Several examples of inhibition of the function of a ribozyme or RNA-pr
otein complex have shown that certain antibiotics can interact specifi
cally with RNA. There are, however, few examples of antibiotics that h
ave a positive, rather than a negative, effect on the function of an R
NA. We have found that micromolar concentrations of viomycin, a basic,
cyclic peptide antibiotic of the tuberactinomycin group, enhance the
cleavage of a ribozyme derived from Neurospora VS RNA. Viomycin decrea
ses by an order of magnitude the concentration of magnesium required f
or cleavage, It also stimulates an otherwise insignificant trans-cleav
age reaction by enhancing interactions between RNA molecules. The abil
ity of viomycin to enhance some RNA-mediated reactions but inhibit oth
ers, including translation and Group I intron splicing, demonstrates t
he potential for natural selection by small molecules during evolution
in the 'RNA world' and may have broader implications with respect to
ribozyme expression and activity in contemporary cells.