UC Riverside

Eukaryotic chromatin is packaged within the nucleus in the form of a highly organized structure, with nucleosomes as basic units. Each nucleosome is comprised of an octamer of histone proteins, wrapped by 147-base pair DNA. The chromatin environment, orchestrated by high-order nucleosome assembly, critically influences various genome activities, such as epigenetic regulation. Increasing evidence has indicated that the multivalent interaction between an epigenetic modifier or effector and the nucleosome array dictates the epigenetic states, and consequently, genome organization and gene activity. To date, due to the complexity of high-order nucleosome assembly, the structure and mechanism of epigenetic complexes have mostly been characterized at the mono- and/or dinucleosome level, which has limited our mechanistic understanding of their nucleosome interactions in a native chromatin environment. To extend this limit, we have reconstituted an epigenetically modified tetranucleosome for protein interaction. In preliminary studies, we measured the nucleosome-binding affinity of two heterochromatin factors using the electrophoretic mobility shift assay (EMSA). Our long-term goal is to deepen the understanding of how multivalent protein-nucleosome interactions contribute to epigenetic modification and genome organization in cells.