Establishment of Distinct MyoD, E2A, and Twist DNA Binding Specificities by Different Basic Region-DNA Conformations

Kophengnavong, Thiphaphone; Michnowicz, Jennifer E.; Blackwell, T. Keith

doi:10.1128/mcb.20.1.261-272.2000

Cited by 56 publications

(60 citation statements)

References 63 publications

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“…The Id proteins are HLH factors that lack the basic DNA-binding domain and competitively heterodimerize with E-proteins, preventing DNA binding to an E-box (Benezra et al 1990). In addition, Eproteins can heterodimerize with bHLH transcriptional repressors, such as HES proteins (Dec2) (Azmi et al 2004;Fujimoto et al 2007) or Twist (Kophengnavong et al 2000) or, as in this study, MSC (see also Lu et. al.…”

Section: Discussionmentioning

confidence: 99%

MyoD and E-protein heterodimers switch rhabdomyosarcoma cells from an arrested myoblast phase to a differentiated state

et al. 2009

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Rhabdomyosarcomas are characterized by expression of myogenic specification genes, such as MyoD and/or Myf5, and some muscle structural genes in a population of cells that continues to replicate. Because MyoD is sufficient to induce terminal differentiation in a variety of cell types, we have sought to determine the molecular mechanisms that prevent MyoD activity in human embryonal rhabdomyosarcoma cells. In this study, we show that a combination of inhibitory Musculin:E-protein complexes and a novel splice form of E2A compete with MyoD for the generation of active full-length E-protein:MyoD heterodimers. A forced heterodimer between MyoD and the full-length E12 robustly restores differentiation in rhabdomyosarcoma cells and broadly suppresses multiple inhibitory pathways. Our studies indicate that rhabdomyosarcomas represent an arrested progress through a normal transitional state that is regulated by the relative abundance of heterodimers between MyoD and the full-length E2A proteins. The demonstration that multiple inhibitory mechanisms can be suppressed and myogenic differentiation can be induced in the RD rhabdomyosarcomas by increasing the abundance of MyoD: E-protein heterodimers suggests a central integrating function that can be targeted to force differentiation in muscle cancer cells.[Keywords: E2A; Musculin; MyoD; myogenesis; rhabdomyosarcoma] Supplemental material is available at http://www.genesdev.org.

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Section: Discussionmentioning

confidence: 99%

MyoD and E-protein heterodimers switch rhabdomyosarcoma cells from an arrested myoblast phase to a differentiated state

et al. 2009

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“…2E). 3.3. Binding of wild-type TWIST proteins to a DNA sequence speci¢c of the human TWIST/E12 heterodimers Based on functional data obtained in invertebrates [9,11], and more recently in mouse [23], a putative Twist binding site has been identi¢ed. We therefore designed a double-stranded DNA probe containing an hexanucleotide motif CATATG (NdeI E-box) for assaying the binding capacities of the human protein.…”

Section: Expression Dimer Formation and Intracellular Localisationmentioning

confidence: 99%

Mutations in the basic domain and the loop–helix II junction of TWIST abolish DNA binding in Saethre–Chotzen syndrome

et al. 2001

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Saethre^Chotzen syndrome is an autosomal dominant skull disorder resulting from premature fusion of coronal sutures (craniosynostosis). It is caused by mutations in the TWIST gene encoding a basic Helix^Loop^Helix transcription factor. Here we report on the identification of a novel mutation affecting a highly conserved residue of the basic domain. Unlike nonsense and missense mutations lying within helices, this mutation does not affect protein stability or heterodimerisation of TWIST with its partner E12. However, it does abolish TWIST binding capacity to a target E-box as efficiently as two missense mutations in the loop^helix II junction. By contrast, elongation of the loop through a 7 amino acid insertion appears not to hamper binding to the DNA target. We conclude that loss of TWIST protein function in Saethre^Chotzen patients can occur at three different levels, namely protein stability, dimerisation, and DNA binding and that the loop^helix II junction is essential for effective protein^DNA interaction. ß

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“…They mediate their function through binding to DNA elements of the NCANNTGN consensus sequence termed E-boxes (1,2). The evolutionarily conserved molecular mechanisms leading to DNA binding have been firmly established.…”

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confidence: 99%

Mechanism of Transcriptional Activation by the Proto-oncogene Twist1

Laursen

Mielke

Iannaccone

et al. 2007

Journal of Biological Chemistry

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Mammalian Twist1, a master regulator in development and a key factor in tumorigenesis, is known to repress transcription by several mechanisms and is therefore considered to mediate its function mainly through inhibition. A role of Twist1 as transactivator has also been reported but, so far, without providing a mechanism for such an activity. Here we show that heterodimeric complexes of Twist1 and E12 mediate E-boxdependent transcriptional activation. We identify a novel Twist1 transactivation domain that coactivates together with the less potent E12 transactivation domain. We found three specific residues in the highly conserved WR domain to be essential for the transactivating function of murine Twist1 and suggest an ␣-helical structure of the transactivation domain.When the human genome was sequenced, one of the surprising results was the low number of genes, summing up to only about one-tenth of the expected number. Explanations for this apparent lack of genes were found in differential gene splicing and protein modification as well as in the combinatorial use of regulating signals and transcription factors. A third explanation, multifunctional proteins, has so far received little attention. Here we show that the basic helix-loop-helix (bHLH) 2 protein Twist1, a known transcriptional inhibitor, can also function as an activator, depending on the regulatory sequences of the target genes. Identification of this additional molecular mechanism may aid in explaining the pleiotropic effects of Twist1 in development and in understanding the complex phenotype of the human Saethre-Chotzen syndrome, which is caused by haploid insufficiency of Twist1.Tissue-specifically expressed bHLH transcription factors are important regulators during embryonic development and postnatal life. They mediate their function through binding to DNA elements of the NCANNTGN consensus sequence termed E-boxes (1, 2). The evolutionarily conserved molecular mechanisms leading to DNA binding have been firmly established. In brief, two amphipathic ␣-helices connected by a loop region form the HLH motif, a protein interaction domain through which bHLH factors form homo-or heterodimers. A region of basic residues N-terminal to the HLH motif is necessary for DNA binding. Members of a class of ubiquitously expressed bHLH factors termed E-proteins serve as activating dimerization partners for tissue-specific bHLH factors (3, 4). In general, single E-boxes are sufficient for bHLH responsiveness, yet cooperative binding to dual E-boxes has been observed (5). Id proteins constitute a specific class of inhibitory HLH factors, which are unable to bind DNA due to a lack of basic regions (6). The Id proteins consequently function as negative regulators.Although dimerization and DNA binding are mechanistically similar for all bHLH proteins, the transactivational mechanisms are often of different evolutionary origin. The closely related myogenic bHLH factors Myf5 and MyoD1 both up-regulate muscle-specific genes such as muscle creatine kinase, yet the sequence...

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Establishment of Distinct MyoD, E2A, and Twist DNA Binding Specificities by Different Basic Region-DNA Conformations

Cited by 56 publications

References 63 publications

MyoD and E-protein heterodimers switch rhabdomyosarcoma cells from an arrested myoblast phase to a differentiated state

MyoD and E-protein heterodimers switch rhabdomyosarcoma cells from an arrested myoblast phase to a differentiated state

Mutations in the basic domain and the loop–helix II junction of TWIST abolish DNA binding in Saethre–Chotzen syndrome

Mechanism of Transcriptional Activation by the Proto-oncogene Twist1

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