Abstract
ASC-2 is a recently isolated transcriptional cointegrator molecule, which is amplified in human cancers and stimulates transactivation by nuclear receptors, AP-1, nuclear factor kappaB (NFkappaB), serum response factor (SRF), and numerous other transcription factors. ASC-2 contained two nuclear receptor-interaction domains, both of which are dependent on the integrity of their core LXXLL sequences. Surprisingly, the C-terminal LXXLL motif specifically interacted with oxysterol receptor LXRss, whereas the N-terminal motif bound a broad range of nuclear receptors. These interactions appeared to be essential because a specific subregion of ASC-2 including the N- or C-terminal LXXLL motif acted as a potent dominant negative mutant with transactivation by appropriate nuclear receptors. In addition, the autonomous transactivation domain (AD) of ASC-2 was found to consist of three separable subregions; i.e. AD1, AD2, and AD3. In particular, AD2 and AD3 were binding sites for CREB binding protein (CBP), and CBP-neutralizing E1A repressed the autonomous transactivation function of ASC-2. Furthermore, the receptor transactivation was not enhanced by ASC-2 in the presence of E1A and significantly impaired by overexpressed AD2. From these results, we concluded that ASC-2 directly binds to nuclear receptors and recruits CBP to mediate the nuclear receptor transactivation in vivo.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Binding Sites
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CREB-Binding Protein
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Cell Line
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Escherichia coli
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Gene Expression
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Glutathione Transferase / genetics
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HeLa Cells
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Humans
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Intracellular Signaling Peptides and Proteins*
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Mice
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Nuclear Proteins / chemistry
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Nuclear Proteins / metabolism
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Nuclear Proteins / pharmacology*
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Nuclear Receptor Coactivators
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Peptide Fragments / chemistry
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Peptide Fragments / metabolism
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Plasmids / genetics
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Polymerase Chain Reaction
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Protein Structure, Secondary
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Receptors, Cytoplasmic and Nuclear / metabolism*
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Receptors, Steroid / metabolism
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Receptors, Thyroid Hormone / chemistry
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Receptors, Thyroid Hormone / metabolism
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae / enzymology
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Structure-Activity Relationship
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Trans-Activators / chemistry
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Trans-Activators / metabolism
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Trans-Activators / pharmacology*
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Transcription Factors / chemistry*
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Transcription Factors / genetics
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Transcription Factors / physiology*
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Transcriptional Activation*
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Transfection
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beta-Galactosidase / genetics
Substances
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Intracellular Signaling Peptides and Proteins
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NCOA6 protein, human
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Ncoa6 protein, mouse
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Nuclear Proteins
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Nuclear Receptor Coactivators
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Peptide Fragments
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Receptors, Cytoplasmic and Nuclear
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Receptors, Steroid
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Receptors, Thyroid Hormone
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Recombinant Fusion Proteins
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Trans-Activators
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Transcription Factors
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oxysterol binding protein
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CREB-Binding Protein
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CREBBP protein, human
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Crebbp protein, mouse
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Glutathione Transferase
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beta-Galactosidase