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Sequence-specific DNA binding by AT-hook motifs in MeCP2.

ABSTRACT: MeCP2 is a chromatin-associated protein that is mutated in Rett syndrome. Its methyl-CpG-binding domain interacts with DNA containing methylated cytosine, but other modes of recruitment to the genome have also been proposed. Here, we use in vitro and in vivo assays to investigate the DNA binding specificity of two AT-hook motifs in MeCP2. One exhibits robust sequence-specific DNA binding, whereas the other is a much weaker AT-hook. Our data indicate that these motifs are secondary contributors to DNA binding by MeCP2, and this view is supported by the absence of disease-causing missense mutations at these sites.

SUBMITTER: Lyst MJ

PROVIDER: S-EPMC5028900 | biostudies-other | 2016 Sep

REPOSITORIES: biostudies-other

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Sequence-specific DNA binding by AT-hook motifs in MeCP2.

Lyst Matthew J MJ Connelly John J Merusi Cara C Bird Adrian A

FEBS letters 20160809 17

MeCP2 is a chromatin-associated protein that is mutated in Rett syndrome. Its methyl-CpG-binding domain interacts with DNA containing methylated cytosine, but other modes of recruitment to the genome have also been proposed. Here, we use in vitro and in vivo assays to investigate the DNA binding specificity of two AT-hook motifs in MeCP2. One exhibits robust sequence-specific DNA binding, whereas the other is a much weaker AT-hook. Our data indicate that these motifs are secondary contributors t ...[more]

PMID: 27461740

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Project description:Methyl-CpG binding protein 2 (MeCP2) is a multifunctional protein that guides neuronal development through its binding to DNA, recognition of sites of methyl-CpG (mCpG) DNA modification, and interaction with other regulatory proteins. Our study explores the relationship between mCpG and hydroxymethyl-CpG (hmCpG) recognition mediated by its mCpG binding domain (MBD) and binding cooperativity mediated by its C-terminal polypeptide. Previous study of the isolated MBD of MeCP2 documented an unusual mechanism by which ion uptake is required for discrimination of mCpG and hmCpG from CpG. MeCP2 binding cooperativity suppresses discrimination of modified DNA and is highly sensitive to both the total ion concentration and the type of counterions. Higher than physiological total ion concentrations completely suppress MeCP2 binding cooperativity, indicating a dominant electrostatic component to the interaction. Substitution of SO4(2-) for Cl(-) at physiological total ion concentrations also suppresses MeCP2 binding cooperativity, This effect is of particular note as the intracellular Cl(-) concentration changes during neuronal development. A related effect is that the protein-stabilizing solutes, TMAO and glutamate, reduce MeCP2 (but not isolated MBD) binding affinity by 2 orders of magnitude without affecting the apparent binding cooperativity. These observations suggest that polypeptide flexibility facilitates DNA binding by MeCP2. Consistent with this view, nuclear magnetic resonance (NMR) analyses show that ions have discrete effects on the structure of MeCP2, both MBD and the C-terminal domains. Notably, anion substitution results in changes in the NMR chemical shifts of residues, including some whose mutation causes the autism spectrum disorder Rett syndrome. Binding cooperativity makes MeCP2 an effective competitor with histone H1 for accessible DNA sites. The relationship between MeCP2 binding specificity and cooperativity is discussed in the context of chromatin binding, neuronal function, and neuronal development.

Dataset Information

Sequence-specific DNA binding by AT-hook motifs in MeCP2.

Publications

Sequence-specific DNA binding by AT-hook motifs in MeCP2.

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