A factor in sea urchin eggs inhibits transcription in isolated nuclei by sea urchin RNA polymerase III

Abstract

Isolated nuclei from sea urchin [Lytechinus variegatus and Strongylocentrotus purpuratus] embryos synthesize RNA at a rate comparable to other animal cell nuclei. All 3 RNA polymerases are active as judged by .alpha.-amanitin sensitivity and hybridization to specific cloned DNA. Extracts were prepared from sea urchin eggs and embryos by extraction with 0.35 M KCl. None of the crude extracts had a large effect on total RNA synthesis. Extracts from sea urchin eggs inhibited RNA polymerase III activity in nuclei from blastula and gastrula embryos. There was no effect on the synthesis of rRNA by RNA polymerase I or on the synthesis of 2 RNA polymerase II products, histone mRNA and the sea urchin analog of U1 RNA. The inhibitor is present in 2 different species of sea urchin and was .apprx. 50-fold purified by DEAE cellulose and hydroxylapatite chromatography. The inhibitor is not present in extracts prepared from sea urchin blastula embryos.