OUT, a Novel Basic Helix-Loop-Helix Transcription Factor with an Id-like Inhibitory Activity

Narumi, Osamu; Mori, Seiichi; Boku, Shuken; Tsuji, Yoshihito; Hashimoto, Nobuo; Nishikawa, Shin‐Ichi; Yokota, Yoshifumi

doi:10.1074/jbc.275.5.3510

Cited by 33 publications

(35 citation statements)

References 90 publications

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“…As shown in Fig. 5C, the wild-type GFP-Id2 protein repressed the MyoD-E47-induced transactivation in a dose-dependent manner (lanes 7-10), as reported in our previous study using the untagged Id2 construct (26). Given that GFP-Id2 is able to shuttle between the nucleus and the cytoplasm, its repression activity is not surprising.…”

Section: Decreased Nuclear Export Of Id2 Augments Repression Of E-boxsupporting

confidence: 51%

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Nucleo-cytoplasmic Shuttling of Id2, a Negative Regulator of Basic Helix-Loop-Helix Transcription Factors

Kurooka

Yokota

2005

Journal of Biological Chemistry

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Id proteins function as negative regulators for basic helix-loop-helix transcriptional factors that play important roles in cell fate determination. They preferentially associate with ubiquitously expressed E proteins of the basic helix-loop-helix family and prevent them from binding to DNA and activating transcription. Although their small size suggests that Id proteins enter and exit the nucleus by passive diffusion, several studies have indicated that other pathways may regulate their subcellular localization. In this study, we obtained evidence that Id2 has the ability to shuttle between the nucleus and the cytoplasm. When passive diffusion was prevented by fusion with green fluorescent protein (GFP), Id2 was predominantly localized in the cytoplasm. Using GFP fusion constructs, we demonstrated that the C-terminal region is required for cytoplasmic localization. Nuclear accumulation of GFP-Id2 in cells treated with the nuclear export inhibitor leptomycin B suggests that the nuclear export receptor chromosome region maintenance protein 1 mediates the cytoplasmic localization of Id2. Id2 contains two putative leucine-rich nuclear export signals, and the nuclear export signal in the Cterminal region is essential for nuclear export. On the other hand, the helix-loop-helix domain is important for nuclear localization. Finally, experiments using reporter assays revealed an inverse correlation between nuclear export and transcriptional repression via the E-box sequence. Based on all these findings, we propose that nucleo-cytoplasmic shuttling is a novel mechanism for the regulation of Id2 function.

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Section: Decreased Nuclear Export Of Id2 Augments Repression Of E-boxsupporting

confidence: 51%

“…pE7-TK-luc is a thymidine kinase (TK) firefly luciferase reporter plasmid harboring seven copies of the E-box sequence and is a derivative of pE7-␤A-luc (25). pCMV-MyoD was mentioned in our previous study (26).…”

Section: Methodsmentioning

confidence: 99%

Nucleo-cytoplasmic Shuttling of Id2, a Negative Regulator of Basic Helix-Loop-Helix Transcription Factors

Kurooka

Yokota

2005

Journal of Biological Chemistry

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“…Other examples include some members of the bHLH (47,48), leucine zipper (49), and homeodomain (50) protein families. The way in which the function of Id proteins is integrated at the level of the subnuclear architecture as shown in the present study may also be relevant to these other transcription factor antagonists, in providing a general mechanism through which they can overcome the high DNA-binding free energy of their target proteins.…”

Section: Discussionmentioning

confidence: 99%

Id Proteins Negatively Regulate Basic Helix-Loop-Helix Transcription Factor Function by Disrupting Subnuclear Compartmentalization

