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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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Protein–protein interactions at Interface I. (A) Structural comparison of Interface I (p300 in green and MEF2 in gold) with the Cabin1:MEF2:DNA complex (red) and the HDAC9:MEF2:DNA complex (cyan). The structures are superimposed by the Cα backbone of the β strands of the MEF2 core. (B) View from the side of helix α4 of the p300 TAZ2 domain. Interacting residues are shown in stick model. Throughout the illustrations, residues from p300 are italicized and labeled with black fonts while residues from MEF2 are labeled according to the protein color. (C) View from the C-terminal end of helix α4.
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Figure 3: Protein–protein interactions at Interface I. (A) Structural comparison of Interface I (p300 in green and MEF2 in gold) with the Cabin1:MEF2:DNA complex (red) and the HDAC9:MEF2:DNA complex (cyan). The structures are superimposed by the Cα backbone of the β strands of the MEF2 core. (B) View from the side of helix α4 of the p300 TAZ2 domain. Interacting residues are shown in stick model. Throughout the illustrations, residues from p300 are italicized and labeled with black fonts while residues from MEF2 are labeled according to the protein color. (C) View from the C-terminal end of helix α4.

Mentions: Interface I is formed between helix α4 of the TAZ2 domain and one of the MEF2 dimers. Here helix α4 of the TAZ2 domain packs diagonally between helices H2 of the MEF2 dimer. This arrangement is very similar to the binding of the amphipathic helix of Cabin1 and HDAC9 to MEF2, however, the exact positions of the helices are slightly different in different complexes (Figure 3A). Previously we showed that the binding of Cabin1 and HDAC9 to MEF2 induced a shift of helix H2 and conformational changes of the L2 loop between helix H2 and strand S3 (53,57,58). The L2 conformations of MEF2 bound to the p300 TAZ2 domain are indeed notably different from that seen in the Cabin1:MEF2 and HDAC9:MEF2 complexes (Figure 3A). The detailed interactions of IF-I share many features observed at the Cabin1:MEF2 and HDAC9:MEF2 interfaces (Figure 3B and C). Leu1818 and Leu1822 of p300 bind the hydrophobic groove of MEF2 similarly to homologous leucine residues in Cabin1 and HDAC9 (residues of p300 are italicized throughout the text) (57,58). Surrounding the hydrophobic interactions are numerous salt bridges and hydrogen bond networks. At the N-terminal end of TAZ2 α4, Arg1814 engages in electrostatic interactions with Asp61 and Asp63 of MEF2, whereas Gln1811and Gln1815 form hydrogen bonds with Asp63 and the main chain carbonyl of Thr70 of MEF2, respectively. Both Gln1811and Gln1815 are also in van der Waals contact with Tyr69 of MEF2. At the C-terminal end of TAZ2 α4, Arg1829 engages in electrostatic interactions with Asp61 and Asp63 of the other MEF2 monomer. Along the helix of TAZ2 α4, the long aliphatic side chains of Arg1814, Gln1815, Gln1819 and Arg1821 make extensive van der Waals contacts with residues of helix H2 of the MEF2 dimer. Here, Gln1819 also forms a hydrogen bond with Thr70 while Arg1821 forms a salt bridge with Glu71. Overall, IF-I shows a remarkably similar binding mode to Cabin1 and HDAC9 as well as new features of protein–protein interactions.Figure 3.


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)

Protein–protein interactions at Interface I. (A) Structural comparison of Interface I (p300 in green and MEF2 in gold) with the Cabin1:MEF2:DNA complex (red) and the HDAC9:MEF2:DNA complex (cyan). The structures are superimposed by the Cα backbone of the β strands of the MEF2 core. (B) View from the side of helix α4 of the p300 TAZ2 domain. Interacting residues are shown in stick model. Throughout the illustrations, residues from p300 are italicized and labeled with black fonts while residues from MEF2 are labeled according to the protein color. (C) View from the C-terminal end of helix α4.
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Figure 3: Protein–protein interactions at Interface I. (A) Structural comparison of Interface I (p300 in green and MEF2 in gold) with the Cabin1:MEF2:DNA complex (red) and the HDAC9:MEF2:DNA complex (cyan). The structures are superimposed by the Cα backbone of the β strands of the MEF2 core. (B) View from the side of helix α4 of the p300 TAZ2 domain. Interacting residues are shown in stick model. Throughout the illustrations, residues from p300 are italicized and labeled with black fonts while residues from MEF2 are labeled according to the protein color. (C) View from the C-terminal end of helix α4.
Mentions: Interface I is formed between helix α4 of the TAZ2 domain and one of the MEF2 dimers. Here helix α4 of the TAZ2 domain packs diagonally between helices H2 of the MEF2 dimer. This arrangement is very similar to the binding of the amphipathic helix of Cabin1 and HDAC9 to MEF2, however, the exact positions of the helices are slightly different in different complexes (Figure 3A). Previously we showed that the binding of Cabin1 and HDAC9 to MEF2 induced a shift of helix H2 and conformational changes of the L2 loop between helix H2 and strand S3 (53,57,58). The L2 conformations of MEF2 bound to the p300 TAZ2 domain are indeed notably different from that seen in the Cabin1:MEF2 and HDAC9:MEF2 complexes (Figure 3A). The detailed interactions of IF-I share many features observed at the Cabin1:MEF2 and HDAC9:MEF2 interfaces (Figure 3B and C). Leu1818 and Leu1822 of p300 bind the hydrophobic groove of MEF2 similarly to homologous leucine residues in Cabin1 and HDAC9 (residues of p300 are italicized throughout the text) (57,58). Surrounding the hydrophobic interactions are numerous salt bridges and hydrogen bond networks. At the N-terminal end of TAZ2 α4, Arg1814 engages in electrostatic interactions with Asp61 and Asp63 of MEF2, whereas Gln1811and Gln1815 form hydrogen bonds with Asp63 and the main chain carbonyl of Thr70 of MEF2, respectively. Both Gln1811and Gln1815 are also in van der Waals contact with Tyr69 of MEF2. At the C-terminal end of TAZ2 α4, Arg1829 engages in electrostatic interactions with Asp61 and Asp63 of the other MEF2 monomer. Along the helix of TAZ2 α4, the long aliphatic side chains of Arg1814, Gln1815, Gln1819 and Arg1821 make extensive van der Waals contacts with residues of helix H2 of the MEF2 dimer. Here, Gln1819 also forms a hydrogen bond with Thr70 while Arg1821 forms a salt bridge with Glu71. Overall, IF-I shows a remarkably similar binding mode to Cabin1 and HDAC9 as well as new features of protein–protein interactions.Figure 3.

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