1
|
Sadeghi F, Kardar GA, Bolouri MR, Nasri F, Sadri M, Falak R. Overexpression of bHLH domain of HIF-1 failed to inhibit the HIF-1 transcriptional activity in hypoxia. Biol Res 2020; 53:25. [PMID: 32503642 PMCID: PMC7275393 DOI: 10.1186/s40659-020-00293-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 05/18/2020] [Indexed: 01/22/2023] Open
Abstract
Background Hypoxia inducible factor-1 (HIF-1) is considered as the most activated transcriptional factor in response to low oxygen level or hypoxia. HIF-1 binds the hypoxia response element (HRE) sequence in the promoter of different genes, mainly through the bHLH domain and activates the transcription of genes, especially those involved in angiogenesis and EMT. Considering the critical role of bHLH in binding HIF-1 to the HRE sequence, we hypothesized that bHLH could be a promising candidate to be targeted in hypoxia condition. Methods We inserted an inhibitory bHLH (ibHLH) domain in a pIRES2-EGFP vector and transfected HEK293T cells with either the control vector or the designed construct. The ibHLH domain consisted of bHLH domains of both HIF-1a and Arnt, capable of competing with HIF-1 in binding to HRE sequences. The transfected cells were then treated with 200 µM of cobalt chloride (CoCl2) for 48 h to induce hypoxia. Real-time PCR and western blot were performed to evaluate the effect of ibHLH on the genes and proteins involved in angiogenesis and EMT. Results Hypoxia was successfully induced in the HEK293T cell line as the gene expression of VEGF, vimentin, and β-catenin were significantly increased after treatment of untransfected HEK293T cells with 200 µM CoCl2. The gene expression of VEGF, vimentin, and β-catenin and protein level of β-catenin were significantly decreased in the cells transfected with either control or ibHLH vectors in hypoxia. However, ibHLH failed to be effective on these genes and the protein level of β-catenin, when compared to the control vector. We also observed that overexpression of ibHLH had more inhibitory effect on gene and protein expression of N-cadherin compared to the control vector. However, it was not statistically significant. Conclusion bHLH has been reported to be an important domain involved in the DNA binding activity of HIF. However, we found that targeting this domain is not sufficient to inhibit the endogenous HIF-1 transcriptional activity. Further studies about the function of critical domains of HIF-1 are necessary for developing a specific HIF-1 inhibitor.
Collapse
Affiliation(s)
- Fatemeh Sadeghi
- Immunology Research Center, Iran University of Medical Sciences, Tehran, Iran.,Department of Immunology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Gholam Ali Kardar
- Immunology Asthma & Allergy Research Institute, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran.
| | - Mohammad Reza Bolouri
- Immunology Research Center, Iran University of Medical Sciences, Tehran, Iran.,Department of Immunology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Farzad Nasri
- Immunology Research Center, Iran University of Medical Sciences, Tehran, Iran.,Department of Immunology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Maryam Sadri
- Immunology Research Center, Iran University of Medical Sciences, Tehran, Iran.,Department of Immunology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Reza Falak
- Immunology Research Center, Iran University of Medical Sciences, Tehran, Iran. .,Department of Immunology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
| |
Collapse
|
2
|
Susanto AH, Widodo, Rohman MS, Utomo DH, Lukitasari M. Analysis in silico of the single nucleotide polymorphism G–152A in the promoter of the angiotensinogen gene of Indonesian patients with essential hypertension. ASIAN BIOMED 2018. [DOI: 10.1515/abm-2018-0027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Background
Single nucleotide polymorphism (SNP) G–152A (rs11568020) in the promoter of the angiotensinogen gene (AGT) may modulate its transcription. Translation of mRNA to angiotensinogen induces hypertension during hypoxia. The G allele at position –152 is located within the hypoxia-response element (HRE) transcription factor-binding site for the hypoxia-inducible factor 1 (HIF-1) heterodimer. However, the function of the –152 site in HIF-1 binding is not fully elucidated.
Objectives
To determine the frequency of SNP G–152A in Indonesian patients with hypertension and the function of this SNP.
Methods
We determined the frequency of the SNP in 100 patients by direct sequencing, and the influence of SNP G–152A on predicted binding of HIF-1 to the HRE using a docking approach in silico.
