THE MULTIFUNCTIONAL REGULATORY PROTEINS ABF1 AND CPF1 ARE INVOLVED INTHE FORMATION OF A NUCLEASE-HYPERSENSITIVE REGION IN THE PROMOTER OF THE QCR8 GENE

The abundant DNA-binding proteins ABF1 and CPF1 are members of a famil y of global regulators with diverse chromosomal functions in the yeast Saccharomyces cerevisiae. Recent evidence suggests that these protein factors may be involved in establishing and maintaining well-defined chromatin structures in promoter regions and other genetic elements. W e have investigated the involvement of ABF1 and CPF1 in chromatin orga nization at the QCR8 gene, encoding subunit VIII of the mitochondrial ubiquinol-cytochrome c oxidoreductase. The promoter region of the QCR8 gene contains overlapping binding sites for ABF1 and CPF1. Nucleosome positioning studies indicate that the QCR8 gene is associated with a phased array of nucleosomes under both catabolite-repressed and derepr essed growth conditions. Analysis of binding site mutants reveals that both ABF1 and CPF1 are involved in maintaining a nuclease-hypersensit ive region in the QCR8 promoter. The chromatin structure at QCR8 durin g steady-state growth is, however, mainly dependent on binding of ABF1 to the promoter region. Implications of these findings for the role p layed by ABF1 and CPF1 in the regulation of mitochondrial biogenesis a nd other processes important for cell growth and division will be disc ussed.