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 The Homeodomain of PDX-1 Mediates Multiple Protein-Protein Interactions in the Formation of a Transcriptional Activation Complex on the Insulin Promoter

2000 ◽  
Vol 20 (3) ◽  
pp. 900-911 ◽  
Author(s):  
Kinuko Ohneda ◽  
Raghavendra G. Mirmira ◽  
Juehu Wang ◽  
Jeffrey D. Johnson ◽  
Michael S. German
Keyword(s):  
Gene Transcription ◽  
Transcriptional Activation ◽  
Insulin Gene ◽  
Nuclear Proteins ◽  
Bhlh Protein ◽  
Homeodomain Protein ◽  
Β Cells ◽  
Activation Domains ◽  
Insulin Promoter ◽  
Insulin Gene Transcription

ABSTRACT Activation of insulin gene transcription specifically in the pancreatic β cells depends on multiple nuclear proteins that interact with each other and with sequences on the insulin gene promoter to build a transcriptional activation complex. The homeodomain protein PDX-1 exemplifies such interactions by binding to the A3/4 region of the rat insulin I promoter and activating insulin gene transcription by cooperating with the basic-helix-loop-helix (bHLH) protein E47/Pan1, which binds to the adjacent E2 site. The present study provides evidence that the homeodomain of PDX-1 acts as a protein-protein interaction domain to recruit multiple proteins, including E47/Pan1, BETA2/NeuroD1, and high-mobility group protein I(Y), to an activation complex on the E2A3/4 minienhancer. The transcriptional activity of this complex results from the clustering of multiple activation domains capable of interacting with coactivators and the basal transcriptional machinery. These interactions are not common to all homeodomain proteins: the LIM homeodomain protein Lmx1.1 can also activate the E2A3/4 minienhancer in cooperation with E47/Pan1 but does so through different interactions. Cooperation between Lmx1.1 and E47/Pan1 results not only in the aggregation of multiple activation domains but also in the unmasking of a potent activation domain on E47/Pan1 that is normally silent in non-β cells. While more than one activation complex may be capable of activating insulin gene transcription through the E2A3/4 minienhancer, each is dependent on multiple specific interactions among a unique set of nuclear proteins.

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.

scholarly journals Induction of c-Myc Expression Suppresses Insulin Gene Transcription by Inhibiting NeuroD/BETA2-mediated Transcriptional Activation

2002 ◽  
Vol 277 (15) ◽  
pp. 12998-13006 ◽  
Author(s):  
Hideaki Kaneto ◽  
Arun Sharma ◽  
Kiyoshi Suzuma ◽  
D. Ross Laybutt ◽  
Gang Xu ◽  
...  
Keyword(s):  
Gene Transcription ◽  
Transcriptional Activation ◽  
Insulin Gene ◽  
Insulin Gene Transcription

scholarly journals Insulin Gene Transcription Is Mediated by Interactions between the p300 Coactivator and PDX-1, BETA2, and E47

2002 ◽  
Vol 22 (2) ◽  
pp. 412-420 ◽  
Author(s):  
Yi Qiu ◽  
Min Guo ◽  
Suming Huang ◽  
Roland Stein
Keyword(s):  
Dna Binding ◽  
Rna Polymerase Ii ◽  
Gene Transcription ◽  
Present Report ◽  
Amino Acid Sequences ◽  
Insulin Gene ◽  
Homeodomain Protein ◽  
Β Cells ◽  
Β Cell ◽  
Insulin Gene Transcription

ABSTRACT Pancreatic β-cell-type-specific expression of the insulin gene requires both ubiquitous and cell-enriched activators, which are organized within the enhancer region into a network of protein-protein and protein-DNA interactions to promote transcriptional synergy. Protein-protein-mediated communication between DNA-bound activators and the RNA polymerase II transcriptional machinery is inhibited by the adenovirus E1A protein as a result of E1A’s binding to the p300 coactivator. E1A disrupts signaling between the non-DNA-binding p300 protein and the basic helix-loop-helix DNA-binding factors of insulin’s E-element activator (i.e., the islet-enriched BETA2 and generally distributed E47 proteins), as well as a distinct but unidentified enhancer factor. In the present report, we show that E1A binding to p300 prevents activation by insulin’s β-cell-enriched PDX-1 activator. p300 interacts directly with the N-terminal region of the PDX-1 homeodomain protein, which contains conserved amino acid sequences essential for activation. The unique combination of PDX-1, BETA2, E47, and p300 was shown to promote synergistic activation from a transfected insulin enhancer-driven reporter construct in non-β cells, a process inhibited by E1A. In addition, E1A inhibited the level of PDX-1 and BETA2 complex formation in β cells. These results indicate that E1A inhibits insulin gene transcription by preventing communication between the p300 coactivator and key DNA-bound activators, like PDX-1 and BETA2:E47.