Results
The AGT promoter in our patients had genetic variants –152G and –152A (19:1). Predicted binding indicated that HIF-1 directly contacts the major groove of the G allele, but not the A allele. Scoring according to weighted sum High Ambiguity Driven biomolecular DOCKing showed that the score for the A allele–HIF-1 complex (–47.1 ± 6.9 kcal/mol) was higher than that for the G allele–HIF-1 complex (–94.6 ± 14.1 kcal/mol), indicating more favorable binding of HIF-1 to the G allele.
Conclusions
SNP G–152A reduces the favorability of binding of HIF-1 to the HRE. The occurrence of this SNP in the AGT promoter of Indonesian patients with essential hypertension suggests that the G allele is a genetic susceptibility factor in hypertension regulated by HIF-1.
Collapse
Affiliation(s)
- Akhiyan Hadi Susanto
- Basic Nursing Department , School of Nursing, Faculty of Medicine , Universitas Brawijaya , Malang 65145 , Indonesia
| | - Widodo
- Biology Department , Faculty of Mathematics and Natural Sciences , Universitas Brawijaya , Malang 65145 , Indonesia
| | - Mohammad Saifur Rohman
- Department of Cardiology and Vascular Medicine , Faculty of Medicine , Universitas Brawijaya – Saiful Anwar General Hospital , Malang 65145 , Indonesia
| | - Didik Huswo Utomo
- Biology Department , Faculty of Mathematics and Natural Sciences , Universitas Brawijaya , Malang 65145 , Indonesia
| | - Mifetika Lukitasari
- Medical Surgical Nursing Department , School of Nursing, Faculty of Medicine , Universitas Brawijaya , Malang 65145 , Indonesia
| |
Collapse
|
3
|
Gálvez H, Tena JJ, Giraldez F, Abelló G. The Repression of Atoh1 by Neurogenin1 during Inner Ear Development. Front Mol Neurosci 2017; 10:321. [PMID: 29104531 PMCID: PMC5655970 DOI: 10.3389/fnmol.2017.00321] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 09/21/2017] [Indexed: 01/01/2023] Open
Abstract
Atonal homolog 1 (Atoh1) and Neurogenin1 (Neurog1) are basic Helix-Loop-Helix (bHLH) transcription factors crucial for the generation of hair cells (HCs) and neurons in the inner ear. Both genes are induced early in development, but the expression of Atoh1 is counteracted by Neurog1. As a result, HC development is prevented during neurogenesis. This work aimed at understanding the molecular basis of this interaction. Atoh1 regulation depends on a 3'Atoh1-enhancer that is the site for Atoh1 autoregulation. Reporter assays on chick embryos and P19 cells show that Neurog1 hampers the autoactivation of Atoh1, the effect being cell autonomous and independent on Notch activity. Assay for Transposase-Accessible Chromatin with high throughput sequencing (ATAC-Seq) analysis shows that the region B of the 3'Atoh1-enhancer is accessible during development and sufficient for both activation and repression. Neurog1 requires the regions flanking the class A E-box to show its repressor effect, however, it does not require binding to DNA for Atoh1 repression. This depends on the dimerization domains Helix-1 and Helix-2 and the reduction of Atoh1 protein levels. The results point towards the acceleration of Atoh1 mRNA degradation as the potential mechanism for the reduction of Atoh1 levels. Such a mechanism dissociates the prevention of Atoh1 expression in neurosensory progenitors from the unfolding of the neurogenic program.
