Mithramycin inhibition of ribonucleic acid synthesis.

Abstract

Mithramycin, an antibiotic derived from an organism belonging to the genus Streptomyces, was studied in mouse ascites tumor and mouse liver by measuring its effect on the incorporation of phosphate-32P into RNA and DNA in vitro and in vivo . A marked inhibition of incorporation into the RNA of the tumor and liver was observed with no measurable effect upon incorporation of isotope into the DNA of the ascites tumor. The effect was similar to that of actinomycin D in time of onset, but mithramycin was observed to be only about 0.1 times as potent as actinomycin D in this respect.