In eukaryotes, chromatin is organized in two types of domains, namely euchromatin and heterochromatin.Euchromatic domains define transcriptionally active portions of the genome, whereas heterochromatin is largely inactive for gene expression.Because heterochromatin formed in one part of the genome may propagate along the chromosome, borders are accordingly established between these distinct regions.A prevailing view of the borders is that they are specific DNA elements that actively inhibit communication between distinct regions on chromosomes, insulation a gene in euchromatin from the influence of its adjacent silencing chromatin.We call these DNA elements as insulatorsi or i boundary elements Another mechanism, some chromatin boundaries do not indeed require barrier proteins recruited by specific DNA elements at the chromosomal borders.Instead, the borders are defined by a balance of opposing enzymatic activities (e.g.acetylation and deacetylation, or acetylation and methylation, of lysine tail on a histone) located at the opposite sides of the resultant borders.In both cases, the barriers proteins which constitute a fixed border or enzymatic proteins which form the apparent gradient of chromatin modification play roles as boundary regulators.