Collapse
Affiliation(s)
- Héctor Gálvez
- DCEXS, Universitat Pompeu Fabra (UPF) - Parc de Recerca Biomèdica de Barcelona (PRBB), Barcelona, Spain
| | - Juan J Tena
- Centro Andaluz de Biología del Desarrollo, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain
| | - Fernando Giraldez
- DCEXS, Universitat Pompeu Fabra (UPF) - Parc de Recerca Biomèdica de Barcelona (PRBB), Barcelona, Spain
| | - Gina Abelló
- DCEXS, Universitat Pompeu Fabra (UPF) - Parc de Recerca Biomèdica de Barcelona (PRBB), Barcelona, Spain
| |
Collapse
|
4
|
Abstract
SCL, a transcription factor of the basic helix-loop-helix family, is a master regulator of hematopoiesis. Scl specifies lateral plate mesoderm to a hematopoietic fate and establishes boundaries by inhibiting the cardiac lineage. A combinatorial interaction between Scl and Vegfa/Flk1 sets in motion the first wave of primitive hematopoiesis. Subsequently, definitive hematopoietic stem cells (HSCs) emerge from the embryo proper via an endothelial-to-hematopoietic transition controlled by Runx1, acting with Scl and Gata2. Past this stage, Scl in steady state HSCs is redundant with Lyl1, a highly homologous factor. However, Scl is haploinsufficient in stress response, when a rare subpopulation of HSCs with very long term repopulating capacity is called into action. SCL activates transcription by recruiting a core complex on DNA that necessarily includes E2A/HEB, GATA1-3, LIM-only proteins LMO1/2, LDB1, and an extended complex comprising ETO2, RUNX1, ERG, or FLI1. These interactions confer multifunctionality to a complex that can control cell proliferation in erythroid progenitors or commitment to terminal differentiation through variations in single component. Ectopic SCL and LMO1/2 expression in immature thymocytes activates of a stem cell gene network and reprogram cells with a finite lifespan into self-renewing preleukemic stem cells (pre-LSCs), an initiating event in T-cell acute lymphoblastic leukemias. Interestingly, fate conversion of fibroblasts to hematoendothelial cells requires not only Scl and Lmo2 but also Gata2, Runx1, and Erg, indicating a necessary collaboration between these transcription factors for hematopoietic reprogramming. Nonetheless, full reprogramming into self-renewing multipotent HSCs may require additional factors and most likely, a permissive microenvironment.
Collapse
Affiliation(s)
- T Hoang
- Laboratory of Hematopoiesis and Leukemia, Institute of Research in Immunology and Cancer (IRIC), University of Montreal, Montreal, QC, Canada.
| | - J A Lambert
- Laboratory of Hematopoiesis and Leukemia, Institute of Research in Immunology and Cancer (IRIC), University of Montreal, Montreal, QC, Canada
| | - R Martin
- Laboratory of Hematopoiesis and Leukemia, Institute of Research in Immunology and Cancer (IRIC), University of Montreal, Montreal, QC, Canada
| |
Collapse
|
5
|
Abstract
Understanding the diversification of dendritic cell (DC) lineages is one of the last frontiers in mapping the developmental hierarchy of the hematopoietic system. DCs are a vital link between the innate and adaptive immune responses; thus, elucidating their developmental pathways is crucial for insight into the generation of natural immunity and for learning how to regulate DCs in clinical settings. DCs arise from hematopoietic stem cells through specialized progenitor subsets under the direction of FMS-like tyrosine kinase 3 ligand (Flt3L) and Flt3L receptor (Flt3) signaling. Recent studies have revealed important contributions from granulocyte-macrophage colony-stimulating factor (GM-CSF) and type I interferons (IFNs) in vivo. Furthermore, DC development is guided by lineage-restricted transcription factors such as IRF8, E2-2, and Batf3. A critical question centers on how cytokines and lineage-restricted transcription factors operate molecularly to direct DC diversification. Here, we review recent findings that provide new insight into the DC developmental process.
Collapse
Affiliation(s)
- Stephanie S Watowich
- Department of Immunology and Center for Cancer Immunology Research, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
| | | |
Collapse
|
6
|
Tanaka A, Itoh F, Itoh S, Kato M. TAL1/SCL relieves the E2-2-mediated repression of VEGFR2 promoter activity. J Biochem 2008; 145:129-35. [PMID: 19029143 DOI: 10.1093/jb/mvn158] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The basic helix-loop-helix (bHLH) protein TAL1/SCL is essential for embryonic-vascular development. TAL1/SCL regulates the activation of endothelial cells by binding directly or indirectly to DNA sequences in critical target genes. We recently demonstrated that E-box protein E2-2 blocks endothelial cell activation via perturbation of VEGFR2 promoter activity. Herein, we report that TAL1/SCL interacts with E2-2 and inhibits E2-2-mediated effects on reporter activity. Mutational analysis revealed that the HLH domain of TAL1/SCL, but not its basic region, is required for interaction with E2-2. Importantly, TAL1/SCL relieves the E2-2-mediated repression of VEGFR2 reporter activity in endothelial cells. Our data elaborate on the bHLH protein interactions that regulate endothelial cell activation.
