CELL-GROWTH STIMULATION BY EGF - INHIBITION THROUGH ANTISENSE-OLIGODEOXYNUCLEOTIDES DEMONSTRATES IMPORTANT ROLE OF CASEIN KINASE-II

Casein kinase II (CKII) is a highly conserved ubiquitous serine/threonine kinase composed of two catalytically active subunits (α and/or α′) and two presumably regulatory subunits (β). CKII has numerous cellular functions including a possible role in mitogenic signaling. To address this question, growth-arrested primary human fibroblasts (IMR-90) were exposed prior growth stimulation by epidermal growth factor (EGF) to oligodeoxynucleotides complementary to the translation start region of mRNAs coding for CKII α and β subunits. A significant inhibition of growth stimulation (up to 60%) was observed with both antisense-α and antisense-β. The inhibition was reversible, became decreased with mutated antisense-oligodeoxynucleotides, and neutralized by simultaneous presence of respective senseoligodeoxynucleotides. The expected down-regulation of CKII protein due to hybrid formation of antisense-oligodeoxynucleotides with target mRNAs was investigated by determination of the intracellular protein level of CKII β-subunit by immunofluorescence and quantitative image analysis. The protein was revealed to be localized predominantly in the nucleus and to become significantly decreased due to antisense-β treatment of cells. The maximum decrease coincided with the early phase (first several hours) of growth stimulation by EGF when antisense-β incubation was started 6-2 h before growth stimulation, the period within which application of antisense-α and antisense-β caused the maximum of inhibition of growth stimulation. Thus CKII obviously plays, with both subunit α and subunit β, an important role in the early phase of mitogenic stimulation. © 1991.