Chemical synthesis of the ubiquitinated form of histone H3 and its effect on DNA methyltransferase 1

Histone ubiquitination: Role in genome integrity and chromatin organization

Maintenance of genome integrity is a precise but tedious and complex job for the cell. Several post-translational modifications (PTMs) play vital roles in maintaining the genome integrity. Although ubiquitination is one of the most crucial PTMs, which regulates the localization and stability of the nonhistone proteins in various cellular and developmental processes, ubiquitination of the histones is a pivotal epigenetic event critically regulating chromatin architecture. In addition to genome integrity, importance of ubiquitination of core histones (H2A, H2A, H3, and H4) and linker histone (H1) have been reported in several cellular processes. However, the complex interplay of histone ubiquitination and other PTMs, as well as the intricate chromatin architecture and dynamics, pose a significant challenge to unravel how histone ubiquitination safeguards genome stability. Therefore, further studies are needed to elucidate the interactions between histone ubiquitination and other PTMs, and their role in preserving genome integrity. Here, we review all types of histone ubiquitinations known till date in maintaining genomic integrity during transcription, replication, cell cycle, and DNA damage response processes. In addition, we have also discussed the role of histone ubiquitination in regulating other histone PTMs emphasizing methylation and acetylation as well as their potential implications in chromatin architecture. Further, we have also discussed the involvement of deubiquitination enzymes (DUBs) in controlling histone ubiquitination in modulating cellular processes.

Fmoc-Compatible and C-terminal-Sequence-Independent Peptide Alkyl Thioester Formation Using Cysteinylprolyl Imide

We report an Fmoc-compatible and external-thiol-free method of peptide C-terminus thioesterification with cysteinylprolyl imide. The newly synthesized structure, i.e., cysteinylprolyl-thiazolidinone, provided high conversion and sequence-independent fast kinetics (90 min) in the diketopiperazine thioester formation under relatively mild conditions: pH 6.0, 37 °C. Employing this thioesterification method, we synthesized histone H3.2 bearing K56 acetylation.