Polo boxes come out of the crypt: a new view of PLK function and evolution.

Polo-like kinases (PLKs) are marked by C-terminal polo box modules with critical protein interaction and subcellular targeting roles. Slevin et al. in this issue of Structure reveal the architecture of a hidden set of polo boxes from the divergent PLK4, a critical player in centrosome duplication, shedding new light on the evolution of PLKs and their functionally related kinase ZYG-1.