Antibody against a stimulatory factor of RNA polymerase II inhibits nuclear RNA synthesis

Abstract

THE mechanisms by which eukaryotic genes are differentially activated are mostly unknown. However, the most fundamental process of gene expression is thought to be transcription by RNA polymerase II, and thus the regulation of RNA synthesis by this enzyme is one of the important points of study of eukaryotic gene expression. It is generally believed that structural modification of chromatin governs the transcriptability of the template1, and consequently studies have been carried out on the activity of chromatin2–4. Recently, another possibility has been considered, that various regulatory proteins may be involved in the process of transcription and regulate the gene expression5. However, although there are many reports of proteins stimulating the activity of RNA polymerase II in vitro6–11, no conclusive evidence has yet been obtained to show that these proteins are, in fact, functioning in the process of nuclear RNA synthesis. We have purified a protein from Ehrlich ascites tumour cells that specifically stimulates the activity of RNA polymerase II on homologous DNA12. Named S-II, this is a basic protein with a molecular weight of 40,500. We report here that an antibody against S-II markedly inhibits RNA synthesis in isolated nuclei, but that it does not affect the activity of purified RNA polymerase II. These findings suggest that the processes of RNA synthesis in isolated nuclei and with purified RNA polymerase II and deproteinised DNA are basically different, and that S-II has an essential role in nuclear RNA synthesis.