Changes in casein kinase 2 activity during development of the secondary palate in the hamster

Abstract

Background Casein kinase 2 (CK 2) is a serine/threonine kinase that has been ubiquitously conserved in all eukaryotic cells. The exact functions of this enzyme have not yet been clarified; however, studies have repeatedly suggested that it may play crucial roles in the regulation of cell proliferation. During the formation of the secondary palate in the hamster, bursts of cell proliferation occur during the initial half of vertical shelf development, which decrease during the subsequent steps of palate morphogenesis, thus indicating that the cell cycle in the developing vertical palate may be tightly regulated. Methods In the present study, palatal shelves were dissected at 12‐hour intervals between days 10 and 12 of gestation, which is the period of vertical shelf development in the hamster. The palates were homogenized and cleared by ultracentrifugation and the resultant supernatants were fractionated on a Mono Q column by fast protein liquid chromatography. Results Using phosvitin as a substrate, the phosphotransferase activity in the fractionated samples decreased steadily from days 10 to 11, increased to a fivefold peak on day 11:12, and then decreased on day 12 of gestation. Western blot analysis using two CK 2 specific antibodies demonstrated that both the 42‐kDa (α) and the 38‐kDa (α′) subunits of the CK 2 holoenzyme were found throughout the formation of the vertical palatal shelves in the hamster. The amount of α and α′ subunits appears to remain constant, which suggested that the differential activity of the CK 2 enzyme may be due to posttranslational modifications. CK 2 activity correlated well with DNA synthesis (i.e., cell proliferation) rates from days 10 to 11, but not from days 11 to 12 of gestation. Conclusions It is proposed that the activity of CK 2 may regulate the rate of cell proliferation by stimulation of progression through G1 phase of the cell cycle and may also relate to the effects of various growth factors during the vertical development of mammalian palate. © 1996 Wiley‐Liss, Inc.

Effects of EGF and TGF?1 onc-myc gene expression and DNA synthesis in embryonic hamster palate mesenchymal cells

“…in regulation of c‐myc expression (Luscher et al, 1989; Barone and Courtneidge, 1995; Lemaitre et al, 1996). EGF also activates PKC (Chepenik and Grunwald, 1988; Chepenik and Haystead, 1989), MAPK and CK2 (Shah et al, 1995a,b; Young et al, 1996a,b) in palate mesenchymal cells of mammals, as well as that from other vertebrates (Hehn et al, 1995, 1996). Although not yet determined in palate mesenchymal cells, EGF/serum activation of these signalling pathways in other eukaryotic cells stimulate expression of c‐myc (Luscher et al, 1989; Barone and Courtneidge, 1995; Lemaitre et al, 1996) that seems to be necessary for progression of cells into G1 phase, and for eventual regulation of cell proliferation (Treisman, 1994, 1996).…”