scholarly journals Orphan Nuclear Receptor Small Heterodimer Partner, a Novel Corepressor for a Basic Helix-Loop-Helix Transcription Factor BETA2/NeuroD

2004 ◽  
Vol 18 (4) ◽  
pp. 776-790 ◽  
Author(s):  
Joon-Young Kim ◽  
Khoi Chu ◽  
Han-Jong Kim ◽  
Hyun-A Seong ◽  
Ki-Cheol Park ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Nuclear Receptor ◽  
Transcriptional Activity ◽  
Orphan Nuclear Receptor ◽  
Small Heterodimer Partner ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box ◽  
Coactivator P300

Abstract Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor that lacks a conventional DNA binding domain (DBD) and represses the transcriptional activity of various nuclear receptors. In this study, we examined the novel cross talk between SHP and BETA2/NeuroD, a basic helix-loop-helix transcription factor. In vitro and in vivo protein interaction studies showed that SHP physically interacts with BETA2/NeuroD, but not its heterodimer partner E47. Moreover, confocal microscopic study and immunostaining results demonstrated that SHP colocalized with BETA2 in islets of mouse pancreas. SHP inhibited BETA2/NeuroD-dependent transactivation of an E-box reporter, whereas SHP was unable to repress the E47-mediated transactivation and the E-box mutant reporter activity. In addition, SHP repressed the BETA2-dependent activity of glucokinase and cyclin-dependent kinase inhibitor p21 gene promoters. Gel shift and in vitro protein competition assays indicated that SHP inhibits neither dimerization nor DNA binding of BETA2 and E47. Rather, SHP directly repressed BETA2 transcriptional activity and p300-enhanced BETA2/NeuroD transcriptional activity by inhibiting interaction between BETA2 and coactivator p300. We also showed that C-terminal repression domain within SHP is also required for BETA2 repression. However, inhibition of BETA2 activity was not observed by naturally occurring human SHP mutants that cannot interact with BETA2/NeuroD. Taken together, these results suggest that SHP acts as a novel corepressor for basic helix-loop-helix transcription factor BETA2/NeuroD by competing with coactivator p300 for binding to BETA2/NeuroD and by its direct transcriptional repression function.

scholarly journals Targeting the Microphthalmia Basic Helix-Loop-Helix–Leucine Zipper Transcription Factor to a Subset of E-Box Elements In Vitro and In Vivo

1998 ◽  
Vol 18 (12) ◽  
pp. 6930-6938 ◽  
Author(s):  
I. Aksan ◽  
C. R. Goding
Keyword(s):  
Transcription Factor ◽  
Leucine Zipper ◽  
Pigment Cells ◽  
Specific Gene ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
P Gene ◽  
E Box

ABSTRACT The development of melanocytes, which are pigment-producing cells responsible for skin, hair, and eye color, is absolutely dependent on the action of the microphthalmia basic helix-loop-helix–leucine zipper (bHLH-LZ) transcription factor (Mi); mice lacking a functional Mi protein are entirely devoid of pigment cells. Mi has been shown to activate transcription of the tyrosinase,TRP-1, TRP-2, and QNR-71 genes through specific E-box elements, most notably the highly conserved M box. We investigated the mechanism which enables Mi to be recruited specifically to a restricted subset of E boxes in target promoters while being prevented from binding E-box elements in other promoters. We show both in vitro and in vivo that the presence of a T residue flanking a CATGTG E box is an essential determinant of the ability of Mi to bind DNA, and we successfully predict that the CATGTG E box from the P gene would not bind Mi. In contrast, no specific requirement for the sequences flanking a CACGTG E box was observed, and no binding to an atypical E box in the c-Kit promoter was detected. The relevance of these observations to the control of melanocyte-specific gene expression was highlighted by the fact that the E-box elements located in thetyrosinase, TRP-1, TRP-2, andQNR-71 promoters without exception possess a 5′ flanking T residue which is entirely conserved between species as diverse as man and turtle. The ability of Mi to discriminate between different E-box motifs provides a mechanism to restrict the repertoire of genes which are likely to be regulated by Mi and provides insight into the ability of bHLH-LZ transcription factors to achieve the specificity required for the precise coordination of transcription during development.

scholarly journals β-Catenin Interacts with MyoD and Regulates Its Transcription Activity

