Molecular Cloning and Characterization of DEC2, a New Member of Basic Helix-Loop-Helix Proteins

Fujimoto, Katsumi; Shen, Ming; Noshiro, Mitsuhide; Matsubara, Kazumi; Shingu, Sohei; Honda, K.; Yoshida, Eri; Suardita, Ketut; Matsuda, Yoichi; Kato, Yukio

doi:10.1006/bbrc.2000.4133

Cited by 92 publications

(116 citation statements)

References 31 publications

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“…1A). The amino acid sequence is identical to the recently reported mouse DEC2 (GenBank TM accession number AB044090) but contains a longer 3Ј-untranslated region (33). Domain analysis (Fig.…”

Section: Cdna Cloning and Expression Analysis Of Msharp-1-tosupporting

confidence: 57%

mSharp-1/DEC2, a Basic Helix-Loop-Helix Protein Functions as a Transcriptional Repressor of E Box Activity and Stra13 Expression

Azmi

Sun

Ozog

et al. 2003

Journal of Biological Chemistry

103

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Transcription factors belonging to the basic helixloop-helix (bHLH) family play critical roles in the regulation of cellular differentiation of distinct cell types. In this study, we have characterized the DNA-binding and transcriptional properties of the bHLH factor mSharp-1/DEC2. mSharp-1 belongs to the Hairy/Enhancer of Split subfamily of bHLH factors and exhibits the highest structural and sequence identity with Stra13. We show that mSharp-1 specifically binds to the E box motif (CANNTG) as a homodimer and acts as a potent transcriptional repressor of MyoD-and E12-induced E box activity and differentiation. The inhibitory activity of mSharp-1 occurs through several mechanisms including occupancy of E box sites by mSharp-1 homodimers and by direct physical interaction with MyoD and E proteins. Furthermore, by using gel mobility shift assays and chromatin immunoprecipitation experiments, we have identified Stra13 as a target for mSharp-1-mediated repression. We demonstrate that transcriptional repression of Stra13 depends, in part, on binding of mSharp-1 to three conserved E box motifs in the Stra13 proximal promoter. Moreover, mSharp-1 directly interacts with the transcriptional activator Sp1 and impairs Sp1 induction of Stra13 promoter. Our results suggest that mSharp-1 functions as a transcriptional repressor by DNA binding dependent and independent mechanisms.Members of the basic helix-loop-helix (bHLH) 1 superfamily of transcription factors are expressed in a wide range of tissues during development and are involved in the regulation of cell fate determination, myogenesis, neurogenesis, and hematopoiesis (1, 2). The common structures shared among the members of this superfamily are the basic domain, which is required for DNA binding, and the helix-loop-helix domain, which is involved in dimerization (3, 4).Based on the dimerization properties, tissue distribution, and the transcriptional activities, bHLH proteins can be categorized into three classes (5). Class A bHLH factors contain the mammalian "E" proteins, which include the two E2A gene products E12 and E47 as well as E2-2 and HEB. E proteins are ubiquitously expressed and can form homodimers or heterodimers with bHLH factors of the same class as well as with other classes. Class B bHLH proteins tend to be expressed in a tissue or cell type-specific manner and function as heterodimers with the class A bHLH factors. bHLH factors involved in tissue-specific differentiation generally belong to the class B subfamily and include the myogenic factors MyoD and myogenin, the neurogenic factors Mash1, NeuroD, and neurogenins, as well as the bHLH proteins SCL/TAL which are important for hematopoiesis (6 -14). Both class A and class B bHLH factors bind to a common DNA sequence called the E box (CANNTG) commonly found in the promoter or enhancer regions of numerous developmentally regulated genes (15) and function as transcriptional activators. Class C bHLH factors (2) contain the Drosophila Hairy and Enhancer of Split [E(Spl)] proteins, the mammalian Hes protei...

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Section: Cdna Cloning and Expression Analysis Of Msharp-1-tosupporting

confidence: 57%

mSharp-1/DEC2, a Basic Helix-Loop-Helix Protein Functions as a Transcriptional Repressor of E Box Activity and Stra13 Expression

Azmi

Sun

Ozog

et al. 2003

Journal of Biological Chemistry

103

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“…bHLH are targets of the Notch signaling pathway (Davis and Turner, 2001;Iso et al, 2003), which can be dysregulated in a variety of human neoplasms (Davis and Turner, 2001;Allenspach et al, 2002). Proteins encoded by the Class B bHLH protein 3 (BHLHB3: also known as DEC2, SHARP-1) gene and its homolog Class B bHLH protein 2 (BHLHB2: also known as DEC1, STRA13, SHARP-2) share 42% total sequence identity and 97% identity in the bHLH region (Fujimoto et al, 2001). Both genes encode bHLH transcriptional repressors involved in the regulation of the mammalian molecular clock (Honma et al, 2002).…”

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confidence: 99%

BHLHB3: a candidate tumor suppressor in lung cancer

et al. 2008

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BHLHB3 is a basic helix-loop-helix (bHLH) domaincontaining protein that acts as a transcriptional repressor. We found that BHLHB3 transcript levels were low in three human lung cancer cell lines and downregulated in human lung adenocarcinomas as compared to normal lung tissue. BHLHB3 gene overexpression inhibited colony formation of A549, NCI-H520 and NCI-H596 lung cancer cells. The reduced colony growth was likely due to inhibition of cell proliferation as suggested by the downregulation of cyclin D1 (CCND1) expression in NCI-H520 cells transfected to overexpress the BHLHB3 gene; no evidence of apoptosis was observed. These results point to the potential role of the BHLHB3 protein as a tumor suppressor for lung cancer.