scholarly journals XIHbox 8, an endoderm-specific Xenopus homeodomain protein, is closely related to a mammalian insulin gene transcription factor.

1994 ◽  
Vol 8 (6) ◽  
pp. 806-816
Author(s):  
M Peshavaria ◽  
L Gamer ◽  
E Henderson ◽  
G Teitelman ◽  
C V Wright ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Gene Transcription ◽  
Insulin Gene ◽  
Homeodomain Protein ◽  
Insulin Gene Transcription

scholarly journals Analysis of the Role of E2A-Encoded Proteins in Insulin Gene Transcription

1997 ◽  
Vol 11 (11) ◽  
pp. 1608-1617 ◽  
Author(s):  
Arun Sharma ◽  
Eva Henderson ◽  
Laura Gamer ◽  
Yuan Zhuang ◽  
Roland Stein
Keyword(s):  
Gene Transcription ◽  
Present Report ◽  
Insulin Gene ◽  
Apparent Difference ◽  
Transactivation Domain ◽  
Β Cell ◽  
Helix Loop Helix ◽  
Encoded Proteins ◽  
Gene Enhancer ◽  
Insulin Gene Transcription

Abstract Pancreatic β-cell type-specific transcription of the insulin gene is mediated, in part, by factors in the basic helix-loop-helix (bHLH) family that act on a site within the insulin enhancer, termed the E1-box. Expression from this element is regulated by a heteromeric protein complex containing ubiquitous (i.e. the E2A- and HEB-encoded proteins) and islet-enriched members of the bHLH family. Recent studies indicate that the E2A- and HEB-encoded proteins contain a transactivation domain, termed AD2, that functions more efficiently in transfected β-cell lines. In the present report, we extend this observation by demonstrating that expression of full-length E2A proteins (E47, E12, and E2/5) activates insulin E element-directed transcription in a β-cell line-selective manner. Stimulation required functional interactions with other key insulin gene transcription factors, including its islet bHLH partner as well as those that act on the RIPE3b1 and RIPE3a2 elements of the insulin gene enhancer. The conserved AD2 domain in the E2A proteins was essential in this process. The effect of the E2A- and HEB-encoded proteins on insulin gene expression was also analyzed in mice lacking a functional E2A or HEB gene. There was no apparent difference in insulin production between wild type, heterozygote, and homozygous mutant E2A or HEB mice. These results suggest that neither the E2A- or HEB-encoded proteins are essential for insulin transcription and that one factor can substitute for the other to impart normal insulin E1 activator function in mutant animals.

Analysis of ∼700 Human Tissue Samples Identifies microRNAs That Are Associated with, Predictive of, and Necessary for Insulin Gene Transcription

Diabetes ◽  
2018 ◽  
Vol 67 (Supplement 1) ◽  
pp. 2160-P
Author(s):  
ANAND HARDIKAR ◽  
WILSON WONG ◽  
MUGDHA JOGLEKAR ◽  
LOUISE T. DALGAARD ◽  
ALICIA JENKINS ◽  
...  
Keyword(s):  
Gene Transcription ◽  
Human Tissue ◽  
Insulin Gene ◽  
Tissue Samples ◽  
Insulin Gene Transcription

scholarly journals The Islet β Cell-enriched MafA Activator Is a Key Regulator of Insulin Gene Transcription

2005 ◽  
Vol 280 (12) ◽  
pp. 11887-11894 ◽  
Author(s):  
Li Zhao ◽  
Min Guo ◽  
Taka-aki Matsuoka ◽  
Derek K. Hagman ◽  
Susan D. Parazzoli ◽  
...  
Keyword(s):  
Gene Transcription ◽  
Insulin Gene ◽  
Β Cell ◽  
Insulin Gene Transcription
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