2008 ◽  
Vol 28 (9) ◽  
pp. 2941-2951 ◽  
Author(s):  
Chang-Hoon Kim ◽  
Hannah Neiswender ◽  
Eun Joo Baik ◽  
Wen C. Xiong ◽  
Lin Mei
Keyword(s):  
Transcription Factor ◽  
Transcriptional Activity ◽  
Muscle Development ◽  
Muscle Cells ◽  
Muscle Differentiation ◽  
Canonical Pathway ◽  
Transcription Activity ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
E Box

ABSTRACT Wnt regulation of muscle development is thought to be mediated by the β-catenin-TCF/LEF-dependent canonical pathway. Here we demonstrate that β-catenin, not TCF/LEF, is required for muscle differentiation. We showed that β-catenin interacts directly with MyoD, a basic helix-loop-helix transcription factor essential for muscle differentiation and enhances its binding to E box elements and transcriptional activity. MyoD-mediated transactivation is inhibited in muscle cells when β-catenin is deficient or the interaction between MyoD and β-catenin is disrupted. These results demonstrate that β-catenin is necessary for MyoD function, identifying MyoD as an effector in the Wnt canonical pathway.

Sclerotome-related helix-loop-helix type transcription factor (scleraxis) mRNA is expressed in osteoblasts and its level is enhanced by type-β transforming growth factor

1996 ◽  
Vol 151 (3) ◽  
pp. 491-499 ◽  
Author(s):  
Y Liu ◽  
P Cserjesi ◽  
A Nifuji ◽  
E N Olson ◽  
M Noda
Keyword(s):  
Transcription Factor ◽  
Growth Factor ◽  
Transcriptional Activity ◽  
Transforming Growth Factor ◽  
Binding Activity ◽  
The Novel ◽  
Helix Loop Helix ◽  
Nuclear Extracts ◽  
E Box ◽  
First Time

Abstract Scleraxis is a recently identified transcription factor with a basic helix-loop-helix motif, which is expressed in sclerotome during embryonic development. We have examined the expression of scleraxis mRNA in rat osteoblastic cells and found that the scleraxis gene was expressed as a 1·2 kb mRNA species in osteoblastic osteosarcoma ROS 17/2·8 cells. The scleraxis mRNA expression was enhanced by type-β transforming growth factor (TGFβ) treatment. The TGFβ effect was observed in a dosedependent manner starting at 0·2 ng/ml and saturating at 2 ng/ml. The effect was time-dependent and was first observed within 12 h and peaked at 24 h. The TGFβ effect was blocked by cycloheximide, while no effect on scleraxis mRNA stability was observed. TGFβ treatment enhanced scleraxis-E box (Scx-E) binding activity in the nuclear extracts of ROS17/2·8 cells. Furthermore, TGFβ enhanced transcriptional activity of the CAT constructs which contain the Scx-E box sequence. TGFβ treatment also enhanced scleraxis gene expression in osteoblastenriched cells derived from primary rat calvaria. These findings indicated for the first time that the novel helixloop-helix type transcription factor (scleraxis) mRNA is expressed in osteoblasts and its expression is regulated by TGFβ. Journal of Endocrinology (1996) 151, 491–499

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.

scholarly journals Id1 Overexpression Induces Tetraploidization and Multiple Abnormal Mitotic Phenotypes by Modulating Aurora A

2008 ◽  
Vol 19 (6) ◽  
pp. 2389-2401 ◽  
Author(s):  
Cornelia Man ◽  
Jack Rosa ◽  
Y. L. Yip ◽  
Annie Lai-Man Cheung ◽  
Y. L. Kwong ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Epithelial Cells ◽  
Transcriptional Activity ◽  
Dna Amplification ◽  
Centrosome Amplification ◽  
Aurora A ◽  
Cell Models ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Binding Partners

The basic helix-loop-helix transcription factor, Id1, was shown to induce tetraploidy in telomerase-immortalized nasopharyngeal epithelial cells in this study. Using both transient and stable Id1-expressing cell models, multiple mitotic aberrations were detected, including centrosome amplification, binucleation, spindle defects, and microtubule perturbation. Many of these abnormal phenotypes have previously been reported in cells overexpressing Aurora A. Further experiments showed that Id1 could stabilize Aurora A, whereas knocking down Aurora A expression in Id1-expressing cells could rescue some of the mitotic defects. The mechanisms by which Aurora A could be modulated by Id1 were explored. DNA amplification of the Aurora A locus was not involved. Id1 could only weakly activate the transcriptional activity of the Aurora A promoter. We found that Id1 overexpression could affect Aurora A degradation, leading to its stabilization. Aurora A is normally degraded from mitosis exit by the APC/CCdh1-mediated proteasomal proteolysis pathway. Our results revealed that Id1 and Cdh1 are binding partners. The association of Id1 and Cdh1 was found to be dependent on the canonical destruction box motif of Id1, the increased binding of which may compete with the interaction between Cdh1 and Aurora A, leading to stabilization of Aurora A in Id1-overexpressing cells.