Collapse
Affiliation(s)
- Aya Tanaka
- Department of Experimental Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
| | | | | | | |
Collapse
|
7
|
Palomero T, Odom DT, O'Neil J, Ferrando AA, Margolin A, Neuberg DS, Winter SS, Larson RS, Li W, Liu XS, Young RA, Look AT. Transcriptional regulatory networks downstream of TAL1/SCL in T-cell acute lymphoblastic leukemia. Blood 2006; 108:986-92. [PMID: 16621969 PMCID: PMC1895859 DOI: 10.1182/blood-2005-08-3482] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aberrant expression of 1 or more transcription factor oncogenes is a critical component of the molecular pathogenesis of human T-cell acute lymphoblastic leukemia (T-ALL); however, oncogenic transcriptional programs downstream of T-ALL oncogenes are mostly unknown. TAL1/SCL is a basic helix-loop-helix (bHLH) transcription factor oncogene aberrantly expressed in 60% of human T-ALLs. We used chromatin immunoprecipitation (ChIP) on chip to identify 71 direct transcriptional targets of TAL1/SCL. Promoters occupied by TAL1 were also frequently bound by the class I bHLH proteins E2A and HEB, suggesting that TAL1/E2A as well as TAL1/HEB heterodimers play a role in transformation of T-cell precursors. Using RNA interference, we demonstrated that TAL1 is required for the maintenance of the leukemic phenotype in Jurkat cells and showed that TAL1 binding can be associated with either repression or activation of genes whose promoters occupied by TAL1, E2A, and HEB. In addition, oligonucleotide microarray analysis of RNA from 47 primary T-ALL samples showed specific expression signatures involving TAL1 targets in TAL1-expressing compared with -nonexpressing human T-ALLs. Our results indicate that TAL1 may act as a bifunctional transcriptional regulator (activator and repressor) at the top of a complex regulatory network that disrupts normal T-cell homeostasis and contributes to leukemogenesis.
Collapse
Affiliation(s)
- Teresa Palomero
- Institute for Cancer Genetics, Columbia University, 1150 St Nicholas Ave, New York, NY 10032, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Xie Y, Massa SM, Ensslen-Craig SE, Major DL, Yang T, Tisi MA, Derevyanny VD, Runge WO, Mehta BP, Moore LA, Brady-Kalnay SM, Longo FM. Protein-tyrosine phosphatase (PTP) wedge domain peptides: a novel approach for inhibition of PTP function and augmentation of protein-tyrosine kinase function. J Biol Chem 2006; 281:16482-92. [PMID: 16613844 DOI: 10.1074/jbc.m603131200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Inhibition of protein-tyrosine phosphatases (PTPs) counterbalancing protein-tyrosine kinases (PTKs) offers a strategy for augmenting PTK actions. Conservation of PTP catalytic sites limits development of specific PTP inhibitors. A number of receptor PTPs, including the leukocyte common antigen-related (LAR) receptor and PTPmu, contain a wedge-shaped helix-loop-helix located near the first catalytic domain. Helix-loop-helix domains in other proteins demonstrate homophilic binding and inhibit function; therefore, we tested the hypothesis that LAR wedge domain peptides would exhibit homophilic binding, bind to LAR, and inhibit LAR function. Fluorescent beads coated with LAR or PTPmu wedge peptides demonstrated PTP-specific homophilic binding, and LAR wedge peptide-coated beads precipitated LAR protein. Administration of LAR wedge Tat peptide to PC12 cells resulted in increased proliferation, decreased cell death, increased neurite outgrowth, and augmented Trk PTK-mediated responses to nerve growth factor (NGF), a phenotype matching that found in PC12 cells with reduced LAR levels. PTPmu wedge Tat peptide had no effect on PC12 cells but blocked the PTPmu-dependent phenotype of neurite outgrowth of retinal ganglion neurons on a PTPmu substrate, whereas LAR wedge peptide had no effect. The survival- and neurite-promoting effect of the LAR wedge peptide was blocked by the Trk inhibitor K252a, and reciprocal co-immunoprecipitation demonstrated LAR/TrkA association. The addition of LAR wedge peptide inhibited LAR co-immunoprecipitation with TrkA, augmented NGF-induced activation of TrkA, ERK, and AKT, and in the absence of exogenous NGF, induced activation of TrkA, ERK, and AKT. PTP wedge domain peptides provide a unique PTP inhibition strategy and offer a novel approach for augmenting PTK function.
