Fig. 1.

Human α-satellite DNA is assembled into CEN chromatin, euchromatin, and heterochromatin. (A) ChIP-PCR of histone modifications at α-satellite DNA from chromosomes X, 7, and 17 in cell lines HT1080, X4, and X5. Bar graphs show relative enrichment (>1). Baseline enrichment was set at 1 (dashed line) (see Methods). ChIP-PCR was performed three times; averages are shown with standard deviation bars. (B–D) Optical mapping on extended chromatin fibers shows that CENP-A (red) occupies a fraction of the α-satellite array (DXZ1) of the human X chromosome. H3K9me2 (green) is closely located at one (C) or both (D) sides of the CEN chromatin domain marked by CENP-A (red), suggesting that α-satellite DNA is also assembled into heterochromatin. (Scale bar, 10 μm.)