Expression of the subunits of protein kinase CK2 during oogenesis in Xenopus laevis

ABSTRACT: Northern-blot analysis of RNAs from different tissues demonstrated that the mRNA for the protein kinase CK2α subunit is very abundant in the ovary of Xenopus laevis. The competitive reverse-PCR technique has been used to quantitate the mRNA for both CK2α and CK2β subunits during oogenesis. The results obtained using eight different animals consistently show an increment of 2-3-fold in the mRNA for both subunits in vitellogenic oocytes (stages II-VI). Each stage-VI oocyte contains approximately 5XIOˉ⁷ molecules CK2a mRNA and 1 XIOˉ⁷ molecules CK2β mRNA. These amounts are considerably higher than many other mRNAs analyzed in these cells. Activity measurements of CK2 using casein or a specific model peptide revealed increments of about 10-12-fold during oogenesis, and also indicated that the amount of enzyme in the nucleus accounted for 15-30% of the total enzyme in the oocyte at all stages. Western-blot analysis of CK2α indicated that the amount of this protein subunit also increased during oogenesis in a parallel fashion with the increment of enzymic activity.