Mapping DNA Target Sites of Chromatin Proteins In Vivo by Formaldehyde Crosslinking

The method described here is based on a technique developed to analyze the chromatin structure of the SV40 origin of replication, and also alterations in nucleosomal structures in the hsp70 promoter of Drosophila after heat shock (1 ,2 ). It relies on the ability of formaldehyde to crosslink proteins and nucleic acids in living cells, from which chromatin can be isolated and protein-DNA interactions probed by immunoprecipitation using specific antibodies.