Histone chaperones exhibit conserved functionality in nucleosome remodeling

Chromatin homeostasis mediates some of the most fundamental processes in the eukaryotic cell. In this regard, histone chaperones have emerged as major regulatory factors during DNA replication, repair, and transcription. However, the dynamic nature of these processes has severely impeded their characterization at the molecular level. Here we apply single-molecule probing by fluorescence optical tweezers to follow histone chaperone dynamics in real-time. The molecular action of SET/template-activating factor-Iβ and nucleophosmin 1—representing the two most common histone chaperone folds—were examined using both nucleosomes and isolated core histones. We show that these chaperones present binding specificity for partially dismantled nucleosomes and are able to recognize and disrupt non-native histone-DNA interactions. Furthermore, we reveal that cytochrome c inhibition of histone chaperones is coupled to chaperone accumulation on DNA-bound histones. Our single-molecule approach shows that despite the drastically different structures of these chaperones, they present conserved modes of action mediating nucleosome remodeling.