O’Toole

Inoue

Emerson

et al. 2003

Journal of Biological Chemistry

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Id helix-loop-helix (HLH) proteins act as global regulators of metazoan cell fate, cell growth, and differentiation. They heterodimerize with and inhibit the DNA-binding function of members of the basic helixloop-helix (bHLH) family of transcription factors. Using real time fluorescence microscopy techniques in single living cells, we show here that nuclear pools of chromatin-associated bHLH transcription factor are freely exchangeable and in constant flux. The existence of a dynamic equilibrium between DNA-bound and free bHLH protein is also directly demonstrable in vitro. By contrast, Id protein is not associated with any subcellular, macromolecular structures and displays a more highly mobile, diffuse nuclear-cytoplasmic distribution. When co-expressed with antagonist Id protein, the chromatinassociated sublocalization of bHLH protein is abolished, and there is an accompanying 100-fold increase in its nuclear mobility to a level expected for freely diffusible Id-bHLH heterodimer. These results suggest that nuclear Id protein acts by sequestering pools of transiently diffusing bHLH protein to prevent reassociation with chromatin domains. Such a mechanism would explain how Id proteins are able to overcome the large DNAbinding free energy of bHLH proteins that is necessary to accomplish their inhibitory effect.Id proteins function as global regulators of cell fate determination. They play a pivotal role in the coordinate regulation of gene expression during cell growth/cell cycle control, differentiation, and tumorigenesis (reviewed in Refs. 1 and 2). Recent studies have also highlighted their role in cellular senescence (3, 4) and in cell fate decisions in cells of specialized lineages such as lymphocytes (5) (reviewed in Ref. 6), vascular endothelial cells (7,8), and neuronal cells (7, 9). The four members of the Id protein family (Id1-Id4) function by directly associating with and modulating the activity of several families of transcriptional regulators (1, 10 -12). However, compelling biochemical and genetic data implicate members of the ubiquitously expressed Class A, basic helix-loop-helix (bHLH) 1 family of "E proteins" as the most important heterodimerization targets for Id proteins in the coordinate regulation of gene expression during cell fate determination (1, 2, 13, 14). In mammals, there are three E protein family genes, E2A (encoding three alternatively spliced variants, E12, E47, and E2-5), E2-2 (ITF2), and HEB (14). The E proteins bind to a consensus "E-box" recognition sequence, present in the transcriptional control regions of numerous cellular genes, either as a homodimer or, more commonly, as a heterodimeric partner with a member of the much larger family of tissue-specific, Class B bHLH proteins. Id proteins lack a basic, DNA-binding domain, and they heterodimerize avidly (via their HLH domain) with bHLH E proteins (13) to prevent the latter from binding to DNA (1,14). Since E proteins are obligate heterodimerization partners for tissue-specific bHLH proteins, this provides a common mechani...

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“…Reduction of heterodimer formation between MyoD and E proteins (including E12 and E47) (Massari and Murre, 2000) has been implicated as a mechanism by which various transcription factors inhibit the capacity of MyoD to activate transcription (Narumi et al, 2000;Sun et al, 2001). We therefore tested if Gli1 reduces heterodimer formation between MyoD and E proteins.…”

Section: Gli1 Reduces Myod and E Protein Heterodimer Formationmentioning

confidence: 99%

The hedgehog regulated oncogenes Gli1 and Gli2 block myoblast differentiation by inhibiting MyoD-mediated transcriptional activation

et al. 2006

Oncogene

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OUT, a Novel Basic Helix-Loop-Helix Transcription Factor with an Id-like Inhibitory Activity

Cited by 33 publications

References 90 publications

Nucleo-cytoplasmic Shuttling of Id2, a Negative Regulator of Basic Helix-Loop-Helix Transcription Factors

Nucleo-cytoplasmic Shuttling of Id2, a Negative Regulator of Basic Helix-Loop-Helix Transcription Factors

Id Proteins Negatively Regulate Basic Helix-Loop-Helix Transcription Factor Function by Disrupting Subnuclear Compartmentalization

The hedgehog regulated oncogenes Gli1 and Gli2 block myoblast differentiation by inhibiting MyoD-mediated transcriptional activation

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