Dynamics of MBD2 deposition across methylated DNA regions during malignant transformation of human mammary epithelial cells (2)

DNA methylation is thought to induce a transcriptional silencing through the combination of two mechanisms: the repulsion of transcriptional activators that do not recognize their binding sites when methylated, and the recruitment of transcriptional repressors that specifically bind methylated DNA. Methyl CpG Binding Domain proteins MeCP2, MBD1 and MBD2 belong to the latter category. However, the exact contribution of each protein in the DNA methylation dependent transcriptional repression occurring during development and diseases remains elusive. Here we present MBD2 ChIPseq data generated from the endogenous protein in an isogenic cellular model of human mammary oncogenic transformation. In immortalized or transformed cells, MBD2 was found in one fourth of methylated regions and associated with transcriptional silencing. Depletion of MBD2 induces upregulations of genes bound by MBD2 and methylated in their transcriptional start site regions. MBD2 was partially redistributed on methylated DNA during oncogenic transformation, independently of DNA methylation changes. Genes downregulated during this transformation preferentially gained MBD2 binding sites on their promoter. Depletion of MBD2 in transformed cells induced the upregulation of some of these repressed genes, independently of the strategy used for the abrogation of oncosuppressive barriers. Our data confirm that MBD2 is a major interpret of DNA methylation, and show an unreported dynamic in this interpretation during oncogenic transformation. Overall design: RNAseq of untreated HMEC-hTERT cells, siCtrl, siMBD2 or DAC treated HMLER cells, siCtrl or siMBD2 treated HME-ZEB1-RAS and HME-shP53-RAS cells, in duplicates.

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Devailly G, Grandin M, Perriaud L, Mathot P, Delcros JG, Bidet Y, Morel AP, Bignon JY, Puisieux A, Mehlen P, Dante R