Full and partial genome-wide assembly and disassembly of the yeast transcription machinery in response to heat shock

Eukaryotic genes are controlled by sequence-specific DNA-binding proteins, chromatin regulators, general transcription factors, and elongation factors. Here we examine the genome-wide location of representative members of these groups and their redistribution when the Saccharomyces cerevisiae genome is reprogrammed by heat shock. As expected, assembly of active transcription complexes are coupled to eviction of H2A.Z nucleosomes, and disassembly is coupled to the return of nucleosomes. Remarkably, a large number of promoters assemble and disassemble into partial pre-initiation complexes (partial PICs), containing TFIIA, TFIID (and/or SAGA), TFIIB, TFIIE, and TFIIF. At these promoters, neither TFIIH nor RNA polymerase II are recruited, and nucleosomes are not displaced. These promoters may be preparing for additional stress that naturally accompany heat stress. For example, we find that oxidative stress, which often occurs with prolonged exposure of cells to high temperature, coverts partial PICs into full PICs. Partial PICs therefore represent novel regulated intermediates that assemble in the midst of chromatin. Keywords: other