scholarly journals Relative contribution of PDX-1, MafA and E47/β2 to the regulation of the human insulin promoter

2005 ◽  
Vol 389 (3) ◽  
pp. 813-820 ◽  
Author(s):  
Hilary M. Docherty ◽  
Colin W. Hay ◽  
Laura A. Ferguson ◽  
John Barrow ◽  
Elaine Durward ◽  
...  
Keyword(s):  
Human Insulin ◽  
Promoter Activity ◽  
Leucine Zipper ◽  
Synergistic Effects ◽  
Regulatory Elements ◽  
Basic Leucine Zipper ◽  
Helix Loop Helix ◽  
Relative Contribution ◽  
Endogenous Insulin ◽  
Insulin Promoter

The insulin promoter binds a number of tissue-specific and ubiquitous transcription factors. Of these, the homoeodomain protein PDX-1 (pancreatic duodenal homeobox factor-1), the basic leucine zipper protein MafA and the basic helix–loop–helix heterodimer E47/BETA2 (β-cell E box transactivator 2; referred to here as β2) bind to important regulatory sites. Previous studies have shown that PDX-1 can interact synergistically with E47 and β2 to activate the rat insulin 1 promoter. The aim of the present study was to determine the relative contribution of PDX-1, MafA and E47/β2 in regulating the human insulin promoter, and whether these factors could interact synergistically in the context of the human promoter. Mutagenesis of the PDX-1, MafA and E47/β2 binding sites reduced promoter activity by 60, 74 and 94% respectively, in INS-1 β-cells. In the islet glucagonoma cell line αTC1.6, overexpression of PDX-1 and MafA separately increased promoter activity approx. 2.5–3-fold, and in combination approx. 6-fold, indicating that their overall effect was additive. Overexpression of E47 and β2 had no effect. In HeLa cells, PDX-1 stimulated the basal promoter by approx. 40-fold, whereas MafA, E47 and β2 each increased activity by less than 2-fold. There was no indication of any synergistic effects on the human insulin promoter. On the other hand, the rat insulin 1 promoter and a mutated version of the human insulin promoter, in which the relevant regulatory elements were separated by the same distances as in the rat insulin 1 promoter, did exhibit synergy. PDX-1 was shown further to activate the endogenous insulin 1 gene in αTC1.6 cells, whereas MafA activated the insulin 2 gene. In combination, PDX-1 and MafA activated both insulin genes. Chromatin immunoprecipitation assays confirmed that PDX-1 increased the association of acetylated histones H3 and H4 with the insulin 1 gene and MafA increased the association of acetylated histone H3 with the insulin 2 gene.

scholarly journals ATF2 Interacts with β-Cell-enriched Transcription Factors, MafA, Pdx1, and Beta2, and Activates Insulin Gene Transcription

2011 ◽  
Vol 286 (12) ◽  
pp. 10449-10456 ◽  
Author(s):  
Song-iee Han ◽  
Kunio Yasuda ◽  
Kohsuke Kataoka
Keyword(s):  
Transcription Factors ◽  
Leucine Zipper ◽  
Binding Capacity ◽  
Immunohistochemical Analysis ◽  
Regulatory Elements ◽  
Insulin Gene ◽  
Β Cell ◽  
Mobility Shift ◽  
Basic Leucine Zipper ◽  
Insulin Promoter

Pancreatic β-cell-restricted expression of insulin is established through several critical cis-regulatory elements located in the insulin gene promoter region. The principal cis elements are A-boxes, E1, and C1/RIPE3b. The β-cell-enriched transcription factors Pdx1 and Beta2 bind to the A-boxes and E1 element, respectively. A β-cell-specific trans-acting factor binding to C1/RIPE3b (termed RIPE3b1 activator) was detected by electrophoretic mobility shift assay and has been identified as MafA, a member of the Maf family of basic leucine zipper (bZip) proteins. Here, ATF2, a member of the ATF/CREB family of basic leucine zipper proteins, was identified as a component of the RIPE3b1 activator. ATF2 alone was unable to bind to the C1/RIPE3b element but acquired binding capacity upon complex formation with MafA. ATF2 also interacted with Pdx1 and Beta2, and co-expression of ATF2, MafA, Pdx1, and Beta2 resulted in a synergistic activation of the insulin promoter. Immunohistochemical analysis of mouse pancreas tissue sections showed that ATF2 is enriched in islet endocrine cells, including β-cells. RNAi-mediated knockdown of MafA or ATF2 in the MIN6 β-cell line resulted in a significant decrease in endogenous levels of insulin mRNA. These data indicate that ATF2 is an essential component of the positive regulators of the insulin gene expression.

