Transcription inhibition by Rh(phi)2(phen)3+

Abstract

Rh(phi)₂(phen)³⁺ (phi = 9,10-phenanthrenequinone diimine, phen = 1,10-phenanthroline) increases the melting temperature (ΔT_m) of a 15-mer duplex DNA by 21 °C and it is able to inhibit transcription in vitro; the concentration ratio of Rh(phi)₂(phen)³⁺ relative to DNA bases of the template required to inhibit the RNA transcribed by 50%, R_inh⁵⁰, was found to be 0.13; in contrast, Rh(phen)₂(phi)³⁺, which also possesses the intercalating phi ligand, exhibits only a +7 °C shift in T_m and R_inh⁵⁰ = 4.5; Rh(phen)₃³⁺, RhCl₃, and ethidium bromide result in negligible or small ΔT_m and exhibit R_inh⁵⁰ values that range from 4.8 to 12.5; these results suggest that the intercalation of the phi ligand between the DNA bases and electrostatic binding are not the only means of duplex stabilization by these complexes.