Mechanism of the inhibition by RNA of the RNA polymerases of Histoplasma capsulatum.

4 S RNA isolated from the dimorphic fungus Histoplasma capsulatum inhibited the DNA-dependent RNA polymerase activity of the yeast phase of this fungus. Inhibition was specific for initiation, and resulted from binding of the RNA to the enzyme. Among a variety of synthetic polynucleotides tested, only poly(G) and oligo(dG) were effective inhibitors, suggesting a role for guanines or guanine-rich sequences of RNA in the inhibition reaction.