Studies on the template activity of 'isolated' Xenopus erythrocyte nuclei. II. The effects of cytoplasmic extracts.

The effects of exposing nuclei isolated from Xenopus erythrocytes to cytoplasmic extracts prepared from various sources on their template activity are described. The cytoplasm of rat liver cells and the immature blood cells of Xenopus contain factors which stimulate RNA synthesis in these essentially inactive nuclei, whereas the cytoplasm of many other cells does not yield such factors. The active factors in rat liver cytoplasmic extracts appear to be proteins of molecular weight about 40000 Daltons. The implications of these results for genetic control in eukaryotes are discussed.