scholarly journals Regulation of Nitrate (NO3) Transporters and Glutamate Synthase-Encoding Genes under Drought Stress in Arabidopsis: The Regulatory Role of AtbZIP62 Transcription Factor

Plants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2149
Author(s):  
Nkulu Kabange Rolly ◽  
Byung-Wook Yun
Keyword(s):  
Transcription Factor ◽  
Drought Stress ◽  
Leucine Zipper ◽  
Target Genes ◽  
De Novo ◽  
In Silico Analysis ◽  
Glutamate Synthase ◽  
Regulatory Elements ◽  
Transcript Accumulation ◽  
Basic Leucine Zipper

Nitrogen (N) is an essential macronutrient, which contributes substantially to the growth and development of plants. In the soil, nitrate (NO3) is the predominant form of N available to the plant and its acquisition by the plant involves several NO3 transporters; however, the mechanism underlying their involvement in the adaptive response under abiotic stress is poorly understood. Initially, we performed an in silico analysis to identify potential binding sites for the basic leucine zipper 62 transcription factor (AtbZIP62 TF) in the promoter of the target genes, and constructed their protein–protein interaction networks. Rather than AtbZIP62, results revealed the presence of cis-regulatory elements specific to two other bZIP TFs, AtbZIP18 and 69. A recent report showed that AtbZIP62 TF negatively regulated AtbZIP18 and AtbZIP69. Therefore, we investigated the transcriptional regulation of AtNPF6.2/NRT1.4 (low-affinity NO3 transporter), AtNPF6.3/NRT1.1 (dual-affinity NO3 transporter), AtNRT2.1 and AtNRT2.2 (high-affinity NO3 transporters), and AtGLU1 and AtGLU2 (both encoding glutamate synthase) in response to drought stress in Col-0. From the perspective of exploring the transcriptional interplay of the target genes with AtbZIP62 TF, we measured their expression by qPCR in the atbzip62 (lacking the AtbZIP62 gene) under the same conditions. Our recent study revealed that AtbZIP62 TF positively regulates the expression of AtPYD1 (Pyrimidine 1, a key gene of the de novo pyrimidine biosynthesis pathway know to share a common substrate with the N metabolic pathway). For this reason, we included the atpyd1-2 mutant in the study. Our findings revealed that the expression of AtNPF6.2/NRT1.4, AtNPF6.3/NRT1.1 and AtNRT2.2 was similarly regulated in atzbip62 and atpyd1-2 but differentially regulated between the mutant lines and Col-0. Meanwhile, the expression pattern of AtNRT2.1 in atbzip62 was similar to that observed in Col-0 but was suppressed in atpyd1-2. The breakthrough is that AtNRT2.2 had the highest expression level in Col-0, while being suppressed in atbzip62 and atpyd1-2. Furthermore, the transcript accumulation of AtGLU1 and AtGLU2 showed differential regulation patterns between Col-0 and atbzip62, and atpyd1-2. Therefore, results suggest that of all tested NO3 transporters, AtNRT2.2 is thought to play a preponderant role in contributing to NO3 transport events under the regulatory influence of AtbZIP62 TF in response to drought stress.

scholarly journals Repression of IL-2 Promoter Activity by the Novel Basic Leucine Zipper p21SNFTProtein

2000 ◽  
Vol 165 (2) ◽  
pp. 860-868 ◽  
Author(s):  
Milena Iacobelli ◽  
William Wachsman ◽  
Kathleen L. McGuire
Keyword(s):  
Promoter Activity ◽  
Leucine Zipper ◽  
The Novel ◽  
Basic Leucine Zipper

scholarly journals Phenothiazine Neuroleptics Signal to the Human Insulin Promoter as Revealed by a Novel High-Throughput Screen

2010 ◽  
Vol 15 (6) ◽  
pp. 663-670 ◽  
Author(s):  
Alice Kiselyuk ◽  
Suzette Farber-Katz ◽  
Tom Cohen ◽  
Seung-Hee Lee ◽  
Ifat Geron ◽  
...  
Keyword(s):  
Cell Line ◽  
Human Insulin ◽  
High Throughput ◽  
High Throughput Screening ◽  
Promoter Activity ◽  
Central Element ◽  
Bhlh Transcription Factor ◽  
Β Cell ◽  
Insulin Promoter ◽  
Short Term Exposure

