Molecular Pharmacology, Vol 5, 219-226, Copyright © 1969 by the American Society for Pharmacology and Experimental Therapeutics

Activation of Genetic Transcription in Rat Liver Chromatin by 3-Methylcholanthrene

¹ Department of Pharmacology, Baylor University College of Medicine, Houston, Texas 77025

Previous studies had indicated that the administration of 3-methylcholanthrene to rats is attended by an increase in the "aggregate" RNA polymerase activity in rat liver. Chromatin has been isolated from the livers of both control and 3-methylcholanthrene-treated rats. The experimental chromatin did not differ from control material in RNA:DNA and histone to DNA ratios, ultraviolet absorption, or transition temperature. The efficacy of the chromatin as a template was determined in the Micrococcus lysodeikticus RNA polymerase system. The liver chromatin from 3-methylcholanthrene-treated rats proved to be a better template. Adrenalectomy did not affect this finding. The nearest neighbor frequency of the RNA elaborated on the chromatin template was also determined. The RNA product made in the presence of chromatin isolated from 3-methylcholanthrene-treated rats differed substantially from that made in the presence of control chromatin or rat liver DNA itself. These studies provide further evidence that the administration of the polycyclic hydrocarbon leads to an activation of a region(s) on the genome.