Inhibitory effects of acid polysaccharides from sea urchin embryos on RNA polymerase activity

Abstract

The present experiments were carried out in order to investigate the cytoplasmic inhibitors of RNA synthesis in vitro prepared from the sea urchin embryos, Anthocidaris crassispina or Hemicentrotus pulcherrimus. These inhibitors appeared to be acid polysaccharides. 1. 1. The inhibitory effect of the acid polysaccharides on in vitro RNA synthesis using Escherichia coli RNA polymerase or sea urchin RNA polymerase was essentially identical to that of authentic heparin which has been suggested to interact with E. coli RNA polymerase rather than template DNA molecules. The acid polysaccharides completely blocked the initiation of RNA synthesis in an in vitro system of low ionic strength. 2. 2. The interaction between RNA polymerase and acid polysaccharides seemed to be effected by ionic charges, as indicated by the results on the inhibitory effect of various polyanions and its variations under different ionic environments. 3. 3. Desulfation of either authentic acid polysaccharides, i.e., heparin and chondroitin sulfate, or of the acid polysaccharides prepared from intercellular substances markedly reduced their inhibitory activities of RNA synthesis in vitro. Heparin containing both N-sulfate and O-sulfate groups was a stronger inhibitor than chondroitin sulfate containing only O-sulfate groups. 4. 4. The results obtained so far are discussed in relation to differential repression of genic activities in the course of embryonic development.