ORGANIZATION IN YEAST CHROMATIN Abstract approved: Redacted for Privacy

I have investigated nucleoprotein organization in chromatin of the yeast, Saccharomyces cerevisiae. My approach has been to prepare insoluble, minimally per-turbed chromatin from a mitochondrial DNA-free strain of yeast, using a number of new techniques, and then digest this substrate with micrococcal nuclease. The soluble products are electrophoresed on a newly devised high resolution native nucleoprotein gel; DNA and protein constituents of the resolved complexes are analyzed by means of second dimension electrophoresis. I find that yeast nucleoproteins resolve into two bands for each DNA size class, lack a chromatosome, display a distinctive non-random pattern of nuclease excision for dinucleosornes and larger species, and have a markedly reduced complement of mononucleosomes when prepared in this manner. A single non-core protein of about 32,000 daltons appears to be bound to oligonucleosomes, but in modest amount, and primarily on the trinucleosome. A very prominent 40 kilo-dalton protein is selectively released by RNase, but is not associated with oligonucleosomes during native elec-trophoresis. These findings are discussed, with emphasis on nucleosome-nucleosome interactions and mononucleosome stability