A number of diabetogenic stimuli interact to influence insulin promoter activity, making it an attractive target for both mechanistic studies and therapeutic interventions. High-throughput screening (HTS) for insulin promoter modulators has the potential to reveal novel inputs into the control of that central element of the pancreatic β-cell. A cell line from human islets in which the expression of insulin and other β-cell-restricted genes are modulated by an inducible form of the bHLH transcription factor E47 was developed. This cell line, T6PNE, was adapted for HTS by transduction with a vector expressing green fluorescent protein under the control of the human insulin promoter. The resulting cell line was screened against a library of known drugs for those that increase insulin promoter activity. Members of the phenothiazine class of neuroleptics increased insulin gene expression upon short-term exposure. Chronic treatment, however, resulted in suppression of insulin promoter activity, consistent with the effect of phenothiazines observed clinically to induce diabetes in chronically treated patients. In addition to providing insights into previously unrecognized targets and mechanisms of action of phenothiazines, the novel cell line described here provides a broadly applicable platform for mining new molecular drug targets and central regulators of β-cell differentiated function.

CRITERIA FOR AN UPDATED CLASSIFICATION OF HUMAN TRANSCRIPTION FACTOR DNA-BINDING DOMAINS

2013 ◽  
Vol 11 (01) ◽  
pp. 1340007 ◽  
Author(s):  
EDGAR WINGENDER
Keyword(s):  
Dna Binding ◽  
Leucine Zipper ◽  
Regulatory Elements ◽  
Biological Species ◽  
Basic Leucine Zipper ◽  
Dna Binding Domains ◽  
Binding Domains ◽  
Comprehensive Classification ◽  
Human Transcription Factor

By binding to cis-regulatory elements in a sequence-specific manner, transcription factors regulate the activity of nearby genes. Here, we discuss the criteria for a comprehensive classification of human TFs based on their DNA-binding domains. In particular, classification of basic leucine zipper (bZIP) and zinc finger factors is exemplarily discussed. The resulting classification can be used as a template for TFs of other biological species.

scholarly journals Mad1 Function Is Regulated through Elements within the Carboxy Terminus

2000 ◽  
Vol 20 (12) ◽  
pp. 4253-4264 ◽  
Author(s):  
Gonzalo Barrera-Hernandez ◽  
Constance M. Cultraro ◽  
Stefania Pianetti ◽  
Shoshana Segal
Keyword(s):  
Amino Acids ◽  
Transcriptional Activation ◽  
Transcriptional Repression ◽  
Leucine Zipper ◽  
Regulatory Elements ◽  
Carboxy Terminus ◽  
Helix Loop Helix ◽  
Inhibitory Function ◽  
Growth Inhibitory ◽  
Differentiation Block

ABSTRACT Myc and Mad are basic helix-loop-helix leucine zipper (bHLH-LZ) proteins that heterodimerize with Max to bind DNA and thereby influence the transcription of Myc-responsive genes. Myc-Max dimers transactivate whereas Mad-Max-mSin3 complexes repress Myc-mediated transcriptional activation. We have previously shown that the N-terminal mSin3 binding domain and the centrally located bHLH-LZ are required for Mad1 to function during a molecular switch from proliferation to differentiation. Here we demonstrate that the carboxy terminus (CT) of Mad1 contains previously unidentified motifs necessary for the regulation of Mad1 function. We show that removal of the last 18 amino acids of Mad1 (region V) abolishes the growth-inhibitory function of the protein and the ability to reverse a Myc-imposed differentiation block. Moreover, deletion of region V results in a protein that binds DNA weakly and no longer represses Myc-dependent transcriptional activation. In contrast, deletion of the preceding 24 amino acids (region IV) together with region V restores DNA binding and transcriptional repression, suggesting a functional interplay between these two regions. Furthermore, phosphorylation within region IV appears to mediate this interplay. These findings indicate that novel regulatory elements are present in the Mad1 CT.

scholarly journals c-Jun represses the human insulin promoter activity that depends on multiple cAMP response elements.

1992 ◽  
Vol 89 (3) ◽  
pp. 1045-1049 ◽  
Author(s):  
N. Inagaki ◽  
T. Maekawa ◽  
T. Sudo ◽  
S. Ishii ◽  
Y. Seino ◽  
...  
Keyword(s):  
Human Insulin ◽  
Promoter Activity ◽  
Response Elements ◽  
Insulin Promoter
Sign in / Sign up

Export Citation Format

Share Document