RBC-mediated microinjection of chromatin components into cultured mammalian cells.

Radiolabeled DNA fragments or nuclear proteins were encapsulated within human erythrocytes, and the erythrocytes were then fused with cultured mammalian cells using Sendai virus. Autoradiography revealed that 125I-labeled DNA fragments remained dispersed in the cytoplasm and disappeared with a half-life of 24 hours. In contrast, the nuclear proteins, HMG1, HMG2, HMG17 and histone H1, rapidly localized within HeLa nuclei and exhibited half lives greater than 80 hours. Several biochemical criteria indicate that the association of the injected nuclear proteins with chromatin faithfully mimics the behavior of their endogenous counterparts.