Relative histone H2B ChIP values (band intensity ratios, indicated experimental locus/ control locus 66 kb from the DSB; see Supplemental Experimental Procedures) were measured in samples taken from cycling cells (H1069) before (0 min, open circles) or 60 min after (closed circles) HO induction; a strain in which about half of all histones H2B are tagged with a single HA epitope (H1069) was used. For comparative purposes, relative γ-H2AX ChIP levels in a 60 min sample are reproduced from Figure 2A. (Inset) Representative multiplex PCR reactions with H2B ChIP samples: +, ChIP samples; −, primary antibody omitted; in, 100-fold dilution of input lysate. DSB-specific PCR primers were for sequences 0.02 kb from the DSB.