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  • Title: [DNA-dependent RNA-polymerase from loach embryos. Changes in the activity of forms I and II of the enzyme in the course of development].
    Author: Ekizashvili VK, Gauze LH, Kafiani KA.
    Journal: Biokhimiia; 1980 Jul; 45(7):1233-44. PubMed ID: 7194120.
    Abstract:
    The changes in the activity of form I and II DNA-dependent RNA-polymerases from the nuclei and cytoplasm in early embryos of loach (Misgurnus fossilis) were studied. Both forms of the polymerase activity were found in the nuclei at all stages of development including the morula stage, when the nuclear synthesis of RNA in vivo is practically absent. During an abrupt increase of transcription (the blastula stage), the total RNA polymerase activity of the nuclei is increased 10-15 fold per nucleus and more than 300-fold as calculated per total embryo nuclei. The RNA-polymerase activity in the lysate of whole embryos showed little change. The cytoplasm at the morula stage contained RNA-polymerases of both forms; in the course of ontogenesis from II and, later, form I of the RNA-polymerase activity disappeared from the cytoplasm. In the nuclei the activity of form II and then form I of RNA-polymerase is increased. It is assumed that the increase of the content of active polymerase molecules in the nuclei during rapid multiplication of the nuclei and the activation of nuclear RNA synthesis in early embryogenesis is due to a transition of RNA-polymerases accumulated in the egg cytoplasm into the nuclei. At the gastrula stage, when an intense synthesis of rRNA occurs in vivo, the activity ratio of forms I and II of the enzyme is sharply changed in favour of form I. Moreover, a positive correlation is observed between the increase in the rate of synthesis of a definite class of RNA (D-DNA- or rRNA) and the presence of the corresponding enzyme form in the nuclei in a state available for activation by exogenous DNA.
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