In vivo and in vitro effect of α-amanitin on preimplantation mouse embryo RNA polymerase

Abstract

THE effects of various metabolic inhibitors, including actinomycin D, puromycin, cycloheximide, mitomycin C, and fluorophenylalanine, on preimplantation mouse embryos have been previously studied^1–6, to investigate when RNA synthesis begins in preimplantation embryos and what types of RNA are synthesised during the various stages of development. Monesi and Salfi³ originally reported that there was no appreciable overall RNA synthesis until the morula stage. Ellem and Gwatkin⁷ also found no detectable RNA synthesis at the two-cell stage of development. Recently, using more sensitive techniques, RNA synthesis has been detected as early as the two-cell stage of development^8–10. We assumed that since RNA synthesis occurs in preimplantation mouse embryos, the enzyme, DNA-dependent RNA polymerase, must be active. We report here the results of in vivo and in vitro experiments intended to characterise more fully the RNA polymerase present in preimplantation mouse embryos. We used the mushroom toxin, α-amanitin, to determine which forms of RNA polymerase are active and the relative amounts of each form which are present in preimplantation mouse embryos.