Expression and function of casein kinase II in mouse oocytes

Casein Kinase 2 (CK2) is a ubiquitous and messenger-independent serine/threonine kinase whose substrates play important roles in cell cycle regulation. This tetrameric enzyme is composed of two α and β subunits. The α subunits are the catalytic portion of the enzyme while the β subunits appears to play a role in enhancing the catalytic activity and stability of CK2, and in modulation of the substrate requirement. Although no major fluctuations of CK2 activity appear occur during different stages of the cell cycle, a series of evidence indicate that CK2 is an important component of regulatory protein kinase networks that are involved in mitotic cycle progression. There are a number of indications that CK2 is implicated in G2/M transition and Cdk1 activation pathway in somatic cells. Indeed, CK2 phosphorylates Wee1, a negative regulator of Cdk1, at the onset of M phase, accelerating its degradation through proteasome pathway. In addition, CK2 phosphorylates also CDC25B, the starter of mitosis, increasing the catalytic activity of this phosphatase. CK2 subunits appear to be physiological substrates of Cdk1 both in vitro and in vivo. Cdk1 plays a major role in mouse meiosis resumption and its activation is preceded by a drop of intraoocyte cAMP level. Here we have investigated whether CK2 could play a role in meiotic progression control of mouse oocytes.