Title
Conformational flexibility of histone variant CENP-ACse4 regulated by histone H4: a mechanism to stabilise soluble Cse4
Author
Nikita Malik, Sarath Chandra Dantu, Shivangi Shukla, Mamta Kombrabail, Santanu Kumar Ghosh, Guruswamy Krishnamoorthy, Ashutosh Kumar
Year
2018
Journal
Journal of Biological Chemistry
Abstract
The histone variant CENP-ACse4 is a core component of the specialized nucleosome at the centromere in budding yeast and is required for genomic integrity. Accordingly, the levels of Cse4 in cells are tightly regulated, primarily by ubiquitin-mediated proteolysis. However, structural transitions in Cse4 that regulate its centromeric localization and interaction with regulatory components are poorly understood. Using time-resolved fluorescence, NMR, and molecular dynamics simulations, we show here that soluble Cse4 can exist in a “closed” conformation, inaccessible to various regulatory components. We further determined that binding of its obligate partner histone H4, alters the inter-domain interaction within Cse4, enabling an “open” state that is susceptible to proteolysis. This dynamic model allows kinetochore formation only in the presence of H4, as the Cse4 N-terminus, which is required for interaction with other centromeric components, is unavailable in the absence of H4. The specific requirement of H4 binding for the conformational regulation of Cse4 suggests a structure-based regulatory mechanism for Cse4 localization.Our data suggested a novel structural-transition based mechanism where conformational flexibility of the Cse4 N-terminus can control Cse4 levels in the yeast cell and will prevent Cse4 from interacting with kinetochore components at ectopic locations for formation of premature kinetochore assembly.
Instrument
J-1500, FP-6500
Keywords
Circular dichroism, Secondary structure, Protein denaturation, Biochemistry, Fluorescence, Kinetics, Protein structure