%0 Journal Article
%T Ubiquitin ligases and beyond
%A Ivan Dikic
%A Miranda Robertson
%J BMC Biology
%D 2012
%I BioMed Central
%R 10.1186/1741-7007-10-22
%X Pickart's article marked the expansion of ubiquitination from what most regarded as a niche preoccupation, with implications only for housekeeping protein turnover and the destruction of damaged ribosomal products, to seize the attention and excite the imagination of researchers in every area of cell biology. Comparisons to phosphorylation are rife - specific ubiquitin ligases promote ubiquitination and deubiquitinating enzymes terminate its effects of ubiquitination just as ubiquitination just as kinases and phosphatases induce and terminate the effects of phosphorylation - though ubiquitination, unlike phosphorylation, can operate irreversibly, by delivering its targets to the proteasome: hence its vital role in the progression of the cell cycle.It was already clear in 2004 that the number of ubiquitinating and deubiquitinating enzymes was very large, and that ubiquitin tags can be attached to proteins either as monomers or as poly-ubiquitin chains. But it had only recently been discovered that there are at least seven different kinds of poly-ubiquitin chains, and how the diversity of poly-ubiquitin signals is generated and interpreted in cells was in large part territory still to be explored.In a series of articles the first three of which are published this month, we review what is now known about some of the central issues in research on ubiquitination, revisiting the questions of how ubiquitin signals are conjugated to and removed from specific targets, and how they are recognized and contribute to the regulation of central processes in cells.Ubiquitin is a protein of 76 amino acids whose structure is shown in Figure 1. It is attached to a lysine in its target proteins either as a monomer or as a poly-ubiquitin chain each monomer of which is linked through its carboxy-terminal glycine to (usually) a lysine in the preceding ubiquitin in the chain. Three enzymes, known generically as E1, E2 and E3, act in series to catalyze ubiquitination (Figure 2). The E1 is t
%U http://www.biomedcentral.com/1741-7007/10/22