FIXATION-DEPENDENT ORGANIZATION OF CORE HISTONES FOLLOWING DNA FLUORESCENT IN-SITU HYBRIDIZATION

We have evaluated the effects of different DNA denaturation protocols commonly used in DNA fluorescent in situ hybridization (FISH) experime nts on chromatin structure using indirect immunofluorescence. The use of antibodies to acetylated histones H3 and H4 demonstrates that the d ifferent procedures differ considerably in their extent of histone dis placement. Procedures involving paraformaldehyde fixation were found t o be compatible with the structural preservation of acetylated chromat in organization by indirect immunofluorescence. These results provide a basis for interpreting DNA FISH experiments aimed at determining chr omatin organization of individual loci.