scholarly journals c-jun inhibits insulin control element-mediated transcription by affecting the transactivation potential of the E2A gene products.

1995 ◽  
Vol 15 (3) ◽  
pp. 1398-1404 ◽  
Author(s):  
G L Robinson ◽  
E Henderson ◽  
M E Massari ◽  
C Murre ◽  
R Stein
Keyword(s):  
Amino Acids ◽  
Beta Cells ◽  
Pancreatic Beta Cell ◽  
Insulin Gene ◽  
Control Element ◽  
Transactivation Domain ◽  
Pancreatic Islet Cell ◽  
Transactivation Potential ◽  
Insulin Control

Pancreatic beta-cell-type-specific transcription of the insulin gene is principally controlled by trans-acting factors which influence insulin control element (ICE)-mediated expression. The ICE activator is composed, in part, of the basic helix-loop-helix proteins E12, E47, and E2-5 encoded by the E2A gene. Previous experiments showed that ICE activation in beta cells was repressed in vivo by the c-jun proto-oncogene (E. Henderson and R. Stein, Mol. Cell. Biol. 14:655-662, 1994). Here we focus on the mechanism by which c-Jun inhibits ICE-mediated activation. c-Jun was shown to specifically repress the transactivation potential of the E2A proteins. Thus, we found that the activity of GAL4:E2A fusion constructs was inhibited by c-Jun. The transrepression capabilities of c-Jun were detected only in pancreatic islet cell lines that contained a functional ICE activator. Repression of GAL4:E2A was mediated by the basic leucine zipper regions of c-Jun, which are also the essential regions of this protein necessary for controlling ICE activator-stimulated expression in vivo. The specific target of c-Jun repression was the transactivation domain (located between amino acids 345 and 408 in E12 and E47) conserved in E12, E47, and E2-5. In contrast, the activation domain unique to the E12 and E47 proteins (located between amino acids 1 and 99) was unresponsive to c-Jun. Our results indicate that c-Jun inhibits insulin gene transcription in beta cells by reducing the transactivation potential of the E2A proteins present in the ICE activator complex.

scholarly journals Isolation and characterization of a novel transcription factor that binds to and activates insulin control element-mediated expression.

1994 ◽  
Vol 14 (10) ◽  
pp. 6704-6714 ◽  
Author(s):  
G L Robinson ◽  
S R Cordle ◽  
E Henderson ◽  
P A Weil ◽  
G Teitelman ◽  
...  
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Insulin Gene ◽  
Negative Regulator ◽  
Bhlh Protein ◽  
Control Element ◽  
Sequence Element ◽  
Isolation And Characterization ◽  
Insulin Control

Pancreatic beta-cell-type-specific transcription of the insulin gene is principally regulated by a single cis-acting DNA sequence element, termed the insulin control element (ICE), which is found within the 5'-flanking region of the gene. The ICE activator is a heteromeric complex composed of an islet alpha/beta-cell-specific factor associated with the ubiquitously distributed E2A-encoded proteins (E12, E47, and E2-5). We describe the isolation and characterization of a cDNA for a protein present in alpha and beta cells, termed INSAF for insulin activator factor, which binds to and activates ICE-mediated expression. INSAF was isolated from a human insulinoma cDNA library. Transfection experiments demonstrated that INSAF activates ICE expression in insulin-expressing cells but not in non-insulin-expressing cells. Cotransfection experiments showed that activation by INSAF was inhibited by Id, a negative regulator of basic helix-loop-helix (bHLH) protein function. INSAF was also shown to associate in vitro with the bHLH protein E12. In addition, affinity-purified INSAF antiserum abolished the formation of the activator-specific ICE-binding complex. Immunohistochemical studies indicate that INSAF is restricted in terms of its expression pattern, in that INSAF appears to be detected only within the nuclei of islet pancreatic alpha and beta cells. All of these data are consistent with the proposal that INSAF is either part of the ICE activator or is antigenically related to the specific activator required for insulin gene transcription.

c-jun inhibits transcriptional activation by the insulin enhancer, and the insulin control element is the target of control

1994 ◽  
Vol 14 (1) ◽  
pp. 655-662
Author(s):  
E Henderson ◽  
R Stein
Keyword(s):  
Skeletal Muscle ◽  
Beta Cells ◽  
Gene Transcription ◽  
Transcriptional Activation ◽  
Pancreatic Beta Cells ◽  
Insulin Gene ◽  
Control Element ◽  
Basic Leucine Zipper ◽  
Insulin Control ◽  
Insulin Gene Transcription

