Role of Chromatin Structure in the Regulation of an Acid Phosphatase Gene in Yeast

Abstract

The chromatin structure in the promoter region of PHO5, the structural gene for a strongly regulated acid phosphatase in yeast, was analyzed. An upstream activating sequence 367 base pairs (bp) away from the start of the coding sequence that is essential for gene induction (Rudolph and Hinnen 1986) was found to reside in the center of a hypersensitive region under conditions of PHO5 repression. With these conditions three related elements at positions −469, −245, −185 are contained within precisely positioned nucleosomes located on both sides of the hypersensitive region. Upon PHO5 induction the chromatin structure of the promoter undergoes a defined transition, in the course of which two nucleosomes upstream and two nucleosomes downstream of the hypersensitive site are selectively removed. In this way approximately 600 bp upstream of the PHO5 coding sequence become highly accessible, and all four elements are free to interact with putative regulatory proteins. These findings suggest a mechanism by which the chromatin structure participates in the functioning of a regulated promoter.