WD40 and CUL4-based E3 ligases: lubricating all aspects of life.

The ubiquitin proteasome pathway is one of the major regulatory tools used by eukaryotic cells. E3 ligases, which allow controlled modification of proteins with ubiquitin, are crucial for the specificity of the pathway. Recently, an additional plant cullin-based E3 ligase complex was described which contains cullin 4 (CUL4) and DAMAGED DNA BINDING 1 protein as core subunits. Our knowledge of this E3 ligase has increased tremendously since its first description, and it seems to be involved in many developmental and physiological processes. Here, we review the most recent studies on CUL4 E3 complexes, with a focus on their substrate recognition and the plethora of processes that they regulate in plants, such as photomorphogenesis, flowering and abiotic stress response.