[Effect of sphingomyelin on RNA-polymerase activity in the cell nucleus of normal and regenerating rat liver].

Using a model of regenerating rat liver, it was shown that the activities of RNA polymerases I and II, and the ratio of free to template engaged form of the enzyme are correlated with the changes in the contents of sphingomyelin in chromatin isolated from cell nuclei of hepatectomized animals. Injections of sphingomyelin to intact and hepatectomized animals in doses increasing its contents in chromatin, stimulate the activity of RNA polymerases I and II and increase the ratio of free to engaged form of the enzyme. Addition of sphingomyelin as a micellar suspension to heterochromatin in vitro facilitates RNA polymerase binding to the template. Removal of sphingomyelin from the intranuclear structures by its degradation with sphingomyelinase results in a loss of activities of both RNA polymerases. It is assumed that sphingomyelin plays a role in the transcriptional activity by changing the structure of the template and that of the enzymes.