Characteristics of the binding of RNA polymerase to template in mouse liver nuclei

In whole nuclei isolated from mouse liver, the reaction of free RNA polymerase with the artificial template, poly (dA-dT), is temperature dependent. At assay temperatures below 37 degrees C, the amount of free RNA polymerase (RNA polymerase not inhibited by actinomycin D) which can be measured is substantially reduced. However, if the nuclei are preincubated at 37 degrees C in the presence of template and then assayed at lower temperatures, substantial amounts of enzyme activity can be measured. The active complex (enzyme bound to template) is resistant to inactivation by heparin. This evidence is consistent with a two-stage model for binding of eukaryotic RNA polymerase to template similar to the binding of prokaryotic RNA polymerase to template.