Katherine Stott

Organisational and regulatory roles of disordered proteins.

Intrinsically disordered proteins play essential roles in cellular function, yet their mechanisms remain poorly understood compared to their structured counterparts. While structured proteins are often depicted as stable three-dimensional arrangements of alpha helices and beta sheets that interact through complementary surfaces, a significant portion of the proteome consists of proteins that lack fixed structures. These disordered proteins or regions are not simply "unfolded" but operate through distinct mechanisms critical to numerous biological processes.

Our research addresses a fundamental question: "How is function encoded in disordered regions?" This represents a significant challenge in molecular biology. For folded proteins, established structural biology approaches allow us to connect sequence to structure and function. Machine learning methods that analyse evolutionary conservation patterns have accelerated this understanding. However, disordered proteins present a unique challenge because they exist as dynamic ensembles rather than single structures, subjecting their sequences to more subtle evolutionary constraints.

We focus on two biological systems where disordered proteins play pivotal roles. First, we study chromatin architecture, where disordered protein regions help organize and compact DNA within the nucleus. Second, we investigate how disordered proteins scaffold signalling complexes, bringing together enzymes and substrates to facilitate cellular communication. In both areas, the disordered components often represent the least understood aspects of these molecular assemblies.

Our methodological approach integrates multiple biophysical techniques to capture the dynamic nature of these systems. We employ solution-state X-ray and neutron scattering to observe overall molecular dimensions and shapes. Nuclear Magnetic Resonance (NMR) spectroscopy provides atomic-level insights into local structure and interactions. We leverage both in-house facilities and specialized equipment at national and international research centres to build comprehensive models of these challenging systems.

Recent findings from our laboratory have advanced understanding of chromatin organization. We've developed models demonstrating how the disordered tails of linker histones form ‘fuzzy complexes’ with DNA, acting like a DNA ‘liquid glue’ and contributing to chromatin condensation through phase separation processes³. Our work reveals how this system is regulated by phosphorylation and histone variants¹, providing insights into the molecular basis of gene regulation. Similarly, our research on calcineurin scaffolding illustrates how disordered regions coordinate signalling components into functional assemblies².

Research objectives

• To establish the drivers of DNA condensation that impact chromatin architecture and gene expression.

• To develop a toolkit to describe the structure, molecular recognition processes, dynamics and functional impact of 'fuzzy complexes'.

• To understand how disordered scaffold proteins assemble and regulate signalling complexes, and to develop molecular tools to disrupt them.

Key publications

¹Watson M, Sabirova D, Hardy MC, Pan Y, Yates H, Wright CJ, Chan WH, Destan E & Stott K (2024). A DNA condensation code for linker histones. Proc. Natl. Acad. Sci. U.S.A., 121(33) e2409167121. doi: 10.1073/pnas.2409167121

²Watson M, Almeida TB, Ray A, Hanack C, Elston R, Btesh J, McNaughton PA & Stott K (2022). Hidden multivalency in phosphatase recruitment by a disordered AKAP scaffold. J. Mol. Biol., 434(16), 167682. doi: 10.1016/j.jmb.2022.167682

Watson M, Stott K (2019). Disordered domains in chromatin-binding proteins. Essays Biochem., 63(1):147-156. doi: 10.1042/EBC20180068

³Turner AL, Watson M, Wilkins OG, Cato L, Travers A, Thomas JO, Stott K (2018). Highly disordered histone H1-DNA model complexes and their condensates. Proc. Natl. Acad. Sci. U.S.A., 115(47):11964-11969. doi: 10.1073/pnas.1805943115, and associated commentary: 10.1073/pnas.1816936115

Stott K, Watson M, Bostock MJ, Mortensen SA, Travers A, Grasser KD, Thomas JO (2014). Structural insights into the mechanism of negative regulation of single-box high mobility group proteins by the acidic tail domain. J. Biol. Chem., 289(43):29817-29826. doi: 10.1074/jbc.M114.591115

Thomas JO, Stott K (2012). H1 and HMGB1: modulators of chromatin structure. Biochem. Soc. Trans., 40(2):341-346. doi: 10.1042/BST20120014