Synthesis of RNA in isolated polytene nuclei from salivary gland cells of Chironomus thummi |
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Authors: | R. Mähr J.C. Perriard M. Lezzi H.M. Eppenberger |
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Affiliation: | Institute for Cell Biology, Swiss Federal Institute of Technology, CH-8093 Zürich, Switzerland |
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Abstract: | The incorporation of [3H]UTP into RNA by isolated polytene salivary gland nuclei of Chironomus thummi was investigated under different incubation conditions; the labeled RNA fractions were characterized by electrophoresis. The results suggested that at two characteristic ionic conditions most of the RNA synthesized was the product of RNA polymerase I or RNA polymerase II as distinguished by their differential sensitivities to α-amanitin. Electrophoretical analysis of the RNA synthesized under conditions favouring polymerase I showed that this RNA population consisted mainly of four distinct molecular weight fractions within a range between 2.8 × 104 and 2.5 × 106. Under conditions favouring polymerase II two fractions were detected: one with a broad molecular weight distribution around 0.4 × 106 containing considerable amounts of poly(A)-bearing RNA molecules, and a second with a peak at a molecular weight of 2.8 × 104. |
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