The emerging CK2 interactome: insights into the regulation and functions of CK2

Protein kinase CK2 represents a small family of protein serine/threonine kinases implicated in a variety of biological processes including events relating to cell proliferation and survival. Notably, CK2 displays oncogenic activity in mice and exhibits altered expression in several types of cancer. Accordingly, a detailed understanding of the cellular functions of CK2 and elucidation of the mechanisms by which CK2 is regulated in cells is expected to contribute to understanding its role in tumorigenesis with the prospect of novel approaches to therapy. While CK2 has traditionally been viewed as a tetrameric complex composed of two catalytic and two regulatory subunits, mounting evidence suggests that its subunits may have functions independent of tetrameric CK2 complexes. In mammals, as is the case in the budding yeast Saccharomyces cerevisiae, there are two isozymic forms of CK2, adding additional heterogeneity to the CK2 family. Studies in yeast and in human cells demonstrate that the different forms of CK2 interact with a large number of cellular proteins. To reveal new insights regarding the regulation and functions of different forms of CK2, we have examined the emerging interactomes for each of the CK2 subunits. Analysis of these interactomes for both yeast and human CK2 reinforces the view that this family of enzymes participates in a broad spectrum of cellular events. Furthermore, while there is considerable overlap between the interactomes of the individual CK2 subunits, notable differences in each of the individual interactomes provides additional evidence for functional specialization for the individual forms of CK2.