Regulation of thymidine phosphorylation in nucleate and anucleate cells ofAcetabularia

Abstract
The rate of thymidine phosphorylation was estimated in Acetabularia mediterranea by measuring the in vivo incorporation of [6-3H]thymidine into dTTP. Young cells incorporated little thymidine within 10 min. During growth of the stalk the incorporation rate increased slowly. When caps formed, no further increase was observed. But as the caps matured and the stalk became yellow-green, a steep increase in incorporation took place. This increase was also demonstrated in cells enucleated at the beginning of cap formation. Actinomycin D (3 mg/ml), when added 2 days prior to the critical stage, did not inhibit the increase, but puromycin (50 mg/l) did.