X inactivation is associated with chromosome-wide establishment of inactive 
chromatin. Although this is classically regarded as facultative heterochromatin 
that is uniform in nature, the exact distribution of associated epigenetic marks 
is not well defined. Here we have analysed histone modifications in human 
somatic cells within two selected regions of the X chromosome. Intergenic, 
coding and promoter regions are segregated into differentially marked chromatin. 
H3K27me3 is most prominent in intergenic and silenced coding regions, but is 
associated with some active coding regions as well. Histone H3/H4 acetylation 
and H3K4me3 are locally enriched at promoter regions but do not necessarily mark 
continuing transcription. Remarkably, H3K9me3 is predominant in coding regions 
of active genes, a phenomenon that is not restricted to the X chromosome. These 
results argue against the exclusiveness of individual marks to heterochromatin 
or euchromatin, but rather suggest that composite patterns of interdependent or 
mutually exclusive modifications together signal the gene expression status.