Total chemical synthesis of bivalently modified H3 by improved three-segment native chemical ligation

Based on the efficient synthesis of H3 segment with pseudo dipeptide incorporation, we have developed a practical strategy for three-segment-directed total chemical synthesis of H3 bearing trimethylation and acylation. Subsequently we reconstituted it into nucleosome successfully with good homogeneity. [Display omitted] The H3 bivalent modifications of trimethylation at Lys9 and acetylation at Lys18 (H3-K9Me3-K18Ac) were identified to collectively recruit TRIM33 in the nodal signaling pathway. To understand the underlying mechanism of TRIM33 recruitment, the nucleosome core particles (NCPs) containing full-length H3-K9Me3-K18Ac were indispensable samples. Herein we developed a pseudo dipeptide strategy to efficiently prepare peptide segments, facilitating the chemical synthesis of H3-K9Me3-K18Ac at a tens of milligram scale. The synthetic H3-K9Me3-K18Ac was then examined by CD spectroscopy, which demonstrated a prominent shift compared to recombinant H3. Finally, bivalently modified NCPs were assembled and verified by gel mobility shift assay with good homogeneity.