Nucleic acid polymerizing enzymes in developing Strongylocentrotus franciscanus embryos

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Abstract
DNA-dependent RNA polymerase, DNA-dependent DNA polymerase, and terminal riboadenylate transferase (TRT) activities were measured after DEAE-Sephadex chromatography of whole cell extracts prepared from eggs and staged embryos of the urchin S. franciscanus. Activity of each of these 3 polymerase classes is present in the egg, and the total activity per embryo was constant throughout embryogenesis to the pluteus stage (.apprx. 1000 cells). The egg seemed to contain sufficient DNA polymerase, RNA polymerase and TRT for embryogenesis. The increases in the synthesis of DNA, RNA and polyadenylated RNA tracts observed after fertilization must be due to the activation of the pre-existing egg enzymes. Separation of the egg into nucleate and anucleate halves demonstrated that RNA polymerases were not restricted to the egg nucleus. During development the enzymes became progressively more associated with the cell nucleus. The egg extracts contained low activities (.apprx. 6% total) of RNA polymerase II as measured by sensitivity to .alpha.-amanitin; this was confirmed by resolution of RNA polymerase forms I, II and III by gradient sievorptive elution on DEAE-Sephadex. Later stage embryos contained more nearly equal activities of RNA polymerase I, II and III, although the total RNA polymerase activity per embryo was not changed. Additionally, 2 chromatographically distinct species of RNA polymerase III were detected, 1 of which was observed only in later stages. Interconversion of enzymes via addition of new subunits or coordinate synthesis and loss of enzyme species must occur.

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