene or a muscle-specific E box. Similar E boxes which are present in the insulin gene promoter were shown to contribute to the pancreatic specificity of the insulin promoter. However, E-box-binding proteins found in nuclear extracts from POMC-expressing AtT-20 cells and from insulin-expressing cells have different electrophoretic mobilities. The AtT-20 proteins were named CUTE (for corticotroph upstream transcription element-binding) proteins, and they were not found in any other cells. CUTE proteins have DNA-binding properties characteristic of HLH transcription factors. Overexpression of the dominant negative HLH protein Id or of the ubiquitous positive HLH factor rat Pan-2 decreased or augmented POMC promoter activity, respectively. These observations are consistent with the hypothesis that CUTE factors might be heterodimers. This hypothesis was further supported by antibody shift experiments and by abrogation of DNA binding in the presence of bacterially expressed Id protein. Thus, the cell-specific CUTE proteins and their binding site in the POMC promoter appear to be important determinants for cell specificity of this promoter. The requirement for HLH factors in POMC transcription also presents the possibility that these factors are involved in differentiation of pituitary cells, in analogy with the role of HLH factors in muscle development.

scholarly journals Helix-loop-helix transcription factors mediate activation and repression of the p75LNGFR gene.

1995 ◽  
Vol 15 (11) ◽  
pp. 6036-6044 ◽  
Author(s):  
A Chiaramello ◽  
K Neuman ◽  
K Palm ◽  
M Metsis ◽  
T Neuman
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Transcription Factors ◽  
Promoter Activity ◽  
Stable Complex ◽  
Dual Function ◽  
Class A ◽  
Helix Loop Helix ◽  
E Box ◽  
Bhlh Transcription Factors

Sequence analysis of rat and human low-affinity nerve growth factor receptor p75LNGFR gene promoter regions revealed a single E-box cis-acting element, located upstream of the major transcription start sites. Deletion analysis of the E-box sequence demonstrated that it significantly contributes to p75LNGFR promoter activity. This E box has a dual function; it mediates either activation or repression of the p75LNGFR promoter activity, depending on the interacting transcription factors. We showed that the two isoforms of the class A basic helix-loop-helix (bHLH) transcription factor ME1 (ME1a and ME1b), the murine homolog of the human HEB transcription factor, specifically repress p75LNGFR promoter activity. This repression can be released by coexpression of the HLH Id2 transcriptional regulator. In vitro analyses demonstrated that ME1a forms a stable complex with the p75LNGFR E box and likely competes with activating E-box-binding proteins. By using ME1a-overexpressing PC12 cells, we showed that the endogenous p75LNGFR gene is a target of ME1a repression. Together, these data demonstrate that the p75LNGFR E box and the interacting bHLH transcription factors are involved in the regulation of p75LNGFR gene expression. These results also show that class A bHLH transcription factors can repress and Id-like negative regulators can stimulate gene expression.

scholarly journals Preferred sequences for DNA recognition by the TAL1 helix-loop-helix proteins.

1994 ◽  
Vol 14 (2) ◽  
pp. 1256-1265 ◽  
Author(s):  
H L Hsu ◽  
L Huang ◽  
J T Tsan ◽  
W Funk ◽  
W E Wright ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Dna Binding ◽  
Lymphoblastic Leukemia ◽  
Dna Recognition ◽  
Binding Activity ◽  
Class A ◽  
Helix Loop Helix ◽  
Dna Binding Activity ◽  
Cell Acute Lymphoblastic Leukemia

Tumor-specific activation of the TAL1 gene is the most common genetic alteration seen in patients with T-cell acute lymphoblastic leukemia. The TAL1 gene products contain the basic helix-loop-helix (bHLH) domain, a protein dimerization and DNA-binding motif common to several known transcription factors. A binding-site selection procedure has now been used to evaluate the DNA recognition properties of TAL1. These studies demonstrate that TAL1 polypeptides do not have intrinsic DNA-binding activity, presumably because of their inability to form bHLH homodimers. However, TAL1 readily interacts with any of the known class A bHLH proteins (E12, E47, E2-2, and HEB) to form heterodimers that bind DNA in a sequence-specific manner. The TAL1 heterodimers preferentially recognize a subset of E-box elements (CANNTG) that can be represented by the consensus sequence AACAGATGGT. This consensus is composed of half-sites for recognition by the participating class A bHLH polypeptide (AACAG) and the TAL1 polypeptide (ATGGT). TAL1 heterodimers with DNA-binding activity are readily detected in nuclear extracts of Jurkat, a leukemic cell line derived from a patient with T-cell acute lymphoblastic leukemia. Hence, TAL1 is likely to bind and regulate the transcription of a unique subset of subordinate target genes, some of which may mediate the malignant function of TAL1 during T-cell leukemogenesis.

