Combinatorial patterns of histone acetylations and methylations in the human genome

Abstract
Keji Zhao and colleagues report genome-wide maps of 18 histone lysine acetylations in human CD4+ T cells as detected by ChIP-sequencing. Analysis of the data along with genome-wide maps of histone lysine methylations revealed a common module of 17 modifications associated with 25% of genes. Histones are characterized by numerous posttranslational modifications that influence gene transcription1,2. However, because of the lack of global distribution data in higher eukaryotic systems3, the extent to which gene-specific combinatorial patterns of histone modifications exist remains to be determined. Here, we report the patterns derived from the analysis of 39 histone modifications in human CD4+ T cells. Our data indicate that a large number of patterns are associated with promoters and enhancers. In particular, we identify a common modification module consisting of 17 modifications detected at 3,286 promoters. These modifications tend to colocalize in the genome and correlate with each other at an individual nucleosome level. Genes associated with this module tend to have higher expression, and addition of more modifications to this module is associated with further increased expression. Our data suggest that these histone modifications may act cooperatively to prepare chromatin for transcriptional activation.