scholarly journals Novel Transcriptional Potentiation of BETA2/NeuroD on the Secretin Gene Promoter by the DNA-Binding Protein Finb/RREB-1

2003 ◽  
Vol 23 (1) ◽  
pp. 259-271 ◽  
Author(s):  
Subir K. Ray ◽  
Junko Nishitani ◽  
Mary W. Petry ◽  
Michael Y. Fessing ◽  
Andrew B. Leiter
Keyword(s):  
Dna Binding ◽  
Zinc Finger Protein ◽  
Mutational Analysis ◽  
Gene Promoter ◽  
Expression Cloning ◽  
Physical Interaction ◽  
Activation Domain ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Distinct Category

ABSTRACT The basic helix-loop-helix protein BETA2/NeuroD activates transcription of the secretin gene and is essential for terminal differentiation of secretin-producing enteroendocrine cells. However, in heterodimeric complexes with its partner basic helix-loop-helix proteins, BETA2 does not appear to be a strong activator of transcription by itself. Mutational analysis of a proximal enhancer in the secretin gene identified several cis-acting elements in addition to the E-box binding site for BETA2. We identified by expression cloning the zinc finger protein RREB-1, also known to exist as a longer form, Finb, as the protein binding to one of the mutationally sensitive elements. Finb/RREB-1 lacks an intrinsic activation domain and by itself did not activate secretin gene transcription. Here we show that Finb/RREB-1 can associate with BETA2 to enhance its transcription-activating function. Both DNA binding and physical interaction of Finb/RREB-1 with BETA2 are required to potentiate transcription. Thus, Finb/RREB-1 does not function as a classical activator of transcription that recruits an activation domain to a DNA-protein complex. Finb/RREB-1 may be distinguished from coactivators, which increase transcription without sequence-specific DNA binding. We suggest that Finb/RREB-1 should be considered a potentiator of transcription, representing a distinct category of transcription-regulating proteins.

Identification of transactivation and repression functions of the dioxin receptor and its basic helix-loop-helix/PAS partner factor Arnt: inducible versus constitutive modes of regulation

1994 ◽  
Vol 14 (12) ◽  
pp. 8343-8355
Author(s):  
M L Whitelaw ◽  
J A Gustafsson ◽  
L Poellinger
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Ligand Binding ◽  
Transactivation Domain ◽  
Response Element ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
C Terminus ◽  
Heterodimeric Complex ◽  
Dioxin Receptor

Gene regulation by dioxins is mediated via the dioxin receptor, a ligand-dependent basic helix-loop-helix (bHLH)/PAS transcription factor. The latent dioxin receptor responds to dioxin signalling by forming an activated heterodimeric complex with a specific bHLH partner, Arnt, an essential process for target DNA recognition. We have analyzed the transactivating potential within this heterodimeric complex by dissecting it into individual subunits, replacing the dimerization and DNA-binding bHLH motifs with heterologous zinc finger DNA-binding domains. The uncoupled Arnt chimera, maintaining 84% of Arnt residues, forms a potent and constitutive transcription factor. Chimeric proteins show that the dioxin receptor also harbors a strong transactivation domain in the C terminus, although this activity was silenced by inclusion of 82 amino acids from the central ligand-binding portion of the dioxin receptor. This central repression region conferred binding of the molecular chaperone hsp90 upon otherwise constitutive chimeras in vitro, indicating that hsp90 has the ability to mediate a cis-repressive function on distant transactivation domains. Importantly, when the ligand-binding domain of the dioxin receptor remained intact, the ability of this hsp90-binding activity to confer repression became conditional rather than irreversible. Our data are consistent with a model in which crucial activities of the dioxin receptor, such as dimerization with Arnt and transactivation, are conditionally repressed by the central ligand- and-hsp90-binding region of the receptor. In contrast, the Arnt protein appears to be free from any repressive activity. Moreover, within the context of the dioxin response element (xenobiotic response element), the C terminus of Arnt conferred a potent, dominating transactivation function onto the native bHLH heterodimeric complex. Finally, the relative transactivation potencies of the individual dioxin receptor and Arnt chimeras varied with cell type and promoter architecture, indicating that the mechanisms for transcriptional activation may differ between these two subunits and that in the native complex the transactivation pathway may be dependent upon cell-specific and promoter contexts.

