Detection of Human and Chick Nuclear Antigens in Nuclei of Chick Erythrocytes during Reactivation in Heterokaryons with HeLa Cells

Inactive nuclei of chick erythrocyte resume RNA synthesis and increase in volume and dry mass in heterokaryons made by virus-induced fusion of human tumor cells (HeLa) with chick erythrocytes. Nuclear growth is due primarily to migration of human macromolecules into the chick nucleus. Human nucleoplasmic antigens were detected in the nucleoplasm and human nucleolar antigens were detected in the nucleoli of reactivated chick erythrocyte nuclei. After some time, chick-specific nucleolar antigens appear in the nucleoli of both the reactivated chick nuclei and the HeLa cellnuclei. The results suggest that human nuclear proteins play an important part in the reactivation of the chick genome.