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Structure of p300 bound to MEF2 on DNA reveals a mechanism of enhanceosome assembly.

He J, Ye J, Cai Y, Riquelme C, Liu JO, Liu X, Han A, Chen L - Nucleic Acids Res. (2011)

Bottom Line: Using structure-guided mutations and a mammalian two-hybrid assay, we show that all three interfaces contribute to the binding of MEF2 to p300, suggesting that p300 may use one of the three interfaces to interact with MEF2 in different cellular contexts and that one p300 can bind three MEF2:DNA complexes simultaneously.These studies, together with previously characterized TAZ2 complexes bound to different transcription factors, demonstrate the potency and versatility of TAZ2 in protein-protein interactions.Our results also support a model wherein p300 promotes the assembly of a higher-order enhanceosome by simultaneous interactions with multiple DNA-bound transcription factors.

View Article: PubMed Central - PubMed

Affiliation: MOE Key Laboratory for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361005, China.

ABSTRACT
Transcription co-activators CBP and p300 are recruited by sequence-specific transcription factors to specific genomic loci to control gene expression. A highly conserved domain in CBP/p300, the TAZ2 domain, mediates direct interaction with a variety of transcription factors including the myocyte enhancer factor 2 (MEF2). Here we report the crystal structure of a ternary complex of the p300 TAZ2 domain bound to MEF2 on DNA at 2.2Å resolution. The structure reveals three MEF2:DNA complexes binding to different sites of the TAZ2 domain. Using structure-guided mutations and a mammalian two-hybrid assay, we show that all three interfaces contribute to the binding of MEF2 to p300, suggesting that p300 may use one of the three interfaces to interact with MEF2 in different cellular contexts and that one p300 can bind three MEF2:DNA complexes simultaneously. These studies, together with previously characterized TAZ2 complexes bound to different transcription factors, demonstrate the potency and versatility of TAZ2 in protein-protein interactions. Our results also support a model wherein p300 promotes the assembly of a higher-order enhanceosome by simultaneous interactions with multiple DNA-bound transcription factors.

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A hypothetical enhanceosome model. Multiple MEF2 dimers bind to numerous sites in the enhancer/promoter region of a targeted gene. Brown balls represent the nucleosomes. p300 is recruited to one MEF2 dimer:DNA complex to initiate the assembly of the activation complex. Subsequent binding of p300 to other two MEF2 dimer:DNA complexes induces a looping of DNA and the assembly of an enhanceosome.
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Figure 6: A hypothetical enhanceosome model. Multiple MEF2 dimers bind to numerous sites in the enhancer/promoter region of a targeted gene. Brown balls represent the nucleosomes. p300 is recruited to one MEF2 dimer:DNA complex to initiate the assembly of the activation complex. Subsequent binding of p300 to other two MEF2 dimer:DNA complexes induces a looping of DNA and the assembly of an enhanceosome.

Mentions: CBP/p300-mediated enhanceosome assembly has long been hypothesized (19–21). Our structure provides the first example where a p300 domain is directly recruited to DNA by a DNA-bound, sequence-specific transcription factor. A surprising finding is that MEF2 binds the p300 TAZ2 domain at three distinct and non-overlapping surfaces, leading to an assembly of a higher-order enhanceosome structure wherein three DNA-bound MEF2 dimers are ‘attracted’ to different faces of the TAZ2 domain. This has two implications for the transcriptional regulation by p300 and MEF2. First, the TAZ2 domain from one p300 molecule could interact with three MEF2 dimers bound to DNA, thereby promoting the assembly of higher-order structures in the promoter and long-range interactions of DNA-bound MEF2 complexes (Figure 6). Our structure does not impose any spatial constraint between the different MEF2 sites as long as they are well separated so the intervening sequences could be looped out. In fact, the MEF2 binding sites could even come from different chromosomes. In this regard, recent ChIP-on-chip studies reveal that MEF2 bind a much larger number of sites in the genome than previously thought, and that most MEF2-targeted promoters contain multiple MEF2 binding sites that are separated far from each other (often more than several kilobases) (31). Second, as discussed above, the TAZ domain can interact with a variety of other proteins, including different transcription factors. The fact that MEF2 can bind three distinct sites on TAZ2 opens up the possibility that MEF2 may bind one of the three sites in a given promoter context, leaving room for the binding of other transcription factors to the TAZ2 domain. This versatility of p300:MEF2 interaction may facilitate combinatorial control of transcription regulation between MEF2 and other transcription factors. Future studies are needed to further address these questions, for example, by analyzing the effect of mutations at different interfaces on the expression of specific subsets of MEF2-targeted genes.Figure 6.