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“…The HLH domain in the bHLH motif is responsible for dimerization, whereas the basic region mediates DNA binding (1). Based on sequence alignment and domain analysis, human DEC (differentially expressed in chondrocytes), mouse STRA (stimulated with retinoic acid), and rat SHARP (split and hairy related protein) constitute a new and structurally distinct class of bHLH proteins (7)(8)(9)(10). These proteins are distantly related to Drosophila Hairy and E(spl) as well as the mammalian homologues (e.g.…”

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confidence: 99%

“…Like Hairy/E(spl)/Hes, DEC/STRA/SHARPs contain an orange domain and a proline residue in the DNA binding domain. However, the proline is located 2 residues more toward the NH 2 terminus (1,8). Another major structural difference on the functional domains is that DEC/STRA/ SHARPs, unlike Hairy/E(Spl)/Hes proteins, lack the COOHterminal WRPW tetrapeptide motif (13).…”

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confidence: 99%

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DEC1 Negatively Regulates the Expression of DEC2 through Binding to the E-box in the Proximal Promoter

Xie

Song

et al. 2003

Journal of Biological Chemistry

126

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Human DEC (differentially expressed in chondrocytes), mouse STRA (stimulated with retinoic acid), and rat SHARP (split and hairy related protein) proteins constitute a new and structurally distinct class of the basic helix-loop-helix proteins. In each species, two members are identified with a sequence identity of >90% in the basic helix-loop-helix region and ϳ40% in the total proteins, respectively. Recently, we have reported that DEC1 is abundantly expressed in colon carcinomas but not in the adjacent normal tissues. The present study was undertaken to extend the expression study of DEC1 and to determine whether DEC1 and DEC2 had similar expression patterns among paired cancer-normal tissues from the colon, lung, and kidney. Without exceptions, DEC1 was markedly higher in the carcinomas, whereas the opposite was true with DEC2. In stable transfectants, tetracycline-induced expression of DEC1 caused proportional decreases in the expression of DEC2. Co-transfection with DEC1 repressed the activity of a DEC2 promoter reporter by as much as 90%. The repression was observed with wild type DEC1 but not its DNA binding-defective mutants. Studies with deletion and site-directed mutants located, in the proximal promoter, an E-box motif that supported the DEC1-mediated repression. Disruption of this E-box markedly abolished the ability of the reporter to respond to DEC1. Our findings assign for DEC1 the first target gene that is regulated through direct DNA binding. DEC/STRA/ SHARP proteins are highly identical in the DNA binding domain but much more diverse in other areas. DEC1-mediated repression on the expression of DEC2 provides an important mechanism that these transcription factors regulate the cellular function not only by modulating the expression of their target genes but also the expression of members within the same class.The basic helix-loop-helix (bHLH) 1 proteins are intimately associated with developmental events such as cell differentiation and lineage commitment (1-6). The HLH domain in the bHLH motif is responsible for dimerization, whereas the basic region mediates DNA binding (1). Based on sequence alignment and domain analysis, human DEC (differentially expressed in chondrocytes), mouse STRA (stimulated with retinoic acid), and rat SHARP (split and hairy related protein) constitute a new and structurally distinct class of bHLH proteins (7-10). These proteins are distantly related to Drosophila Hairy and E(spl) as well as the mammalian homologues (e.g. HES) with the highest sequence identity (ϳ40%) in the bHLH region (1,11,12). Like Hairy/E(spl)/Hes, DEC/STRA/SHARPs contain an orange domain and a proline residue in the DNA binding domain. However, the proline is located 2 residues more toward the NH 2 terminus (1, 8). Another major structural difference on the functional domains is that DEC/STRA/ SHARPs, unlike Hairy/E(Spl)/Hes proteins, lack the COOHterminal WRPW tetrapeptide motif (13). Through this sequence, Hairy/E(spl)/Hes recruit corepressor Groucho to the transcription regulatory complex (13)....

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Molecular Cloning and Characterization of DEC2, a New Member of Basic Helix-Loop-Helix Proteins

Cited by 92 publications

References 31 publications

mSharp-1/DEC2, a Basic Helix-Loop-Helix Protein Functions as a Transcriptional Repressor of E Box Activity and Stra13 Expression

mSharp-1/DEC2, a Basic Helix-Loop-Helix Protein Functions as a Transcriptional Repressor of E Box Activity and Stra13 Expression

BHLHB3: a candidate tumor suppressor in lung cancer

DEC1 Negatively Regulates the Expression of DEC2 through Binding to the E-box in the Proximal Promoter

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