Casein kinase II in signal transduction and cell cycle regulation.

Casein kinase II is a protein serine/threonine kinase that is ubiquitously distributed in eukaryotes. Molecular cloning studies and protein sequence analysis of purified proteins have demonstrated the existence of two related, but distinct, isoenzymic forms of its catalytic subunit in mammals and birds. At present, the precise role of the individual casein kinase II isoforms in biological responses is poorly understood. However, a great deal of evidence indicates that casein kinase II is an important component of signalling pathways that control the growth and division of cells. In particular, casein kinase II is known to phosphorylate, and in several cases, regulate the activity of a variety of regulatory nuclear proteins including nuclear oncoproteins, transcription factors, and enzymes involved in other aspects of DNA metabolism. In this review, we will summarize evidence relating to the involvement of casein kinase II in signal transduction events that are relevant to cell proliferation.