Nucleo-cytoplasmic interactions in the regulation of thymidine phosphorylation inAcetabularia

Abstract

The activity of dT kinase (EC. 2. 7. 1. 75) was estimated during the development of nucleate and anucleate cells inAcetabularia. Enzyme activity increases as the cap attains its maximum diameter (Bannwarth & Schweiger 1975). Regulation of the dT kinase activity is observed even in the absence of the cell nucleus. Twelve to fifteen days after enucleation dT kinase activity increase sharply as the cap reaches its maximum diameter and decreases 5 days later. The increase is inhibited by puromycin, chloramphenicol, rifampicin and ethidium bromide but not by cycloheximide. These findings indicate that protein synthesis on 70S organelle ribosomes is involved in the regulation of the dT kinase. Since activities of mixtures from low activity cell extracts and from high activity cell extracts are additive, it is concluded that the regulation is not mediated through an activator protein but rather throughde novosynthesis of the enzyme protein.