In this method or protocol nuclei isolated from cells expressing the gene of interest are incubated with radiolabeled UTP which is incorporated into nascent RNA transcripts by RNA polymerase molecules that were actively transcribing at the time the cells were harvested. Because very little denovo initiation of RNA synthesis occurs in isolated nuclei, transcription of the target gene can be measured by hybridizing the radiolabeled RNA to an excess of the target gene immobilized on a nitrocellulose or nylon

Protocol: Protocol Describing Transcriptional Run- On Assays