Stimulation of transcription of mouse kidney chromatin by sulfated polysaccharides

The sulfated polysaccharides polydextran sulfate (PDS) and heparin stimulate in vitro transcription of mouse kidney chromatin by E. coli RNA polymerase by about 100 and 40 fold respectively. Heparin which has been N-desulfated and N-acetylated stimulates only 13 fold. Chondroitin sulfate B and heparitin sulfate do not stimulate transcription under similar conditions. PDS inhibits transcription of deproteinized chromatin. Therefore, the stimulation with chromatin is due to interaction with the chromatin and not the polymerase. Polydextran sulfate has no effect on the size of the RNA that is made either under conditions in which the enzyme can reinitiate or under conditions in which reinitiation is blocked. If reinitiation of the enzyme is blocked, the time required to complete the synthesis of the RNA is the same whether or not the enzyme is stimulated by PDS. These observations indicate that sulfated polysaccharides stimulate transcription by making available new RNA polymerase binding sites on the chromatin.