Specific Inhibition by Rifampicin of Transcription in Human Lymphocytes Stimulated by Phytohemagglutinin

Rifampicin, a semisynthetic antibiotic, is known to inhibit the bacterial DNA-dependent RNA polymerase (1), the growth of some animal viruses (2), and the focus formation induced by oncogenic viruses (3, 4). While certain derivatives of rifampicin can inhibit the RNA-dependent DNA polymerase activity of oncogenic viruses, and a similar activity found in normal and virus-transformed cells (5-7), rifampicin itself, when tested in vitro, has no effect on the mammalian DNAdependent RNA polymerases (I) . Nevertheless, toxicity of the drug for some cell lines has been reported (8) . Recently, rifampicin has been shown to