HP1 is involved in regulating the global impact of DNA methylation on alternative splicing

The global impact of DNA methylation on alternative splicing is largely unknown. Using a genome-wide approach in wild-type and methylation-deficient embryonic stem cells, we found that DNA methylation can act both as an enhancer and as a silencer of splicing, and affects the splicing of more than 20% of alternative exons. These exons are characterized by distinct genetic and epigenetic signatures. Alternative splicing regulation of a subset of these exons can be explained by Heterochromatin protein 1 (HP1), which silences or enhances exon recognition in a position-dependent manner. We constructed an experimental system using site-specific targeting of a methylated/unmethylated gene, and demonstrate a direct causal relationship between DNA methylation and alternative splicing. HP1 regulates this gene’s alternative splicing in a methylation-dependent manner by recruiting splicing factors to its methylated form. Our results demonstrate DNA methylation''s significant global influence on mRNA splicing, and identify a specific mechanism of splicing regulation mediated by HP1. Overall design: BS-seq on WT mouse ES cells (2 replicates), MNase-seq on WT and TKO cells (3 replicates), mRNA-seq on WT and TKO cells as well as HP1 knock-down cells (2 replicates for each sample)

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Yearim A, Gelfman S, Shayevitch R, Melcer S, Glaich O, Mallm JP, Nissim-Rafinia M, Cohen AH, Rippe K, Meshorer E, Ast G