Induction of Oligo-2',5'-adenylate Synthetase in Human Lymphoid Cells Treated with 5-Azacytosine and 5-Iododeoxyuridine

Abstract

Oligo-2',5'-adenylate synthetase activity was investigated in several human lymphoblastoid cell lines of B cell origin treated with reagents having effects on gene expression, 5-azacytosine (5AZct), 5-azacytidine (5AZcd) and 5-iodo-2'-deoxyuridine (IUdR). Enzyme activity did not increase in cells treated with 5AZcd, but the other reagents induced significant levels of activity. Interferon (IFN) activity was not detected in culture fluids of cells treated with 5AZcd or 5AZct. On the other hand, treatment of cells with IUdR led to the production of 5 to 10 units/ml IFN by NC-37 and Raji cells, but not by other human B cell lines. Enzyme induction by IUdR occurred in IFN-producing cells, NC-37 and Raji, exposed to anti-IFN-alpha sera and also in IFN-non-producing human B cells. The effect of 5AZct on enzyme induction was observed only after cultivation of cells for more than 1 month. This compound could not induce enzyme activity in Epstein-Barr virus (EBV)-negative cells, BJAB, but only in the EBV-positive cell lines NC-37 and Raji. In contrast, treatment of cells with IUdR for only 3 days induced the enzyme in all human lymphoblastoid cell lines of B cell origin except P3HR-1, but not in other human cell lines, FL, HeLa and K562. Oligo-2',5'-adenylate synthetase activity in P3HR-1 cells, which produce EBV particles, was hardly affected by IUdR or IFN treatment.