Hxt encodes a basic helix-loop-helix transcription factor that regulates trophoblast cell development

Development ◽  
1995 ◽  
Vol 121 (8) ◽  
pp. 2513-2523 ◽  
Author(s):  
J.C. Cross ◽  
M.L. Flannery ◽  
M.A. Blanar ◽  
E. Steingrimsson ◽  
N.A. Jenkins ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Gene Promoter ◽  
Giant Cells ◽  
Placental Lactogen ◽  
Specific Gene ◽  
Bhlh Transcription Factor ◽  
Trophoblast Cells ◽  
Positive Role ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix

Trophoblast cells are the first lineage to form in the mammalian conceptus and mediate the process of implantation. We report the cloning of a basic helix-loop-helix (bHLH) transcription factor gene, Hxt, that is expressed in early trophoblast and in differentiated giant cells. A separate gene, Hed, encodes a related protein that is expressed in maternal deciduum surrounding the implantation site. Overexpression of Hxt in mouse blastomeres directed their development into trophoblast cells in blastocysts. In addition, overexpression of Hxt induced the differentiation of rat trophoblast (Rcho-1) stem cells as assayed by changes in cell adhesion and by activation of the placental lactogen-I gene promoter, a trophoblast giant cell-specific gene. In contrast, the negative HLH regulator, Id-1, inhibited Rcho-1 differentiation and placental lactogen-I transcription. These data demonstrate a role for HLH factors in regulating trophoblast development and indicate a positive role for Hxt in promoting the formation of trophoblast giant cells.

scholarly journals Ras p21Val inhibits myogenesis without altering the DNA binding or transcriptional activities of the myogenic basic helix-loop-helix factors.

1995 ◽  
Vol 15 (10) ◽  
pp. 5205-5213 ◽  
Author(s):  
Y Kong ◽  
S E Johnson ◽  
E J Taparowsky ◽  
S F Konieczny
Keyword(s):  
Growth Factor ◽  
Dna Binding ◽  
Intracellular Signaling ◽  
Transcriptional Activity ◽  
Molecular Mechanisms ◽  
Terminal Differentiation ◽  
Tgf Beta ◽  
Regulatory Factors ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix

MRF4, MyoD, myogenin, and Myf-5 are muscle-specific basic helix-loop-helix transcription factors that share the ability to activate the expression of skeletal muscle genes such as those encoding alpha-actin, myosin heavy chain, and the acetylcholine receptor subunits. The muscle regulatory factors (MRFs) also exhibit the unique capacity to initiate the myogenic program when ectopically expressed in a variety of nonmuscle cell types, most notably C3H10T1/2 fibroblasts (10T1/2 cells). The commitment of myoblasts to terminal differentiation, although positively regulated by the MRFs, also is controlled negatively by a variety of agents, including several growth factors and oncoproteins such as fibroblast growth factor (FGF-2), transforming growth factor beta 1 (TGF-beta 1), and Ras p21Val. The molecular mechanisms by which these varied agents alter myogenic terminal differentiation events remain unclear. In an effort to establish whether Ras p21Val represses MRF activity by directly targeting the MRF proteins, we examined the DNA binding and transcription activation potentials of MRF4 and MyoD when expressed in 10T1/2 cells or in 10T1/2 cells expressing Ras p21Val. Our results demonstrate that Ras p21Val inhibits terminal differentiation events by targeting the basic domain of the MRFs, and yet the mechanism underlying this inhibition does not involve altering the DNA binding or the inherent transcriptional activity of these regulatory factors. In contrast, FGF-2 and TGF-beta 1 block terminal differentiation by repressing the transcriptional activity of the MRFs. We conclude that the Ras p21Val block in differentiation operates via an intracellular signaling pathway that is distinct from the FGF-2 and TGF-beta 1 pathways.

scholarly journals mTFE3, an X-linked transcriptional activator containing basic helix-loop-helix and zipper domains, utilizes the zipper to stabilize both DNA binding and multimerization.

1992 ◽  
Vol 12 (2) ◽  
pp. 817-827 ◽  
Author(s):  
C Roman ◽  
A G Matera ◽  
C Cooper ◽  
S Artandi ◽  
S Blain ◽  
...  
Keyword(s):  
Dna Binding ◽  
Heavy Chain ◽  
Leucine Zipper ◽  
Immunoglobulin Heavy Chain ◽  
Functional Roles ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
The Individual ◽  
Bhlh Proteins ◽  
High Degree

Southwestern (DNA-protein) screening of a murine L-cell cDNA library by using a probe for the microE3 site in the immunoglobulin heavy-chain enhancer yielded a clone, mTFE3, which is a member of the subset of basic helix-loop-helix (BHLH) proteins that also contain a leucine zipper (ZIP). Since the individual contribution of these domains is not well understood for proteins which contain them both, mutational analyses were performed to assess the functional roles of the HLH and ZIP regions for DNA binding and multimerization. The HLH region is stringently required for DNA binding but not for multimerization. The ZIP region is not stringently required for binding or multimerization, but stabilizes both multimer formation and DNA binding. A high degree of conservation at both the amino acid and nucleotide levels between the human transcription factor TFE3 and mTFE3 suggests that mTFE3 is the murine homolog of human TFE3. By using fluorescent in situ hybridization, mTFE3 was mapped to mouse chromosome X in band A2, which is just below the centromere. We show that in addition to the immunoglobulin heavy-chain microE3 site, mTFE3 binds to transcriptional elements important for lymphoid-specific, muscle-specific, and ubiquitously expressed genes. Binding of mTFE3 to DNA induces DNA bending.