scholarly journals The Proneural Proteins Atonal and Scute Regulate Neural Target Genes through Different E-Box Binding Sites

2004 ◽  
Vol 24 (21) ◽  
pp. 9517-9526 ◽  
Author(s):  
Lynn M. Powell ◽  
Petra I. zur Lage ◽  
David R. A. Prentice ◽  
Biruntha Senthinathan ◽  
Andrew P. Jarman
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Binding Sites ◽  
Tandem Repeats ◽  
Target Genes ◽  
Expression Patterns ◽  
Sense Organ ◽  
Ample Evidence ◽  
E Box ◽  
Bhlh Transcription Factors

ABSTRACT For a particular functional family of basic helix-loop-helix (bHLH) transcription factors, there is ample evidence that different factors regulate different target genes but little idea of how these different target genes are distinguished. We investigated the contribution of DNA binding site differences to the specificities of two functionally related proneural bHLH transcription factors required for the genesis of Drosophila sense organ precursors (Atonal and Scute). We show that the proneural target gene, Bearded, is regulated by both Scute and Atonal via distinct E-box consensus binding sites. By comparing with other Ato-dependent enhancer sequences, we define an Ato-specific binding consensus that differs from the previously defined Scute-specific E-box consensus, thereby defining distinct EAto and ESc sites. These E-box variants are crucial for function. First, tandem repeats of 20-bp sequences containing EAto and ESc sites are sufficient to confer Atonal- and Scute-specific expression patterns, respectively, on a reporter gene in vivo. Second, interchanging EAto and ESc sites within enhancers almost abolishes enhancer activity. While the latter finding shows that enhancer context is also important in defining how proneural proteins interact with these sites, it is clear that differential utilization of DNA binding sites underlies proneural protein specificity.

scholarly journals Characterization of the bHLH Family of Transcriptional Regulators in the ACOELS. roscoffensisand their Putative Role in Neurogenesis

2017 ◽  
Author(s):  
E Perea-Atienza ◽  
S.G. Sprecher ◽  
P Martínez
Keyword(s):  
Gene Expression ◽  
Nervous System ◽  
Transcription Factors ◽  
Expression Patterns ◽  
Developmental Expression ◽  
Class A ◽  
Helix Loop Helix ◽  
Specific Subset ◽  
Bhlh Genes ◽  
Eukaryotic Organisms

ABSTRACTBackgroundThe basic Helix loop helix (bHLH) family of transcription factors is one of the largest superfamilies of regulatory transcription factors and are widely used in eukaryotic organisms. They play an essential role in a range of metabolic, physiological, and developmental processes, including the development of the nervous system (NS). These transcription factors have been studied in many metazoans, especially in vertebrates but also in early branching metazoan clades such as the cnidarians and sponges. However, currently very little is known about their expression in the most basally branching bilaterian group, the xenacoelomorphs. Recently, our laboratory has characterized the full complement of bHLH in the genome of two members of the Xenacoelomorpha, the xenoturbellidXenoturbella bockiand the acoelSymsagittifera roscoffensis. Understanding the patterns of bHLH gene expression in members of this phylum (in space and time) provides critical new insights into the conserved roles of the bHLH and their putative specificities in this group. Our focus is on deciphering the specific roles that these genes have in the process of neurogenesis.ResultsHere, we analyze the developmental expression of the whole complement of bHLH genes identified in the acoelS. roscoffensis.Based on their expression patterns several members of bHLH class A appear to have specific conserved roles in neurogenesis, while other class A genes (as well as members of other classes) have likely taken on more generalized functions. All gene expression patterns are described in embryos and early juveniles.ConclusionOur results suggest that the main roles of the bHLH genes ofS. roscoffensisare evolutionarily conserved, with a specific subset dedicated to patterning the nervous system: SrAscA, SrAscB, SrHes/Hey, SrNscl, SrSrebp, SrE12/E47 and SrOlig.

