Molecular Context-Dependent Effects Induced by Rett Syndrome-Associated Mutations in MeCP2.

David Ortega-Alarcon,Olga C. Jorge-Torres,Manel Esteller,Adrian Velazquez-Campoy,Rafael Claveria-Gimeno,Olga Abian,Sonia Vega

doi:10.3390/biom10111533

Abstract

Methyl-CpG binding protein 2 (MeCP2) is a transcriptional regulator and a chromatin-binding protein involved in neuronal development and maturation. Loss-of-function mutations in MeCP2 result in Rett syndrome (RTT), a neurodevelopmental disorder that is the main cause of mental retardation in females. MeCP2 is an intrinsically disordered protein (IDP) constituted by six domains. Two domains are the main responsible elements for DNA binding (methyl-CpG binding domain, MBD) and recruitment of gene transcription/silencing machinery (transcription repressor domain, TRD). These two domains concentrate most of the RTT-associated mutations. R106W and R133C are associated with severe and mild RTT phenotype, respectively. We have performed a comprehensive characterization of the structural and functional impact of these substitutions at molecular level. Because we have previously shown that the MBD-flanking disordered domains (N-terminal domain, NTD, and intervening domain, ID) exert a considerable influence on the structural and functional features of the MBD (Claveria-Gimeno, R. et al. Sci Rep. 2017, 7, 41635), here we report the biophysical study of the influence of the protein scaffold on the structural and functional effect induced by these two RTT-associated mutations. These results represent an example of how a given mutation may show different effects (sometimes opposing effects) depending on the molecular context.

Highlights

Methyl-CpG binding protein 2 (MeCP2) is an intrinsically disordered protein (IDP) involved in early stages of neuronal development, differentiation, maturation, and synaptic plasticity control [1]
MeCP2 exhibits a promoter-specific double-stranded DNA (dsDNA) interaction required for finely tuning gene transcription, but it binds massively to heterochromatin when acting as a chromatin architecture remodeling factor
Rett syndrome (RTT)-associated MeCP2 variants were expressed in E. coli and successfully purified by affinity chromatography, allowing us to study the potential destabilizing impact of the selected mutations on the methyl binding domain (MBD) conformation and its interaction with dsDNA

Summary

Introduction

Methyl-CpG binding protein 2 (MeCP2) is an intrinsically disordered protein (IDP) involved in early stages of neuronal development, differentiation, maturation, and synaptic plasticity control [1]. It was identified as a methyl-dependent chromatin binding protein and an epigenetic methylation reader, and, associated to gene silencing, recent evidences suggest it could be considered as a transcriptional regulator whose primary role is recruiting co-repressor complexes to methylated sites and contributing to decreasing transcriptional noise [2]. Duplication of mecp gene results in overexpression of MeCP2 and leads to MeCP2 duplication syndrome (MDS), another much rarer disorder affecting males and, strikingly, sharing phenotypic features with RTT, such as severe intellectual disability and impaired motor function

Objectives

Methods

Results