Cucurbit[7]uril-Dimethyllysine Recognition in a Model Protein

Advances and Opportunities in Epigenetic Chemical Biology

The study of epigenetics has greatly benefited from the development and application of various chemical biology approaches. In this review, we highlight the key targets for modulation and recent methods developed to enact such modulation. We discuss various chemical biology techniques to study DNA methylation and the post-translational modification of histones as well as their effect on gene expression. Additionally, we address the wealth of protein synthesis approaches to yield histones and nucleosomes bearing epigenetic modifications. Throughout, we highlight targets that present opportunities for the chemical biology community, as well as exciting new approaches that will provide additional insight into the roles of epigenetic marks.

Oligomeric Cucurbituril Complexes: from Peculiar Assemblies to Emerging Applications

Proteins are an endless source of inspiration. By carefully tuning the amino-acid sequence of proteins, nature made them evolve from primary to quaternary structures, a property specific to protein oligomers and often crucial to accomplish their function. On the other hand, the synthetic macrocycles cucurbiturils (CBs) have shown outstanding recognition properties in water, and a growing number of (host)_n :(guest)_n supramolecular polymers involving CBs have been reported. However, the burgeoning field of discrete (n:n) host:guest oligomers has just started to attract attention. While 2:2 complexes are the major oligomers, 3:3 and up to 6:6 oligomers have been described, some associated with emerging applications, specific to the (n:n) arrangements. Design rules to target (n:n) host:guest oligomers are proposed toward new advanced host:guest systems.

Infinite Assembly of Folded Proteins in Evolution, Disease, and Engineering

Mutations and changes in a protein's environment are well known for their potential to induce misfolding and aggregation, including amyloid formation. Alternatively, such perturbations can trigger new interactions that lead to the polymerization of folded proteins. In contrast to aggregation, this process does not require misfolding and, to highlight this difference, we refer to it as agglomeration. This term encompasses the amorphous assembly of folded proteins as well as the polymerization in one, two, or three dimensions. We stress the remarkable potential of symmetric homo-oligomers to agglomerate even by single surface point mutations, and we review the double-edged nature of this potential: how aberrant assemblies resulting from agglomeration can lead to disease, but also how agglomeration can serve in cellular adaptation and be exploited for the rational design of novel biomaterials.

Cucurbit[8]uril Reactivation of an Inactivated Caspase-8 Mutant Reveals Differentiated Enzymatic Substrate Processing

Caspase-8 constructs featuring an N-terminal FGG sequence allow for selective twofold recognition by cucurbit[8]uril, which leads to an increase of the enzymatic activity in a cucurbit[8]uril dose-dependent manner. This supramolecular switching has enabled for the first time the study of the same caspase-8 in its two extreme states; as full monomer and as cucurbit[8]uril induced dimer. A mutated, fully monomeric caspase-8 (D384A), which is enzymatically inactive towards its natural substrate caspase-3, could be fully reactivated upon addition of cucurbit[8]uril. In its monomeric state caspase-8 (D384A) still processes a small synthetic substrate, but not the natural caspase-3 substrate, highlighting the close interplay between protein dimerization and active site rearrangement for substrate selectivity. The ability to switch the caspase-8 activity by a supramolecular system thus provides a flexible approach to studying the activity of a protein at different oligomerization states.