Histone modification patterns in highly differentiation cells.

Nucleosomes and modifications on the histones constitute the fundamental genomic structure of eukaryotes. It was reported that particular combinations of histone modifications occurring on the genome indicate specific chromatin states, which are related to a series of cell states. Although the histone code principle has been found for over a decade, the mechanism of the code is not yet known clearly. In this paper, we first conducted an extensive analysis on 38 histone modifications and 1 histone variant in human CD4+ T cells to reveal possible connections among these modifications. Then, we analyzed the different roles that histone modifications play in highly differentiated cells and undifferentiated cells, and found that the number of histone modifications on genes of differentiated cells is correlated to the expression levels of genes, while there is no direct effect of histone modification on gene expression level in undifferentiated cells. Finally, we compared the distributions of histone modifications of CD4+ T cell line and K562 cell line, and observed that they have similar distribution patterns. So we guess that there may exist certain conservative regions of histone modifications. [ABSTRACT FROM AUTHOR]