Fig. 7

OND does not induce core histone displacement from chromatin but does decrease the mobility of the linker histone H1. We first demonstrated that HeLa cells stably transfected with either histone H2B-mCherry or histone H1.1-green fluorescent protein (GFP) respond to 1 hour of OND by undergoing chromatin compaction. a Comparison of untreated (UT) cells (top panels) with cells exposed to 1 hour of OND (bottom panels) by confocal microscopy clearly indicates that chromatin of HeLa cells compacts upon OND treatment. b We then evaluated the mobility of the core histone H2B using FRAP on untreated (upper panel) and on OND-treated (lower panel) cells. The recovery after photobleaching was extremely slow for both conditions, indicating that OND does not induce displacement of H2B from chromatin. c We then evaluated the mobility of the linker histone H1 in untreated and OND-treated HeLa cells. As previously reported [49, 50], histone H1 is mobile, and is somewhat less mobile in heterochromatin than in euchromatin. d OND-induced chromatin compaction dramatically reduces the mobility of histone H1, indicating that the extent of chromatin compaction in OND is considerably higher than that between euchromatin and heterochromatin