scholarly journals Bile acids inhibit duodenal secretin expression via orphan nuclear receptor small heterodimer partner (SHP)

2009 ◽  
Vol 297 (1) ◽  
pp. G90-G97 ◽  
Author(s):  
Ian P. Y. Lam ◽  
Leo T. O. Lee ◽  
Hueng-Sik Choi ◽  
Gianfranco Alpini ◽  
Billy K. C. Chow
Keyword(s):  
Gene Expression ◽  
Bile Acids ◽  
Nuclear Receptor ◽  
Target Genes ◽  
In Vivo Studies ◽  
Control Group ◽  
Orphan Nuclear Receptor ◽  
Small Heterodimer Partner

Small heterodimer partner (SHP) is an orphan nuclear receptor in which gene expression can be upregulated by bile acids. It regulates its target genes by repressing the transcriptional activities of other nuclear receptors including NeuroD, which has been shown to regulate secretin gene expression. Here, we evaluated the regulation on duodenal secretin gene expression by SHP and selected bile acids, cholic acid (CA) and chenodeoxycholic acid (CDCA). In vitro treatment of CDCA or fexaramine elevated the SHP transcript level and occupancy on secretin promoter. The increase in the SHP level, induced by bile acid treatment or overexpression, reduced secretin gene expression, whereas this gene inhibitory effect was reversed by silencing of endogenous SHP. In in vivo studies, double-immunofluorescence staining demonstrated the coexpression of secretin and SHP in mouse duodenum. Feeding mice with 1% CA-enriched rodent chow resulted in upregulation of SHP and a concomitant decrease in secretin transcript and protein levels in duodenum compared with the control group fed with normal chow. A diet enriched with 5% cholestyramine led to a decrease in SHP level and a corresponding increase in secretin expression. Overall, this study showed that bile acids via SHP inhibit duodenal secretin gene expression. Because secretin is a key hormone that stimulates bile flow in cholangiocytes, this pathway thus provides a novel means to modulate secretin-stimulated choleresis in response to intraduodenal bile acids.

scholarly journals p300 Mediates Transcriptional Stimulation by the Basic Helix-Loop-Helix Activators of the Insulin Gene

1998 ◽  
Vol 18 (5) ◽  
pp. 2957-2964 ◽  
Author(s):  
Yi Qiu ◽  
Arun Sharma ◽  
Roland Stein
Keyword(s):  
Amino Acids ◽  
Adenovirus Type ◽  
Insulin Gene ◽  
Β Cells ◽  
Β Cell ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Endogenous Insulin ◽  
E Box

ABSTRACT Pancreatic β-cell-type-specific and glucose-inducible transcription of the insulin gene is mediated by the basic helix-loop-helix factors that bind to and activate expression from an E-box element within its enhancer. The E-box activator is a heteromeric complex composed of a β-cell-enriched factor, BETA2/NeuroD, and ubiquitously distributed proteins encoded by the E2A and HEB genes. Previously, we demonstrated that the adenovirus type 5 E1A proteins repressed stimulation by the E-box activator in β cells. In this study, our objective was to determine how E1A repressed activator function. The results indicate that E1A reduces activation by binding to and sequestering the p300 cellular coactivator protein. Thus, we show that expression of p300 in β cells can relieve inhibition by E1A, as well as potentiate activation by the endogenous insulin E-box transcription factors. p300 stimulated activation from GAL4 (amino acids 1 to 147) fusion constructs of either BETA2/NeuroD or the E2A-encoded E47 protein. The sequences spanning the activation domains of BETA2/NeuroD (amino acids 156 to 355) and E47 (amino acids 1 to 99 and 325 to 432) were required for this response. The same region of BETA2/NeuroD was shown to be important for binding to p300 in vitro. The sequences of p300 involved in E47 and BETA2/NeuroD association resided between amino acids 1 and 1257 and 1945 and 2377, respectively. A mutation in p300 that abolished binding to BETA2/NeuroD also destroyed the ability of p300 to activate insulin E-box-directed transcription in β cells. Our results indicate that physical and functional interactions between p300 and the E-box activator factors play an important role in insulin gene transcription.

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