Heterochromatin protein 1α (HP1α) is an essential component in the organization of chromatin into the more compact and transcriptionally silenced heterochromatin state. It is believed that this is in part due to HP1α’s ability to undergo liquid-liquid phase separation and form liquid like droplets that selectively manage which other proteins can enter and interact with chromatin inside the droplet. It has also been discovered that HP1α’s propensity to phase separate is modulated through interactions with protein binding partners (PBPs). Shugoshin (Sgo1) is a protein that helps maintain centromere stability during mitosis, and it is also a known PBP of HP1α; however, the details behind its interaction with HP1α and influence on phase separation have not been elucidated. Here, we used various experimental biophysical approaches to study the interactions between full length HP1α and a segment of Sgo1. Fluorescence microscopy experiments showed that Sgo1 can significantly enhance the phase separation properties of HP1α. Paired with binding assays, we also determined the binding affinity between HP1α and Sgo1 and the influence of binding motifs present on Sgo1. Finally, solution nuclear magnetic resonance (NMR) spectroscopy experiments were performed to capture the interactions between the two proteins. Through these experiments, we were able to develop a better understanding of how HP1α binding partners like Sgo1 provide a platform for the regulation of heterochromatin environments.
Dankul et al. (Sun,) studied this question.
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