ORNITHINE DECARBOXYLASE EXPRESSION LEADS TO TRANSLOCATION AND ACTIVATION OF PROTEIN-KINASE CK2 IN-VIVO

Ornithine decarboxylase (ODC) is the key initial enzyme in the biosynt hesis of polyamines. Since polyamines have been shown to enhance prote in kinase CK2 activity in vitro, ODC was overexpressed to examine the role of polyamines in CK2 regulation in vivo. Infection of Balb/MK cel ls with an ODC retrovirus to elevate ODC and polyamine levels increase d overall protein phosphorylation as well as CK2 protein levels and en zyme activity in mimosine- or nocodazole- arrested cells. Immunofluore scence microscopy and enzyme analyses of subcellular fractions from OD C-overexpressing cells demonstrated translocation of CK2 from the cyto plasm to the nucleus with no apparent loss of cytoplasmic CK2 activity , suggesting polyamine activation of the remaining cytoplasmic enzyme. Similarly, K6/ODC transgenic mice exhibited higher ODC and CK2 enzyme activities than their normal littermates. ODC-immunostained cells in the transgenic skin also stained intensely for CK2 protein. Primary cu ltures of K6/ODC keratinocytes also exhibited increased ODC and CK2 en zyme activities compared with those from normal littermates. However, the addition of difluoromethylornithine, a specific ODC inhibitor, to the transgenic keratinocytes reduced both intracellular polyamine leve ls and CK2 enzyme activity, These results suggest that polyamines regu late the CK2 enzyme by affecting its cellular distribution as well as its enzyme activity and levels.