Collapse
Affiliation(s)
- Youmei Xie
- Department of Neurology, University of North Carolina, Chapel Hill, NC 27599, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Ciarapica R, Rosati J, Cesareni G, Nasi S. Molecular recognition in helix-loop-helix and helix-loop-helix-leucine zipper domains. Design of repertoires and selection of high affinity ligands for natural proteins. J Biol Chem 2003; 278:12182-90. [PMID: 12514181 DOI: 10.1074/jbc.m211991200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Helix-loop-helix (HLH) and helix-loop-helix-leucine zipper (HLHZip) are dimerization domains that mediate selective pairing among members of a large transcription factor family involved in cell fate determination. To investigate the molecular rules underlying recognition specificity and to isolate molecules interfering with cell proliferation and differentiation control, we assembled two molecular repertoires obtained by directed randomization of the binding surface in these two domains. For this strategy we selected the Heb HLH and Max Zip regions as molecular scaffolds for the randomization process and displayed the two resulting molecular repertoires on lambda phage capsids. By affinity selection, many domains were isolated that bound to the proteins Mad, Rox, MyoD, and Id2 with different levels of affinity. Although several residues along an extended surface within each domain appeared to contribute to dimerization, some key residues critically involved in molecular recognition could be identified. Furthermore, a number of charged residues appeared to act as switch points facilitating partner exchange. By successfully selecting ligands for four of four HLH or HLHZip proteins, we have shown that the repertoires assembled are rather general and possibly contain elements that bind with sufficient affinity to any natural HLH or HLHZip molecule. Thus they represent a valuable source of ligands that could be used as reagents for molecular dissection of functional regulatory pathways.
Collapse
Affiliation(s)
- Roberta Ciarapica
- Istituto di Biologia and Patologia Molecolari Consiglio Nazionale delle Ricerche, Università La Sapienza, 00185 Roma, Italy
| | | | | | | |
Collapse
|
10
|
Michel G, Minet E, Ernest I, Roland I, Durant F, Remacle J, Michiels C. A model for the complex between the hypoxia-inducible factor-1 (HIF-1) and its consensus DNA sequence. J Biomol Struct Dyn 2000; 18:169-79. [PMID: 11089639 DOI: 10.1080/07391102.2000.10506656] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Hypoxia-inducible factor-1 (HIF-1) is a heterodimeric transcription factor activated by hypoxia. When activated, HIF-1 mediates the differential expression of genes such as erythropoietin and Vascular Endothelial Growth Factor (VEGF) during hypoxia. It is composed of two different subunits, HIF-1alpha and ARNT (Aryl Receptor Nuclear Translocator). These two subunits belong to the bHLH (basic Helix-Loop-Helix) PAS (Per, Ahr/ARNT, Sim) family. The bHLH domain of these factors is responsible for dimerization through the two helices and for DNA binding through their basic domain. In this work, we used various methods of molecular modeling in order to develop a 3D structure for the HIF-1 bHLH domain bound to its DNA consensus sequence. Firstly, the 3D structure of the bHLH domain of both subunits based on their amino acid sequence was defined. Secondly, we compared this model with data from known crystal structures of basic leucine zipper-DNA and bHLH-DNA complexes in order to determine a potential canvas for HIF-1. Thirdly, we performed a manual approach of the HIF-1 bHLH domain onto the DNA recognition site using this canvas. Finally, the protein-DNA complex 3D structure was optimized using a Monte Carlo program called MONTY. The model predicted a pattern of interactions between amino acids and DNA bases which reflect for ARNT what is experimentally observed among different X-ray structures of other bHLH transcription factors possessing the H (His), E (Glu), R (Arg) triad, as ARNT does. On the other hand, only the Arg residue is conserved in HIF- 1alpha. We propose from this model that a serine replaces the histidine while an alanine and a lysine also make contacts with DNA. From these results, we postulate that the specificity of HIF-1 toward its DNA sequence could be driven by the HIF-1alpha subunit. The predicted model will be verified by X-Ray currently ongoing.
