Yeast Chromatin

Abstract

A chromatin‐like material was prepared from isolated nuclei of Saccharomyces cerevisiae. This chromatin fraction contains a full complement of yeast histones as revealed by acrylamide‐gel electrophoresis. Yeast histones were found to resemble those of rat liver cells in electrophoretic properties except for the almost complete absence of histone F1. Yeast chromatin is only poorly transcribed by the isolated yeast RNA polymerases A and B and was found to contain endogenous RNA polymerases which are activated by the addition of salts. Salt causes a removal of DNA‐associated proteins from the chromatin, allowing bound RNA polymerase molecules to extend already initiated RNA chains. Some evidence was obtained indicating that different proteins have to be removed to allow the different endogenous polymerases to proceed with transcription. It is concluded that the properties of yeast chromatin studied, in particular the histone composition and the transcription capacity, are very similar to those of chromatin preparations from animal cells.