Selective transcription of the insulin gene in pancreatic beta cells is regulated by its enhancer, located between nucleotides -340 and -91 relative to the transcription start site. One of the principal control elements within the enhancer is found between nucleotides -100 and -91 (GCCATCTGCT, referred to as the insulin control element [ICE]) and is regulated by both positive- and negative-acting transcription factors in the helix-loop-helix (HLH) family. It was previously shown that the c-jun proto-oncogene can repress insulin gene transcription. We have found that c-jun inhibits ICE-stimulated transcription. Inhibition of ICE-directed transcription is mediated by sequences within the carboxy-terminal region of the protein. These c-jun sequences span an activation domain and the basic leucine zipper DNA binding-dimerization region of the protein. Both regions of c-jun are conserved within the other members of the jun family: junB and junD. These proteins also suppress ICE-mediated transcription. The jun proteins do not appear to inhibit insulin gene transcription by binding directly to the ICE. c-jun and junB also block the trans-activation potential of two skeletal muscle-specific HLH proteins, MyoD and myogenin. These results suggests that the jun proteins may be common transcription control factors used in skeletal muscle and pancreatic beta cells to regulate HLH-mediated activity. We discuss the possible significance of these observations to insulin gene transcription in pancreatic beta cells.

scholarly journals c-jun inhibits transcriptional activation by the insulin enhancer, and the insulin control element is the target of control.

1994 ◽  
Vol 14 (1) ◽  
pp. 655-662 ◽  
Author(s):  
E Henderson ◽  
R Stein
Keyword(s):  
Skeletal Muscle ◽  
Beta Cells ◽  
Gene Transcription ◽  
Transcriptional Activation ◽  
Pancreatic Beta Cells ◽  
Insulin Gene ◽  
Control Element ◽  
Basic Leucine Zipper ◽  
Insulin Control ◽  
Insulin Gene Transcription

Selective transcription of the insulin gene in pancreatic beta cells is regulated by its enhancer, located between nucleotides -340 and -91 relative to the transcription start site. One of the principal control elements within the enhancer is found between nucleotides -100 and -91 (GCCATCTGCT, referred to as the insulin control element [ICE]) and is regulated by both positive- and negative-acting transcription factors in the helix-loop-helix (HLH) family. It was previously shown that the c-jun proto-oncogene can repress insulin gene transcription. We have found that c-jun inhibits ICE-stimulated transcription. Inhibition of ICE-directed transcription is mediated by sequences within the carboxy-terminal region of the protein. These c-jun sequences span an activation domain and the basic leucine zipper DNA binding-dimerization region of the protein. Both regions of c-jun are conserved within the other members of the jun family: junB and junD. These proteins also suppress ICE-mediated transcription. The jun proteins do not appear to inhibit insulin gene transcription by binding directly to the ICE. c-jun and junB also block the trans-activation potential of two skeletal muscle-specific HLH proteins, MyoD and myogenin. These results suggests that the jun proteins may be common transcription control factors used in skeletal muscle and pancreatic beta cells to regulate HLH-mediated activity. We discuss the possible significance of these observations to insulin gene transcription in pancreatic beta cells.

Isolation and characterization of a novel transcription factor that binds to and activates insulin control element-mediated expression

1994 ◽  
Vol 14 (10) ◽  
pp. 6704-6714
Author(s):  
G L Robinson ◽  
S R Cordle ◽  
E Henderson ◽  
P A Weil ◽  
G Teitelman ◽  
...  
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Insulin Gene ◽  
Negative Regulator ◽  
Bhlh Protein ◽  
Control Element ◽  
Sequence Element ◽  
Isolation And Characterization ◽  
Insulin Control

Pancreatic beta-cell-type-specific transcription of the insulin gene is principally regulated by a single cis-acting DNA sequence element, termed the insulin control element (ICE), which is found within the 5'-flanking region of the gene. The ICE activator is a heteromeric complex composed of an islet alpha/beta-cell-specific factor associated with the ubiquitously distributed E2A-encoded proteins (E12, E47, and E2-5). We describe the isolation and characterization of a cDNA for a protein present in alpha and beta cells, termed INSAF for insulin activator factor, which binds to and activates ICE-mediated expression. INSAF was isolated from a human insulinoma cDNA library. Transfection experiments demonstrated that INSAF activates ICE expression in insulin-expressing cells but not in non-insulin-expressing cells. Cotransfection experiments showed that activation by INSAF was inhibited by Id, a negative regulator of basic helix-loop-helix (bHLH) protein function. INSAF was also shown to associate in vitro with the bHLH protein E12. In addition, affinity-purified INSAF antiserum abolished the formation of the activator-specific ICE-binding complex. Immunohistochemical studies indicate that INSAF is restricted in terms of its expression pattern, in that INSAF appears to be detected only within the nuclei of islet pancreatic alpha and beta cells. All of these data are consistent with the proposal that INSAF is either part of the ICE activator or is antigenically related to the specific activator required for insulin gene transcription.

