THE CASEIN KINASE 1-ALPHA GENE OF DROSOPHILA-MELANOGASTER IS DEVELOPMENTALLY-REGULATED AND THE KINASE-ACTIVITY OF THE PROTEIN-INDUCED BY DNA-DAMAGE

We report the molecular cloning and characterisation of the first CK1( casein kinase) gene of Drosophila melanogaster (dmCK1). The protein se quence (DMCK1) shares significant homology with other mammalian CK1 pr otein kinases of the a sub-class. The dmCK1 gene is expressed only in adult females and during early embryonic development as a single trans cript. Western blot analysis of total protein extracts of different st ages of development show that the gene product is likewise present dur ing early embryogenesis and in adult females. Kinase activity studies show that DMCK1 is active when in vitro translated but inactive when i mmunoprecipitated from total early embryo extracts. However, after dep hosphorylation treatment the immunoprecipitates show high kinase activ ity. More significantly, DMCK1 kinase activity present in the immunopr ecipitates can be specifically activated by gamma-irradiation of early embryos. Also, when DMCK1 is immunoprecipitated after irradiation it appears to undergo phosphorylation. Immunolocalization of DMCK1 in ear ly embryos shows that the protein is predominantly cytoplasmic but aft er irradiation there is a significant relocalization to the interphase nucleus. The results suggest a possible requirement of the Drosophila CK1 alpha for mechanisms associated with DNA repair during early embr yogenesis.