Volume 10 Issue 10, October 2009

Ubiquitin-binding domains (UBDs) are modular elements that bind non-covalently to the protein modifier ubiquitin. Recent structures of ubiquitin–UBD complexes at atomic-level resolution reveal some of the mechanisms that underlie the versatile functions of ubiquitinin vivo.

Stem cell differentiation and the maintenance of self-renewal are intrinsically complex processes. They require the coordinated and dynamic expression of hundreds of genes and proteins, in precise response to external signalling cues. Systems biology approaches are helping to dissect this complexity.

Kinesins are molecular motors that directionally transport various cargos, including membranous organelles, protein complexes and mRNAs. The mechanisms by which kinesins recognize, bind and unload cargo, and also regulate processes such as higher brain function, tumour suppression and developmental patterning, are becoming clear.

Polycomb group (PcG) proteins constitute a conserved gene silencing system with widespread roles in multicellular development, stem cell biology and cancer. Recent studies suggest that PcG-mediated gene silencing may involve histone modifications and a possible block in transcriptional elongation.

Amino acid substitutions in divergent protein families reflect both Darwinian selection and neutral evolution. The latter operates within structural and functional constraints and arises from the need to conserve protein architecture and interactions that are important for the survival of the organism.

Protein denitrosylation, the removal of nitric oxide groups from Cys thiols, was once considered to be a spontaneous event. Now, the discovery of denitrosylases, the enzymes that catalyse this process, is advancing our understanding of redox-based signalling in normal and aberrant cellular functions.