scholarly journals SREBP-2, a second basic-helix-loop-helix-leucine zipper protein that stimulates transcription by binding to a sterol regulatory element.

1993 ◽  
Vol 90 (24) ◽  
pp. 11603-11607 ◽  
Author(s):  
X. Hua ◽  
C. Yokoyama ◽  
J. Wu ◽  
M. R. Briggs ◽  
M. S. Brown ◽  
...  
Keyword(s):  
Leucine Zipper ◽  
Regulatory Element ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Sterol Regulatory Element ◽  
Leucine Zipper Protein

scholarly journals Nuclear Import of Sterol Regulatory Element–binding Protein-2, a Basic Helix-Loop-Helix–Leucine Zipper (bHLH-Zip)–containing Transcription Factor, Occurs through the Direct Interaction of Importin β with HLH-Zip

1999 ◽  
Vol 10 (7) ◽  
pp. 2221-2233 ◽  
Author(s):  
Emi Nagoshi ◽  
Naoko Imamoto ◽  
Ryuichiro Sato ◽  
Yoshihiro Yoneda
Keyword(s):  
Nuclear Import ◽  
Leucine Zipper ◽  
Binding Protein ◽  
Regulatory Element ◽  
Endoplasmic Reticulum Membrane ◽  
Transport Pathway ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Element Binding Protein ◽  
Sterol Regulatory Element

The sterol regulatory element–binding protein-2 (SREBP-2) is produced as a large precursor molecule attached to the endoplasmic reticulum membrane. In response to the sterol depletion, the N-terminal segment of the precursor, which contains a basic helix-loop-helix–leucine zipper domain, is released by two sequential cleavages and is translocated to the nucleus, where it activates the transcription of target genes. The data herein show that released SREBP-2 uses a distinct nuclear transport pathway, which is mediated by importin β. The mature form of SREBP-2 is actively transported into the nucleus when injected into the cell cytoplasm. SREBP-2 binds directly to importin β in the absence of importin α. Ran-GTP but not Ran-GDP causes the dissociation of the SREBP-2–importin β complex. G19VRan-GTP inhibits the nuclear import of SREBP-2 in living cells. In the permeabilized cell in vitro transport system, nuclear import of SREBP-2 is reconstituted only by importin β in conjunction with Ran and its interacting protein p10/NTF2. We further demonstrate that the helix-loop-helix–leucine zipper motif of SREBP-2 contains a novel type of nuclear localization signal, which binds directly to importin β.

scholarly journals An Arabidopsis Basic Helix-Loop-Helix Leucine Zipper Protein Modulates Metal Homeostasis and Auxin Conjugate Responsiveness

Genetics ◽  
2006 ◽  
Vol 174 (4) ◽  
pp. 1841-1857 ◽  
Author(s):  
Rebekah A. Rampey ◽  
Andrew W. Woodward ◽  
Brianne N. Hobbs ◽  
Megan P. Tierney ◽  
Brett Lahner ◽  
...  
Keyword(s):  
Leucine Zipper ◽  
Metal Homeostasis ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix ◽  
Leucine Zipper Protein

scholarly journals Dimerization of Sterol Regulatory Element-Binding Protein 2 via the Helix-Loop-Helix-Leucine Zipper Domain Is a Prerequisite for Its Nuclear Localization Mediated by Importin β

2001 ◽  
Vol 21 (8) ◽  
pp. 2779-2789 ◽  
Author(s):  
Emi Nagoshi ◽  
Yoshihiro Yoneda
Keyword(s):  
Nuclear Import ◽  
Leucine Zipper ◽  
Binding Protein ◽  
Regulatory Element ◽  
Active Form ◽  
Proteolytic Processing ◽  
Helix Loop Helix ◽  
Zip Family ◽  
Element Binding Protein ◽  
Sterol Regulatory Element

ABSTRACT The sterol regulatory element-binding protein 2 (SREBP-2), a transcription factor of the basic helix-loop-helix-leucine zipper (bHLH-Zip) family, is synthesized in the form of a membrane-attached precursor molecule. When cells are deprived of sterols, a two-step proteolytic processing releases the transcriptionally active N-terminal segment of SREBP-2, thereby allowing it to enter the nucleus. In previous studies, we showed that the nuclear import of SREBP-2 occurs via the direct interaction of importin β with the HLH-Zip domain. In this study, in order to more completely understand the intracellular dynamics of SREBP-2, we focused on the manner by which importin β recognizes SREBP-2 at the initial step of the import. It was found that the active form of SREBP-2 exists as a stable dimer in solution and that the substitution of leucine residues for alanine in the leucine zipper motif disrupted the dimerization. It was also demonstrated that this mutant protein did not enter the nucleus either in vivo or in vitro. Solution binding assays, which involved the chemical cross-linking of wild-type or mutated SREBP-2 with importin β, revealed that the import-active complex appeared to be composed of a dimeric form of SREBP-2 and importin β. In addition, the SREBP-2 binding domain of importin β corresponded to an overlapping but not identical region for importin α binding, which may explain how importin β is able to recognize the dimeric HLH-Zip directly. These results indicate that dimerization is a prerequisite process for the nuclear import of SREBP-2 mediated by importin β.

scholarly journals The Basic Helix-Loop-Helix Transcription Factor Cph2 Regulates Hyphal Development in CandidaalbicansPartly via Tec1

2001 ◽  
Vol 21 (19) ◽  
pp. 6418-6428 ◽  
Author(s):  
Shelley Lane ◽  
Song Zhou ◽  
Ting Pan ◽  
Qian Dai ◽  
Haoping Liu
Keyword(s):  
Transcription Factor ◽  
Protein Kinase ◽  
Binding Sites ◽  
Regulatory Element ◽  
Ectopic Expression ◽  
Mitogen Activated Protein Kinase ◽  
Northern Analysis ◽  
Hyphal Development ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix

ABSTRACT Candida albicans undergoes a morphogenetic switch from budding yeast to hyphal growth form in response to a variety of stimuli and growth conditions. Multiple signaling pathways, including a Cph1-mediated mitogen-activated protein kinase pathway and an Efg1-mediated cyclic AMP/protein kinase A pathway, regulate the transition. Here we report the identification of a basic helix-loop-helix transcription factor of the Myc subfamily (Cph2) by its ability to promote pseudohyphal growth inSaccharomyces cerevisiae. Like sterol response element binding protein 1, Cph2 has a Tyr instead of a conserved Arg in the basic DNA binding region. Cph2 regulates hyphal development in C. albicans, ascph2/cph2 mutant strains show medium-specific impairment in hyphal development and in the induction of hypha-specific genes. However, many hypha-specific genes do not have potential Cph2 binding sites in their upstream regions. Interestingly, upstream sequences of all known hypha-specific genes are found to contain potential binding sites for Tec1, a regulator of hyphal development. Northern analysis shows that TEC1 transcription is highest in the medium in which cph2/cph2 displays a defect in hyphal development, and Cph2 is necessary for this transcriptional induction of TEC1. In vitro gel mobility shift experiments show that Cph2 directly binds to the two sterol regulatory element 1-like elements upstream of TEC1. Furthermore, the ectopic expression of TEC1 suppresses the defect ofcph2/cph2 in hyphal development. Therefore, the function of Cph2 in hyphal transcription is mediated, in part, through Tec1. We further show that this function of Cph2 is independent of the Cph1- and Efg1-mediated 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.

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