12] Use of antihistone antibodies with nucleosomes

Abstract

Antibodies directed against defined regions of histone molecules represent one of the most specific probes for studying the surface topography of nucleosomes and chromatin and for monitoring post-translational histone modifications. Antibodies directed against the epitopes can be used to determine the regions of histone molecules that are exposed at the surface of nucleosomes and are useful probes for analysing chromatin structure and function. Four approaches have been used to obtain antibodies suitable for these types of studies: (1) immunization with histone molecules, (2) immunization with synthetic peptide fragments of histones, (3) immunization with nucleosomes, and (4) preparation of hybridomas from nonimmunized, autoimmune mice. The method used for purifying histones and the immunization protocol, using histones complexed with RNA, influence the conformation of histone molecules and will thus affect their antigenic determinants. There is also evidence that polymerization of histones into chromatin components produces novel antigenic determinants that derive their specificity from the tertiary and quaternary structure. Changes in environmental conditions that alter the structure of chromatin or posttranslational modifications can thus be expected to modify its antigenic reactivity.