The broad purpose of this project is to understand the way in which chromatin, the DNA-protein complex in the nucleus of higher organisms, operates to establish and maintain regulated cell function. Investigations are in progress to understand chromatin structure, i.e. the specific organization of proteins and DNA within the complex and the relationship of this structure to biological functions. The biological function of present interest is control of gene expression; the proteins of chromatin serve to block certain gene sequences from being transcribed into messenger RNA. This is believed to form the chemical basis of cell differentiation. One test system being investigated is globin messenger RNA synthesis in chromatin from avian reticulocytes. The goal is to isolate the biochemical factors in this chromatin responsible for maintaining globin message synthesis, and to understand how these factors affect chromatin structure to carry out their function. Other related studies are concerned with the folding of DNA by chromatin proteins, the physical arrangement of proteins on the globin gene, and the effects of these proteins on the transcription processes.