Project Summary The long-term objective of this research program is to elucidate the roles of histone-DNA interactions in gene regulation. The nucleosome, the fundamental packing unit of the eukaryotic genome, imposes physical barriers to DNA access and needs to disassemble at least in part during various nuclear processes such as transcription elongation and chromatin remodeling. The kinetic pathways and rates of these processes are crucial components in gene regulation mechanisms and closely coupled to the dynamics of histone-DNA interactions. Elucidating the implications of dynamic histone-DNA interactions in gene regulation is an important and active subject of the current chromatin research. This project aims to elucidate how spontaneous dynamics of histone-DNA interactions contribute to regulating two important nuclear processes catalyzed by large enzyme complexes that translocate along DNA. The target processes are transcription elongation by RNA polymerase II and chromatin remodeling by INO80 both of which are essential for cell viability and healthy proliferation. The project will reveal how the strong yet dynamic histone-DNA interactions are implicated in regulating these processes based on three-color single-molecule fluorescence resonance energy transfer (smFRET) and single-molecule sub-ms motion analysis. These innovative approaches will enable an understanding of the molecular processes that allow these enzymes to access and act on nucleosomes and the end products of their activities at an unprecedented level of depth.