The immunospecificity of nonhistone protein complexes with DNA.

Abstract

It has been suggested that nuclear nonhistone proteins participate in maintaining the differentiated state of cells. They were shown by electrophoretic criteria to be tissue and species specific, and the presence of certain nonhistone proteins in reconstituted chromatin was found to be necessary for the in vitro transcription of tissue-specific RNA species (detectable by DNA-RNA hybridization)1–3. The mixture of nonhistone proteins and DNA (NP-DNA) resulting from the dehistonization of chromatin has been shown by complement fixation to be tissue specific4. Furthermore, the unique ability of chick oviduct chromatin to receive and bind the progesteronecytosol protein complexes is associated with the fraction of nonhistone proteins which is responsible for the immunospecificity of chromatin6. In this communication we show that the immunochemical detection of tissue specificity of chromatin as reported by Chytil and Spelsberg4 recognizes nonhistone protein complexes with homologous DNA. The chromatin nonhistone proteins alone or complexed with heterologous DNA, RNA, or other polyanions are immunochemically incompetent if assayed with antibodies obtained by injecting the rabbits with the mixture of nonhistone proteins and DNA (NP-DNA pellet).