Glucose-induced transcription of the insulin gene is mediated by factors required for beta-cell-type-specific expression

1994 ◽  
Vol 14 (2) ◽  
pp. 871-879
Author(s):  
A Sharma ◽  
R Stein
Keyword(s):  
Beta Cell ◽  
Insulin Gene ◽  
Control Element ◽  
Cell Type ◽  
Specific Expression ◽  
Cis Acting ◽  
Cell Extracts ◽  
Cell Type Specific Expression ◽  
Cell Type Specific

The insulin gene is expressed exclusively in pancreatic islet beta cells. The principal regulator of insulin gene transcription in the islet is the concentration of circulating glucose. Previous studies have demonstrated that transcription is regulated by the binding of trans-acting factors to specific cis-acting sequences within the 5'-flanking region of the insulin gene. To identify the cis-acting control elements within the rat insulin II gene that are responsible for regulating glucose-stimulated expression in the beta cell, we analyzed the effect of glucose on the in vivo expression of a series of transfected 5'-flanking deletion mutant constructs. We demonstrate that glucose-induced transcription of the rat insulin II gene is mediated by sequences located between -126 and -91 bp relative to the transcription start site. This region contains two cis-acting elements that are essential for directing pancreatic beta-cell-type-specific expression of the rat insulin II gene, the insulin control element (ICE; -100 to -91 bp) and RIPE3b1 (-115 to -107 bp). The gel mobility shift assay was used to determine whether the formation of the ICE- and RIPE3b1-specific factor-DNA element complexes were affected in glucose-treated beta-cell extracts. We found that RIPE3b1 binding activity was selectively induced by about eightfold. In contrast, binding to other insulin cis-acting element sequences like the ICE and RIPE3a2 (-108 to -99 bp) were unaffected by these conditions. The RIPE3b1 binding complex was shown to be distinct from the glucose-inducible factor that binds to an element located between -227 to -206 bp of the human and rat insulin I genes (D. Melloul, Y. Ben-Neriah, and E. Cerasi, Proc. Natl. Acad. Sci. USA 90:3865-3869, 1993). We have also shown that mannose, a sugar that can be metabolized by the beta cell, mimics the effects of glucose in the in vivo transfection assays and the in vitro RIPE3b1 binding assays. These results suggested that the RIPE3b1 transcription factor is a primary regulator of glucose-mediated transcription of the insulin gene. However, we found that mutations in either the ICE or the RIPE3b1 element reduced glucose-responsive expression from transfected 5'-flanking rat insulin II gene constructs. We therefore conclude that glucose-regulated transcription of the insulin gene is mediated by cis-acting elements required for beta-cell-type-specific expression.

scholarly journals Glucagon-Like Peptide-1 Triggers Protective Pathways in Pancreatic Beta-Cells Exposed to Glycated Serum

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Alessandra Puddu ◽  
Roberta Sanguineti ◽  
Arianna Durante ◽  
Alessio Nencioni ◽  
François Mach ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Cell Function ◽  
Pancreatic Beta Cell ◽  
Redox Balance ◽  
Insulin Gene ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Pancreatic Beta Cell Function

Advanced glycation end products (AGEs) might play a pathophysiological role in the development of diabetes and its complications. AGEs negatively affect pancreatic beta-cell function and the expression of transcriptional factors regulating insulin gene. Glucagon-like peptide-1 (GLP-1), an incretin hormone that regulates glucose homeostasis, might counteract the harmful effects of AGEs on the beta cells in culture. The aim of this study was to identify the intracellular mechanisms underlying GLP-1-mediated protection from AGE-induced detrimental activities in pancreatic beta cells. HIT-T15 cells were cultured for 5 days with glycated serum (GS, consisting in a pool of AGEs), in the presence or absence of 10 nmol/L GLP-1. After evaluation of oxidative stress, we determined the expression and subcellular localization of proteins involved in maintaining redox balance and insulin gene expression, such as nuclear factor erythroid-derived 2 (Nrf2), glutathione reductase, PDX-1, and MafA. Then, we investigated proinsulin production. The results showed that GS increased oxidative stress, reduced protein expression of all investigated factors through proteasome activation, and decreased proinsulin content. Furthermore, GS reduced ability of PDX-1 and MafA to bind DNA. Coincubation with GLP-1 reversed these GS-mediated detrimental effects. In conclusion, GLP-1, protecting cells against oxidants, triggers protective intercellular pathways in HIT-T15 cells exposed to GS.

scholarly journals Functional characterization of the transactivation properties of the PDX-1 homeodomain protein.

