Nilemycin, an intercalating agent for deoxyribonucleic acid.
1. Nilemycin (NM) is found to exert an inhibitory effect on the mouse tumor Sarcoma 180 near toxic doses but not with Leukemia 1210. 2. In Yoshida rat sarcoma cells NM inhibits cellular de novo nucleic acid synthesis and protein to a much lesser extent. 3. More than 50% inhibition by NM to de novo synthesis of RNA, in a system using calf thymus DNA as a template, could be observed. 4. Suitable levels of NM reduce the S values of DNA. 5. The antibiotic induced metachromatic changes in the u.v. spectrum of DNA solutions. 6. NM markedly inhibited the polynucleotide ligase repairing action on DNase-1-nicked DNA. 7. It is presumed that NM intercalates nicked DNA into such a configuration that the reactive sites of the polynucleotides are inaccessible to the ligase activities.