Binding specificity of ASHH2 CW-domain towards H3K4me1 ligand is coupled to its structural stability through its α1-helix [article]

Maxim S Bril'kov, Olena Dobrovolska, Oeyvind Oedegaard-Fougner, Oeyvind Stroemland, Rein Aasland, Oeyvind Halskau
2021 bioRxiv   pre-print
The CW domain binds to histone-tail modifications found in different protein families involved in epigenetic regulation and chromatin remodelling. CW domains recognize the methylation state of the fourth lysine on histone 3, and as such could be viewed as a reader of epigentic information. The specificity towards different methylation states such as me1, me2 or me3 depend on the particular subtype. For example, the CW domain of ASHH2-methyltransferase binds preferentially to H3K4me1, MORC3
more » ... to both H3K4me2 and me3 modifications, while ZCWPW1 is more specific to H3K4me3. The structural basis for these preferential bindings are not understood well, and recent research suggests that a more complete picture will emerge if dynamical and energetic assessments are included in analysis of interactions. This study uses fold assessment by NMR in combination with mutagenesis, ITC affinity measurements and thermal denaturation studies to investigate possible couplings between ASHH2 CW selectivity towards H3K4me1, and the stabilization of the domain. Key elements of the binding site are the two tryptophans and the a1-helix form and maintain the binding pocket were perturbed by mutagenesis and investigated. Results show that a1-helix maintains the overall stability of the fold via the I915 and L919 residues, and that correct binding consolidates the coils designated n1, n3, as well a the C-terminal. This consolidation is incomplete for H3K4me3 binding to CW, which experiences a decrease in overall thermal stability upon binding. Moreover, loop-mutations not directly involved in the binding site nonetheless affect the equilibrium positions of key residues.
doi:10.1101/2021.08.12.456084 fatcat:bive5iywdfdbfehlore3iqvbtu