We are interested in understanding how gene expression is regulated. Our main research goal is to understand the molecular mechanisms responsible for assembly and disassembly of transcription preinitiation complexes at promoters, a major regulatory step in the complex process of RNA synthesis. Much of our work exploits the budding yeast system, although we also work with human cells as well. Our analysis of transcription preinitiation complex assembly led us to consider fundamental questions about chromatin binding dynamics in cells. We seek to understand not only pathways for assembly and activity of transcription complexes in vivo, but the time scales on which these processes occur, how efficient they are in a cell population, and how stable complexes are once they assemble on chromatin. To address these questions, we developed a method that allows us to measure chromatin binding kinetics at specific chromosomal sites in cells. We also have a longstanding interest in the molecular mechanisms of regulatory factors that control transcription complex assembly, which we address using combined biochemical, biophysical, molecular, genetic and genomic experimental approaches.