Alteratons in RNA synthesis in lymphotoxin-treated target cells.

Lymphotoxin, a cellular mediator produced in vitro by antigen- or mitogen-stimulated lymphocytes, is capable of lysing various types of cells. We have shown that highly purified lymphotoxin preparations both mediate cytolysis and stimulate RNA synthesis in target cells. When RNA extracts from lymphotoxin-treated cells were examined by means of sucrose density gradient centrifugation, we observed a general increase in RNA synthesis, accentuated in species larger than 28S. Analysis on oligo(dT)-cellulose columns revealed a relatively larger increase in adenine-rich m-RNA. In concordance with this finding, we observed a moderate increase in RNA polymerase I (nucleolar) activity and a striking increase in RNA polymerase II (nucleoplasmic) activity in isolated nuclei of lymphotoxin-treated target cells.