FIGURE 1.

Schematic illustration of region-specific DNA methylation manipulations using the CRISPR system. Cells are co-transfected with a plasmid for expression of dCas9-DNMT3A-3L and the sgRNA expression plasmids. The dCas9 fusion protein is guided to a specific region of the genome by the sgRNAs where it brings DNMT3A-3L close to the DNA, resulting in site-specific methylation. As the transfection is transient, after several cell divisions, the fusion protein expression is lost but the DNA methylation pattern is maintained by the endogenous DNMT1 during genomic DNA replication. A similar method involving the dCas9-TET1 fusion enabled site-specific demethylation of DNA. The yellow spheres indicate methylated CpG.