FIG 2.

H2A-H2B accumulation protects DNA from MNase digestion. (A) In vitro analysis of chromatin with and without excess H2A-H2B. Shown are data from PAGE analysis of MNase digestion of naked DNA alone, DNA with H2A-H2B, mononucleosomes (Mono-nuc), and mononucleosomes with H2A-H2B, assessed on a 207-bp DNA fragment. (B) Chromatin from wild-type and nap1Δ cells was digested with MNase in vivo, and the cleavage products were analyzed by primer extension assays. Quantitation of the primer extension products from the GAL1 promoter (top) and the GAL10 promoter (bottom) is shown in black for nap1Δ cells and in gray for wild-type cells. The GAL10 promoter, which has excess H2A-H2B as determined by ChIP assays, is more protected from MNase cleavage in nap1Δ cells.