UC San Diego

Histone proteins in chromatin undergo various modifications that have profound impacts on many cellular processes, including cell cycle control, cancer, senescence, X-inactivation, cell fate decisions, and stem cell differentiation. These histone marks do not occur isolated, but often occur mutually exclusive or concurrently. Despite the extensive research ongoing, a large part of the regulation of histone marks remained elusive due to the lack of powerful and efficient methods. Here, we present a method of constructing an epigenetic fluorescence energy resonance transfer (FRET) biosensor by tuning variables including the linker length and orientations between the fluorescent proteins in the case of a H3K27me3 FRET biosensor. It reveals that shortening the linker connecting the fluorescent protein pairs and binding partners could indeed increase the FRET change between the bound and unbound states in the biosensor. This key concept can be generally applied to optimize various different FRET biosensors, especially histone epigenetic FRET biosensors with binding domains that have relatively low binding affinities.