DNA Binding Specificity of the Basic-Helix-Loop-Helix Protein MASH-1

Biochemistry ◽  
1995 ◽  
Vol 34 (35) ◽  
pp. 11026-11036 ◽  
Author(s):  
Daniel Meierhans ◽  
Chirine el-Ariss ◽  
Margrit Neuenschwander ◽  
Martin Sieber ◽  
Joseph F. Stackhouse ◽  
...  
Keyword(s):  
Dna Binding ◽  
Binding Specificity ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Dna Binding Specificity

scholarly journals Conformational activation of a basic helix-loop-helix protein (MyoD1) by the C-terminal region of murine HSP90 (HSP84).

1992 ◽  
Vol 12 (11) ◽  
pp. 5059-5068 ◽  
Author(s):  
R Shaknovich ◽  
G Shue ◽  
D S Kohtz
Keyword(s):  
Dna Binding ◽  
Direct Evidence ◽  
Conformational Structure ◽  
Amphipathic Helix ◽  
Expression Library ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Transient Interaction ◽  
Dose Dependent Fashion ◽  
Dose Dependent

A murine cardiac lambda gt11 expression library was screened with an amphipathic helix antibody, and a recombinant representing the C-terminal 194 residues of murine HSP90 (HSP84) was cloned. Both recombinant and native HSP90s were then found to rapidly convert a basic helix-loop-helix protein (MyoD1) from an inactive to an active conformation, as assayed by sequence-specific DNA binding. The conversion process involves a transient interaction between HSP90 and MyoD1 and does not result in the formation of a stable tertiary complex. Conversion does not require ATP and occurs stoichiometrically in a dose-dependent fashion. HSP90 is an abundant, ubiquitous, and highly conserved protein present in most eukaryotic cells. These results provide direct evidence that HSP90 can affect the conformational structure of a DNA-binding protein.

scholarly journals Myc phosphorylation in its basic helix–loop–helix region destabilizes transient α-helical structures, disrupting Max and DNA binding

2018 ◽  
Vol 293 (24) ◽  
pp. 9301-9310 ◽  
Author(s):  
Pavel Macek ◽  
Matthew J. Cliff ◽  
Kevin J. Embrey ◽  
Geoffrey A. Holdgate ◽  
J. Willem M. Nissink ◽  
...  
Keyword(s):  
Dna Binding ◽  
Helical Structures ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix

scholarly journals Regulatory domains of the A-Myb transcription factor and its interaction with the CBP/p300 adaptor molecules

1997 ◽  
Vol 324 (3) ◽  
pp. 729-736 ◽  
Author(s):  
Valeria FACCHINETTI ◽  
Livio LOFFARELLI ◽  
Sabine SCHREEK ◽  
Michael OELGESCHLÄGER ◽  
Bernhard LÜSCHER ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Binding Protein ◽  
Camp Response Element Binding ◽  
Binding Activity ◽  
Myb Transcription Factor ◽  
Physical Interaction ◽  
Creb Binding Protein ◽  
Activation Domain ◽  
Activation Potential

The A-Myb transcription factor belongs to the Myb family of oncoproteins and is likely to be involved in the regulation of proliferation and/or differentiation of normal B cells and Burkitt's lymphoma cells. To characterize in detail the domains of A-Myb that regulate its function, we have generated a series of deletion mutants and have investigated their trans-activation potential as well as their DNA-binding activity. Our results have allowed us to delineate the trans-activation domain as well as two separate regulatory regions. The boundaries of the trans-activation domain (amino acid residues 218–319) are centred on a sequence rich in charged amino acids (residues 259–281). A region (residues 320–482) localized immediately downstream of the trans-activation domain and containing a newly identified conserved stretch of 48 residues markedly inhibits specific DNA binding. Finally the last 110 residues of A-Myb (residues 643–752), which include a sequence conserved in all mammalian myb genes (region III), negatively regulate the maximal trans-activation potential of A-Myb. We have also investigated the functional interaction between A-Myb and the nuclear adaptor molecule CBP [cAMP response element-binding protein (CREB)-binding protein]. We demonstrate that CBP synergizes with A-Myb in a dose-dependent fashion, and that this co-operative effect can be inhibited by E1A and can also be observed with the CBP homologue p300. We show that this functional synergism requires the presence of the A-Myb charged sequence and that it involves physical interaction between A-Myb and the CREB-binding domain of CBP.

Sign in / Sign up

Export Citation Format

Share Document