Collapse
Affiliation(s)
- G Michel
- Laboratoire de Chimie Moléculaire Structurale, Facultés Universitaires, Notre-Dame-de-la-Paix, Namur, Belgium.
| | | | | | | | | | | | | |
Collapse
|
11
|
Liu J, Shi W, Warburton D. A cysteine residue in the helix-loop-helix domain of Id2 is critical for homodimerization and function. Biochem Biophys Res Commun 2000; 273:1042-7. [PMID: 10891368 DOI: 10.1006/bbrc.2000.3055] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Id proteins are negative regulators of basic helix-loop-helix (bHLH) transcription factors. In this study, we compared the expression of Id2 mRNA in proliferating (fetal) and nonproliferating (adult) alveolar epithelial cells (AECs). The expression of Id2 was higher in adult AECs than in the corresponding fetal cells, suggesting that Id2 might play a functional role in developmental regulation of lung epithelial cell proliferation. By screening a mouse embryo cDNA library in the yeast two-hybrid system, Id2 was identified as a self-associating protein. Structural analysis by deletion and site-directed mutagenesis demonstrated that the HLH domain and a cysteine residue within the HLH domain are essential for Id2 homodimerization. Furthermore, in vitro synthesized Id2 homodimers became monomers under reducing conditions, indicating that the formation of an intermolecular disulfide bond is critical for Id2 homodimerization. Transient transfection assays in A549 cells showed that wild-type Id2 down-regulated the activity of the cyclin A promoter by 70%, while mutating the cysteine critical for Id2 homodimerization abolished the inhibitory effect of wild-type Id2.
Collapse
Affiliation(s)
- J Liu
- Developmental Biology Program, Division of Pediatric Surgery, Childrens Hospital Los Angeles, University of Southern California, Keek School of Medicine, 4650 Sunset Boulevard, Los Angeles, California 90027, USA
| | | | | |
Collapse
|
12
|
Chervinsky DS, Zhao XF, Lam DH, Ellsworth M, Gross KW, Aplan PD. Disordered T-cell development and T-cell malignancies in SCL LMO1 double-transgenic mice: parallels with E2A-deficient mice. Mol Cell Biol 1999; 19:5025-35. [PMID: 10373552 PMCID: PMC84335 DOI: 10.1128/mcb.19.7.5025] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gene most commonly activated by chromosomal rearrangements in patients with T-cell acute lymphoblastic leukemia (T-ALL) is SCL/tal. In collaboration with LMO1 or LMO2, the thymic expression of SCL/tal leads to T-ALL at a young age with a high degree of penetrance in transgenic mice. We now show that SCL LMO1 double-transgenic mice display thymocyte developmental abnormalities in terms of proliferation, apoptosis, clonality, and immunophenotype prior to the onset of a frank malignancy. At 4 weeks of age, thymocytes from SCL LMO1 mice show 70% fewer total thymocytes, with increased rates of both proliferation and apoptosis, than control thymocytes. At this age, a clonal population of thymocytes begins to populate the thymus, as evidenced by oligoclonal T-cell-receptor gene rearrangements. Also, there is a dramatic increase in immature CD44(+) CD25(-) cells, a decrease in the more mature CD4(+) CD8(+) cells, and development of an abnormal CD44(+) CD8(+) population. An identical pattern of premalignant changes is seen with either a full-length SCL protein or an amino-terminal truncated protein which lacks the SCL transactivation domain, demonstrating that the amino-terminal portion of SCL is not important for leukemogenesis. Lastly, we show that the T-ALL which develop in the SCL LMO1 mice are strikingly similar to those which develop in E2A null mice, supporting the hypothesis that SCL exerts its oncogenic action through a functional inactivation of E proteins.
Collapse
Affiliation(s)
- D S Chervinsky
- Departments of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | | | | | | | | | | |
Collapse
|
13
|
Zhao XF, Aplan PD. The hematopoietic transcription factor SCL binds the p44 subunit of TFIIH. J Biol Chem 1999; 274:1388-93. [PMID: 9880511 DOI: 10.1074/jbc.274.3.1388] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SCL is a basic domain helix-loop-helix (bHLH) oncoprotein that is involved in T-cell acute lymphoblastic leukemia as well as in normal hematopoiesis. Although it is believed that SCL functions as a tissue-specific transcription factor, no molecular mechanism has thus far been identified for this putative function. In this report, we show that SCL interacts with p44, a subunit of the basal transcription factor TFIIH. The minimal region of SCL that interacts with p44 was mapped to a 101-amino acid sequence that includes, but is not limited to, the bHLH region; the SCL-binding site of p44 is located in the carboxyl-terminal half of p44. This interaction was confirmed by glutathione S-transferase fusion protein pull-down assays and a co-immunoprecipitation assay. As analyzed with a yeast two-hybrid system, p44 interacts specifically with SCL, but not with the other class A or B bHLH proteins tested. E2A did not compete with p44 for SCL binding, as demonstrated by an in vitro binding assay. These findings document a previously unsuspected interaction between SCL and a subunit of the basal transcription factor TFIIH, suggesting a potential means by which SCL might modulate transcription.
