Cloning of cDNAs encoding Bombyx homologues of Cdc2 and Cdc2-related kinase from eggs

In diapausing eggs of the silkworm, Bombyx mori, embryonic cells are arrested at G₂ phase. The ability to undertake cell division is resumed in the course of dispause termination caused by such a treatment as acclimation to 5°C. As an initial trial to investigate the relationship between diapause end embryonic cell cycling, we have cloned and sequenced two Bombyx cDNAs encoding two distinct cdc2-related Ser/Thr protein kinases. One (Bm cdc2) encoded a 37.0 kDa protein which had all of the domains characteristic of other Cdc2 kinase. The other (Bcdrk) encoded a 45.1 kDa protein that was most similar to Drosophila and human cdc2-related protein kinases (Dcdrkprotein and PISSRLE kinase). Northern blot analysis was carried out to examine levels of Bm cdc2 end Bcdrk mRNA during embryogenesis of non-diapause eggs. The result demonstrated that the mRNA level of Bm cdc2 appeared to correspond to the activity of nuclear/cellular division in non-diapause eggs, and that the developmental profile in the level of Bcdrk mRNA was somewhat different from that of Bm cdc2 mRNA.