Murine helix-loop-helix transcriptional activator proteins binding to the E-box motif of the Akv murine leukemia virus enhancer identified by cDNA cloning

1992 ◽  
Vol 12 (8) ◽  
pp. 3449-3459
Author(s):  
A L Nielsen ◽  
N Pallisgaard ◽  
F S Pedersen ◽  
P Jørgensen
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Transcriptional Activator ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
Nih 3T3 ◽  
Murine Leukemia

The enhancer region of Akv murine leukemia virus contains the sequence motif ACAGATGG. This sequence is homologous to the E-box motif originally defined as a regulatory element in the enhancers of immunoglobulin mu and kappa genes. We have used double-stranded oligonucleotide probes, corresponding to the E box of the murine leukemia virus Akv, to screen a randomly primed lambda gt11 cDNA expression library made from mouse NIH 3T3 fibroblast RNA. We have identified seven lambda clones expressing DNA-binding proteins representing two different genes termed ALF1 and ALF2. The results of sequencing ALF2 cDNA suggests that we have recovered the gene for the basic-helix-loop-helix transcription factor A1, the murine analog of the human transcription factor E47. The cDNA sequence of ALF1 codes for a new member of the basic-helix-loop-helix protein family. Two splice variants of ALF1 cDNA have been found, differing by a 72-bp insertion, coding for putative proteins of 682 and 706 amino acids. The two ALF1 mRNAs are expressed at various levels in mouse tissues. In vitro DNA binding assays, using prokaryotically expressed ALF1 proteins, demonstrated specific binding of the ALF1 proteins to the Akv murine leukemia virus E-box motif ACAGATGG. Expression in NIH 3T3 fibroblasts of GAL4-ALF1 chimeric protein stimulated expression from a minimal promoter linked to a GAL4 binding site, indicating the existence of a transcriptional activator domain in ALF1.

Preferred sequences for DNA recognition by the TAL1 helix-loop-helix proteins

1994 ◽  
Vol 14 (2) ◽  
pp. 1256-1265
Author(s):  
H L Hsu ◽  
L Huang ◽  
J T Tsan ◽  
W Funk ◽  
W E Wright ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Dna Binding ◽  
Lymphoblastic Leukemia ◽  
Dna Recognition ◽  
Binding Activity ◽  
Class A ◽  
Helix Loop Helix ◽  
Dna Binding Activity ◽  
Cell Acute Lymphoblastic Leukemia

Tumor-specific activation of the TAL1 gene is the most common genetic alteration seen in patients with T-cell acute lymphoblastic leukemia. The TAL1 gene products contain the basic helix-loop-helix (bHLH) domain, a protein dimerization and DNA-binding motif common to several known transcription factors. A binding-site selection procedure has now been used to evaluate the DNA recognition properties of TAL1. These studies demonstrate that TAL1 polypeptides do not have intrinsic DNA-binding activity, presumably because of their inability to form bHLH homodimers. However, TAL1 readily interacts with any of the known class A bHLH proteins (E12, E47, E2-2, and HEB) to form heterodimers that bind DNA in a sequence-specific manner. The TAL1 heterodimers preferentially recognize a subset of E-box elements (CANNTG) that can be represented by the consensus sequence AACAGATGGT. This consensus is composed of half-sites for recognition by the participating class A bHLH polypeptide (AACAG) and the TAL1 polypeptide (ATGGT). TAL1 heterodimers with DNA-binding activity are readily detected in nuclear extracts of Jurkat, a leukemic cell line derived from a patient with T-cell acute lymphoblastic leukemia. Hence, TAL1 is likely to bind and regulate the transcription of a unique subset of subordinate target genes, some of which may mediate the malignant function of TAL1 during T-cell leukemogenesis.

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.

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