Collapse
Affiliation(s)
- X F Zhao
- Departments of Pediatrics and Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | | |
Collapse
|
14
|
Goldfarb AN, Lewandowska K, Pennell CA. Identification of a highly conserved module in E proteins required for in vivo helix-loop-helix dimerization. J Biol Chem 1998; 273:2866-73. [PMID: 9446597 DOI: 10.1074/jbc.273.5.2866] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Basic helix-loop-helix (bHLH) transcription factors often function as heterodimeric complexes consisting of a tissue-specific factor such as SCL/tal or MyoD bound to a broadly expressed E protein. bHLH dimerization therefore appears to represent a key regulatory step in cell lineage determination and oncogenesis. Previous functional and structural studies have indicated that the well defined HLH domain is both necessary and sufficient for dimerization. Most of these studies, however, have employed in vitro systems for analysis of HLH dimerization, and their implications for the requirements for in vivo dimerization remain unclear. Using multiple approaches, we have analyzed bHLH dimerization in intact, living cells and have identified a novel domain in E proteins, domain C, which is required for in vivo dimerization. Domain C, which lies just carboxyl-terminal to helix 2 of the HLH domain, represents the most highly conserved region within E proteins and appears to influence the in vivo conformation of the adjacent HLH domain. These results suggest that HLH dimerization in vivo may represent a complex, regulated process that is distinct from HLH dimerization in vitro.
Collapse
Affiliation(s)
- A N Goldfarb
- Institute of Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4943, USA.
| | | | | |
Collapse
|
15
|
Langlands K, Yin X, Anand G, Prochownik EV. Differential interactions of Id proteins with basic-helix-loop-helix transcription factors. J Biol Chem 1997; 272:19785-93. [PMID: 9242638 DOI: 10.1074/jbc.272.32.19785] [Citation(s) in RCA: 181] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Dimerization of three Id proteins (Id1, Id2, and Id3) with the four class A E proteins (E12, E47, E2-2, and HEB) and two groups of class B proteins, the myogenic regulatory factors (MRFs: MyoD, myogenin, Myf-5 and MRF4/Myf-6), and the hematopoietic factors (Scl/Tal-1, Tal-2, and Lyl-1) were tested in a quantitative yeast 2-hybrid assay. All three Ids bound with high affinity to E proteins, but a much broader range of interactions was observed between Ids and the class B factors. Id1 and Id2 interacted strongly with MyoD and Myf-5 and weakly with myogenin and MRF4/Myf-6, whereas Id3 interacted weakly with all four MRFs. Similar specificities were observed in co-immunoprecipitation and mammalian 2-hybrid analyses. No interactions were found between the Ids and any of the hematopoietic factors. Each Id was able to disrupt the ability of E protein-MyoD complexes to transactivate from a muscle creatine kinase reporter construct in vivo. Finally, mutagenesis experiments showed that the differences between Id1 and Id3 binding map to three amino acids in the first helix and to a small cluster of upstream residues. The Id proteins thus display a signature range of interactions with all of their potential dimerization partners and may play a role in myogenesis which is distinct from that in hematopoiesis.
Collapse
Affiliation(s)
- K Langlands
- Section of Hematology/Oncology, Children's Hospital of Pittsburgh, The, Pittsburgh, Pennsylvania 15213, USA
| | | | | | | |
Collapse
|
16
|
Kast P, Hilvert D. 3D structural information as a guide to protein engineering using genetic selection. Curr Opin Struct Biol 1997; 7:470-9. [PMID: 9266167 DOI: 10.1016/s0959-440x(97)80109-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A great variety of protein systems have been investigated in the past year using structure-guided evolutionary strategies. On the basis of available 3D structural information, critical regions of proteins have been targeted for randomizing mutagenesis and active variants of the corresponding genes have been selected. These approaches help characterize structural and mechanistic features of proteins and have important implications for design.
