Release of linker histone from the nucleosome driven by polyelectrolyte competition with a disordered protein

• Published in: Nature chemistry Vol. 14; no. 2; pp. 224 - 231
• Main Authors: Heidarsson, Pétur O., Mercadante, Davide, Sottini, Andrea, Nettels, Daniel, Borgia, Madeleine B., Borgia, Alessandro, Kilic, Sinan, Fierz, Beat, Best, Robert B., Schuler, Benjamin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-02-2022; Nature Publishing Group
• Subjects: 631/114/2397; 631/337/100/1701; 631/57/2265; 639/638/440/56; 639/638/45/953; Affinity; Amplitudes; Analytical Chemistry; Biochemistry; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Chromatin; Competition; Histone H1; Histones; Histones - metabolism; Humans; Inorganic Chemistry; Intrinsically Disordered Proteins - metabolism; Kinetics; Nucleosomes; Nucleosomes - metabolism; Organic Chemistry; Physical Chemistry; Physiology; Polyelectrolytes; Polyelectrolytes - metabolism; Proteins; Proteomes; Transcription
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/s41557-021-00839-3

Highly charged intrinsically disordered proteins are essential regulators of chromatin structure and transcriptional activity. Here we identify a surprising mechanism of molecular competition that relies on the pronounced dynamical disorder present in these polyelectrolytes and their complexes. The highly positively charged human linker histone H1.0 (H1) binds to nucleosomes with ultrahigh affinity, implying residence times incompatible with efficient biological regulation. However, we show that the disordered regions of H1 retain their large-amplitude dynamics when bound to the nucleosome, which enables the highly negatively charged and disordered histone chaperone prothymosin α to efficiently invade the H1–nucleosome complex and displace H1 via a competitive substitution mechanism, vastly accelerating H1 dissociation. By integrating experiments and simulations, we establish a molecular model that rationalizes the remarkable kinetics of this process structurally and dynamically. Given the abundance of polyelectrolyte sequences in the nuclear proteome, this mechanism is likely to be widespread in cellular regulation.
Histone H1 binds to nucleosomes with ultrahigh affinity, implying residence times incompatible with efficient biological regulation. Now it has been shown that the disordered regions of H1 retain their large-amplitude dynamics on the nucleosome, which enables a charged disordered histone chaperone to invade the H1–nucleosome complex and vastly accelerate H1 dissociation.