Structure of p300 bound to MEF2 on DNA reveals a mechanism of enhanceosome assembly.

He J, Ye J, Cai Y, Riquelme C, Liu JO, Liu X, Han A, Chen L - Nucleic Acids Res. (2011)

A hypothetical enhanceosome model. Multiple MEF2 dimers bind to numerous sites in the enhancer/promoter region of a targeted gene. Brown balls represent the nucleosomes. p300 is recruited to one MEF2 dimer:DNA complex to initiate the assembly of the activation complex. Subsequent binding of p300 to other two MEF2 dimer:DNA complexes induces a looping of DNA and the assembly of an enhanceosome.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3105382&req=5

Figure 6: A hypothetical enhanceosome model. Multiple MEF2 dimers bind to numerous sites in the enhancer/promoter region of a targeted gene. Brown balls represent the nucleosomes. p300 is recruited to one MEF2 dimer:DNA complex to initiate the assembly of the activation complex. Subsequent binding of p300 to other two MEF2 dimer:DNA complexes induces a looping of DNA and the assembly of an enhanceosome.
Mentions: CBP/p300-mediated enhanceosome assembly has long been hypothesized (19–21). Our structure provides the first example where a p300 domain is directly recruited to DNA by a DNA-bound, sequence-specific transcription factor. A surprising finding is that MEF2 binds the p300 TAZ2 domain at three distinct and non-overlapping surfaces, leading to an assembly of a higher-order enhanceosome structure wherein three DNA-bound MEF2 dimers are ‘attracted’ to different faces of the TAZ2 domain. This has two implications for the transcriptional regulation by p300 and MEF2. First, the TAZ2 domain from one p300 molecule could interact with three MEF2 dimers bound to DNA, thereby promoting the assembly of higher-order structures in the promoter and long-range interactions of DNA-bound MEF2 complexes (Figure 6). Our structure does not impose any spatial constraint between the different MEF2 sites as long as they are well separated so the intervening sequences could be looped out. In fact, the MEF2 binding sites could even come from different chromosomes. In this regard, recent ChIP-on-chip studies reveal that MEF2 bind a much larger number of sites in the genome than previously thought, and that most MEF2-targeted promoters contain multiple MEF2 binding sites that are separated far from each other (often more than several kilobases) (31). Second, as discussed above, the TAZ domain can interact with a variety of other proteins, including different transcription factors. The fact that MEF2 can bind three distinct sites on TAZ2 opens up the possibility that MEF2 may bind one of the three sites in a given promoter context, leaving room for the binding of other transcription factors to the TAZ2 domain. This versatility of p300:MEF2 interaction may facilitate combinatorial control of transcription regulation between MEF2 and other transcription factors. Future studies are needed to further address these questions, for example, by analyzing the effect of mutations at different interfaces on the expression of specific subsets of MEF2-targeted genes.Figure 6.

Bottom Line: Using structure-guided mutations and a mammalian two-hybrid assay, we show that all three interfaces contribute to the binding of MEF2 to p300, suggesting that p300 may use one of the three interfaces to interact with MEF2 in different cellular contexts and that one p300 can bind three MEF2:DNA complexes simultaneously.These studies, together with previously characterized TAZ2 complexes bound to different transcription factors, demonstrate the potency and versatility of TAZ2 in protein-protein interactions.Our results also support a model wherein p300 promotes the assembly of a higher-order enhanceosome by simultaneous interactions with multiple DNA-bound transcription factors.

View Article: PubMed Central - PubMed

Affiliation: MOE Key Laboratory for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361005, China.

ABSTRACT
Transcription co-activators CBP and p300 are recruited by sequence-specific transcription factors to specific genomic loci to control gene expression. A highly conserved domain in CBP/p300, the TAZ2 domain, mediates direct interaction with a variety of transcription factors including the myocyte enhancer factor 2 (MEF2). Here we report the crystal structure of a ternary complex of the p300 TAZ2 domain bound to MEF2 on DNA at 2.2Å resolution. The structure reveals three MEF2:DNA complexes binding to different sites of the TAZ2 domain. Using structure-guided mutations and a mammalian two-hybrid assay, we show that all three interfaces contribute to the binding of MEF2 to p300, suggesting that p300 may use one of the three interfaces to interact with MEF2 in different cellular contexts and that one p300 can bind three MEF2:DNA complexes simultaneously. These studies, together with previously characterized TAZ2 complexes bound to different transcription factors, demonstrate the potency and versatility of TAZ2 in protein-protein interactions. Our results also support a model wherein p300 promotes the assembly of a higher-order enhanceosome by simultaneous interactions with multiple DNA-bound transcription factors.

Show MeSH
Related in: MedlinePlus