Stabilization of heterogeneous nuclear RNA by intercalating drugs

The effect of the intercalating drugs proflavine, ethidium and daunomycin on the rate of degradation of 14C-labeled heterogeneous nuclear RNA (HnRNA) in KB cells was studied. All three drugs decreased the rate of degradation of 14C-HnRNA to acid soluble products. The most striking effect was produced by proflavine which promptly and completely stabilized 14C-HnRNA against degradation. Ethidium also produced complete stabilization after a delay of 30 to 60 min. Daunomycin decreased the rate of 14C-HnRNA degradation but did not alter the fraction of 14C-HnRNA which was ultimately degraded. The results are consistent with the view that base-paired sequences are present in HnRNA in vivo and play a role in the processing of HnRNA.