Actinomycin D in low concentrations binds uniformly to human chromosomes

The binding of actinomycin D (actD) to fixed human metaphase chromosomes was studied by using autoradiography with [3H]actD and indirect immunofluorescence with a specific anti-actD antibody. At concentrations of 0.01 and 0.1 micrograms/ml there was a uniform distribution of drug along the chromosomes as observed by both methods. This is the first study to date characterizing actD binding at such low concentrations to human chromosomes. Since actD intercalates into the DNA helix with GC specificity, our observations indicate that detectable differences in base composition along the lengths of human chromosomes are minimal.