Collapse
Affiliation(s)
- P Kast
- Department of Molecular Biology, Scripps Research Institute, La Jolla, CA 92037, USA.
| | | |
Collapse
|
17
|
Abstract
The theory of mass transport coupled to macromolecular interactions under chemical kinetic control forms the basis of four different models of the electrophoretic mobility-shift assay of complexes formed between dimerizing proteins and DNA. The theory of mass action was applied to the set of simultaneous dimerization (either simple or ligand-induced) and DNA-binding reactions in order to fix the initial equilibrium composition of mixtures to be assayed. Theoretical mobility-shift patterns were obtained for a range of protein concentrations at constant DNA concentration by numerical solution of the set of simultaneous transport-reaction equations appropriate for each model. In those cases in which dimerization in solution is modeled (including heterodimerization), analysis of the peaks in the patterns provides apparent binding constants, which, when extrapolated to infinite dilution of protein, yield acceptable estimates of equilibrium constants. Those for binding of dimer are products of two or three equilibrium constants, from which the equilibrium binding constant can be extracted, provided that dimerization and, where required, ligand-binding constants are determined by independent physicochemical methods. Dimerization of protein when bound to DNA is distinctive in that extrapolation to infinite dilution of protein is not required.
Collapse
Affiliation(s)
- J R Cann
- Department of Biochemistry/Biophysics/Genetics, University of Colorado Health Sciences Center, Denver 80262, USA
| |
Collapse
|
18
|
Aplan PD, Jones CA, Chervinsky DS, Zhao X, Ellsworth M, Wu C, McGuire EA, Gross KW. An scl gene product lacking the transactivation domain induces bony abnormalities and cooperates with LMO1 to generate T-cell malignancies in transgenic mice. EMBO J 1997; 16:2408-19. [PMID: 9171354 PMCID: PMC1169841 DOI: 10.1093/emboj/16.9.2408] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The product of the scl (also called tal-1 or TCL5) gene is a basic domain, helix-loop-helix (bHLH) transcription factor required for the development of hematopoietic cells. Additionally, scl gene disruption and dysregulation, by either chromosomal translocations or a site-specific interstitial deletion whereby 5' regulatory elements of the sil gene become juxtaposed to the body of the scl gene, is associated with T-cell acute lymphoblastic leukemia (ALL) and T-cell lymphoblastic lymphoma. Here we show that an inappropriately expressed scl protein, driven by sil regulatory elements, can cause aggressive T-cell malignancies in collaboration with a misexpressed LMO1 protein, thus recapitulating the situation seen in a subset of human T-cell ALL. Moreover, we show that inappropriately expressed scl can interfere with the development of other tissues derived from mesoderm. Lastly, we show that an scl construct lacking the scl transactivation domain collaborates with misexpressed LMO1, demonstrating that the scl transactivation domain is dispensable for oncogenesis, and supporting the hypothesis that the scl gene product exerts its oncogenic action through a dominant-negative mechanism.
Collapse
Affiliation(s)
- P D Aplan
- Department of Pediatrics, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Deed RW, Jasiok M, Norton JD. Attenuated function of a variant form of the helix-loop-helix protein, Id-3, generated by an alternative splicing mechanism. FEBS Lett 1996; 393:113-6. [PMID: 8804437 DOI: 10.1016/0014-5793(96)00868-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The Id family of helix-loop-helix proteins function as negative regulators of DNA binding, basic helix-loop-helix proteins in the regulation of cell growth and differentiation. We report here on the identification of a 17 kDa variant of the 14 kDa Id-3 protein termed Id-3L (long version) which possesses a unique 60 amino acid carboxy-terminus generated by read through of a 'coding intron' and alternative splicing. Northern analysis revealed expression of a minor 1.1 kb Id-3L transcript together with the predominant 0.95 kb Id-3 transcript in the majority of adult human tissues analysed. The variant Id-3L protein is functionally distinguishable from conventional Id-3 since in in vitro DNA mobility shift assays, it was greatly impaired in its ability to abrogate binding of the basic helix-loop-helix protein, E47, to an E box recognition sequence.
Collapse
Affiliation(s)
- R W Deed
- CRC Department of Gene Regulation, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, UK.
| | | | | |
Collapse
|