Histone H4-lysine 20 monomethylation is increased in promoter and coding regions of active genes and correlates with hyperacetylation

Abstract

Methylation and acetylation of position-specific lysine residues in the N-terminal tail of histones H3 and H4 play an important role in regulating chromatin structure and function. In the case of H3-Lys4, H3-Lys 9, H3-Lys27, and H4-Lys20, the degree of methylation was variable from the mono- to the di- or trimethylated state, each of which was presumed to be involved in the organization of chromatin and the activation or repression of genes. Here we investigated the interplay between histone H4-Lys20 mono- and trimethylation and H4 acetylation at induced (β-major/β-minor globin), repressed (c-myc), and silent (embryonic β-globin) genes during in vitro differentiation of mouse erythroleukemia cells. By using chromatin immunoprecipitation, we found that the β-major and β-minor promoter and the β-globin coding regions as well as the promoter and the transcribed exon 2 regions of the highly expressed c-myc gene were hyperacetylated and monomethylated at H4-Lys20. Although activation of the β-globin gene resulted in an increase in hyperacetylated, monomethylated H4, down-regulation of the c-myc gene did not cause a decrease in hyperacetylated, monomethylated H4-Lys20, thus showing a stable pattern of histone modifications. Immunofluorescence microscopy studies revealed that monomethylated H4-Lys20 mainly overlaps with RNA pol II-stained euchromatic regions, thus indicating an association with transcriptionally engaged chromatin. Our chromatin immunoprecipitation results demonstrated that in contrast to trimethylated H4-Lys20, which was found to inversely correlate with H4 hyperacetylation, H4-Lys20 monomethylation is compatible with histone H4 hyperacetylation and correlates with the transcriptionally active or competent chromatin state. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc.