Abstract
Induction of DNA synthesis in chick erythrocytes after fusion with BHK cells was compared in the early, middle and late S phase. In hetero-karyons fused with early S phase cells, more than 55 % showed the induction of DNA synthesis in the chick nuclei even in the presence of cyclo-heximide (1 μg/ml). However, in heterokaryons fused with late S phase cells, less than 20 % showed the induction of DNA synthesis in the chick nuclei in the presence of the same amount of cycloheximide. These results suggest that the induction of DNA synthesis in chick nuclei in the early S phase does not depend on protein synthesis because of the accumulation of inducers and because in the late S phase protein synthesis is necessary for the induction of DNA synthesis in chcik nuclei.
