Changes of chromatin organization induced by phospholipids.

Isolated nuclei represent a suitable model for studying the influence of exogenous phospholipids, normally found as minor chromatin components, on the nuclear structure, which, in turn, could be related to the observed modifications of DNA and RNA synthesis. The morphological modifications induced on chromatin RNP granules and nuclear matrix have been analyzed both with conventional thin sectioning and with an original method based on image analysis of freeze-fractured and replicated nuclear samples. The results obtained support the hypothesis that anionic phospholipids, by removing histone H1, induce a transition of the chromatin from solenoid to nucleosome conformation and favour the RNA polymerizing activity which results in an increased release of RNP particles, while neutral phospholipids, probably affecting the matrix structure, partly impare the RNP maturation and transport, with consequent increase of chromatin condensation.