Enhancer requirement for histone methylation linked with gene activation.

Enhancers cause a high level of transcription and activation of chromatin structure at target genes. Hyperacetylation of histones H3 and H4, a mark of active chromatin, is established broadly across target loci by enhancers that function over long distances. In the present study, we studied the role of an enhancer in methylation of various lysine residues on H3 by comparing a model gene locus having an active enhancer with one in which the enhancer has been inactivated within the context of minichromosomes. The intact enhancer affected histone methylation at K4, K9 and K36 in distinct ways depending on the methylation level and the location in the locus. All three lysine residues were highly tri-methylated in the coding region of the gene linked to the active enhancer but not the inactive enhancer. However di-methylation of K9 and K36 was not affected by the enhancer. The enhancer region itself was marked by mono-methylation at K4 and K9, distinguishing it from the methyl marks in the gene coding region. These results indicate that an enhancer has roles in establishing active histone methylation patterns linked with gene transcription rather than removing methylation linked with gene inactivation.