Analysis of gamma-satellite DNA in human cells. (A) ChIP analysis of gamma-satellite DNA arrays on chromosome X in human dermal fibroblasts. Enrichment was normalized to enrichment at ZXDA, the most proximal human gene on Xp located in euchromatin. ChIP was performed at least three times and PCRs were done in duplicate for antibodies in each ChIP. (B,C) Gamma satellite is incorporated into chromatin-containing euchromatic histone modifications. Immunofluorescence-FISH on chromatin fibers was performed to spatially define the location of gamma-satellite and histone markers of euchromatin on human chromosomes in human dermal fibroblats. H3K4me2 antibody staining (green) and H3K4me3 antibody staining colocalize with a DNA probe specific for the human X gamma-satellite array (red). While chromatin containing H3K4 methylation is concentrated at the gamma-satellite array, it also extends past the array, suggesting that nearby pericentromeric sequences are also incorporated into open chromatin. Scale bar, 5 microns (B) and 15 microns (C).