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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 7408

Liren Tang, Sina M. Adl, and James D. Berger; A CDC2-Related Kinase is Associated with Macronuclear DNA Synthesis in Paramecium tetraurelia. J.Eukaryot.Microbiol. 44(3):269-275, 1997

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Cell division in higher eukaryotes is mainly controlled by CDK (serine/threonine) protein kinases and by other components of these kinase complexes. Previously, we showed homologous kinases also occur in the ciliate Paramecium tetraurelia. In this report, a polyclonal antibody was produced against a GST fusion protein which contained the N-terminal third of the previously isolated CDC2PTA protein. It recognized a 36 kDa polypeptide on western blots and did not cross-react with the related 34 kDa polypeptide. This 36 kDa polypeptide showed no affinity for yeast P13(suc1) protein. The CDC2PTA level was invariant throughout the cell cycle and decreased slightly when cells entered stationary phase. Indirect immunofluorescence showed CDC2PTA localized in the macronucleus, but no in micronuclei. Native CDC2PTA was immunoprecipitated and the kinase activity was assayed using histone H1 as substrate in elutriation synchronized samples. The kinase activity was high during the early stages of the cell cycle and reached a peak at 2.5 hr after elutriation, which corresponds to the time of initiation of macronuclear DNA synthesis. This suggests CDC2PTA kinase may be associated with the regulation of macronuclear DNA synthesis. These results allow us to draw concrete comparisons for the first time between the role of CDK in ciliates and higher eukaryotes.