1997 ◽  
Vol 17 (7) ◽  
pp. 3987-3996 ◽  
Author(s):  
M Peshavaria ◽  
E Henderson ◽  
A Sharma ◽  
C V Wright ◽  
R Stein
Keyword(s):  
Amino Acids ◽  
Gene Transcription ◽  
Transcriptional Activation ◽  
Functional Characterization ◽  
Insulin Gene ◽  
Regulatory Sequences ◽  
Homeodomain Protein ◽  
Transactivation Domain ◽  
Endogenous Insulin ◽  
Insulin Gene Transcription

Pancreas formation is prevented in mice carrying a null mutation in the PDX-1 homeoprotein, demonstrating a key role for this factor in development. PDX-1 can also bind to and activate transcription from cis-acting regulatory sequences in the insulin and somatostatin genes, which are expressed in pancreatic islet beta and delta cells, respectively. In this study, we compared the functional properties of PDX-1 with those of the closely related Xenopus homeoprotein XIHbox8. Analysis of chimeras between PDX-1, XIHbox8, and the DNA-binding domain of the Saccharomyces cerevisiae transcription factor GAL4 revealed that their transactivation domain was contained within the N-terminal region (amino acids 1 to 79). Detailed mutagenesis of this region indicated that transactivation is mediated by three highly conserved sequences, spanning amino acids 13 to 22 (subdomain A), 32 to 38 (subdomain B), and 60 to 73 (subdomain C). These sequences were also required by PDX-1 to synergistically activate insulin enhancer-mediated transcription with another key insulin gene activator, the E2A-encoded basic helix-loop-helix E2-5 and E47 proteins. These results indicated that N-terminal sequences conserved between the mammalian PDX-1 and Xenopus XIHbox8 proteins are important in transcriptional activation. Stable expression of the PDX-1 deltaABC mutant in the insulin- and PDX-1-expressing betaTC3 cell line resulted in a threefold reduction in the rate of endogenous insulin gene transcription. Strikingly, the level of the endogenous PDX-1 protein was reduced to very low levels in these cells. These results suggest that PDX-1 is not absolutely essential for insulin gene expression in betaTC3 cells. We discuss the possible significance of these findings for insulin gene transcription in islet beta cells.

scholarly journals Islet-specific Prmt5 excision leads to reduced insulin expression and glucose intolerance in mice

2020 ◽  
Vol 244 (1) ◽  
pp. 41-52
Author(s):  
Jian Ma ◽  
Xin He ◽  
Yan Cao ◽  
Kienan O’Dwyer ◽  
Katherine M Szigety ◽  
...  
Keyword(s):  
Glucose Tolerance ◽  
Mouse Model ◽  
Beta Cell ◽  
Impaired Glucose Tolerance ◽  
Beta Cells ◽  
Gene Transcription ◽  
Insulin Gene ◽  
Beta Cell Proliferation ◽  
Arginine Methyltransferase

Protein arginine methyltransferase 5 (PRMT5), a symmetric arginine methyltransferase, regulates cell functions by influencing gene transcription through posttranslational modification of histones and non-histone proteins. PRMT5 interacts with multiple partners including menin, which controls beta cell homeostasis. However, the role of Prmt5 in pancreatic islets, particularly in beta cells, remains unclear. A mouse model with an islet-specific knockout (KO) of the Prmt5 gene was generated, and the influence of the Prmt5 excision on beta cells was investigated via morphologic and functional studies. Beta cell function was evaluated by glucose tolerance test (GTT) and glucose-stimulated insulin secretion (GSIS) test. Beta cell proliferation was evaluated by immunostaining. Gene expression change was determined by real-time qPCR. Molecular mechanisms were investigated in beta cells in vitro and in vivo in Prmt5 KO mice. The results show that islet-specific KO of Prmt5 reduced expression of the insulin gene and impaired glucose tolerance and GSIS in vivo. The mechanistic study indicated that PRMT5 is involved in the regulation of insulin gene transcription, likely via histone methylation-related chromatin remodeling. The reduced expression of insulin in beta cells in the Prmt5 KO mice may contribute to impaired glucose tolerance (IGT) and deficient GSIS in the mouse model. These results will provide new insights into exploring novel strategies to treat diabetes caused by insulin insufficiency.

scholarly journals The role of the insulin control element and RIPE3b1 activators in glucose-stimulated transcription of the insulin gene.

1995 ◽  
Vol 9 (11) ◽  
pp. 1468-1476
Author(s):  
A Sharma ◽  
D Fusco-DeMane ◽  
E Henderson ◽  
S Efrat ◽  
R Stein
Keyword(s):  
Insulin Gene ◽  
Control Element ◽  
Insulin Control
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