Abstract
The chromatin structure of TDH3, one of three genes encoding glyceraldehyde phosphate dehydrogenases in Saccharomyces cerevisiae, was analyzed by nuclease digestion. A large hypersensitive region was found at the TDH3 promoter extending from the RNA initiation site at position -40 to position -560. This hypersensitive domain is nucleosome free and includes all putative cis-acting regulatory DNA elements. It is equally present in cells grown on fermentable as well as nonfermentable carbon sources. In a mutant which lacks the trans-activating protein GCR1 and which as a consequence expresses TDH3 at less than 5% of the wild-type level, the chromatin structure is different. Hypersensitivity between -40 and -370 is lost, due to the deposition of nucleosomes on a stretch that is nucleosome free in wild-type cells. Hypersensitivity is retained, however, further upstream (from -370 to -560). A similarly altered chromatin structure, as in a ger1 mutant, is found in wild-type cells when they approach stationary phase. This is the first evidence for a growth-dependent regulation of the TDH3 promoter.