DNA‐Dependent RNA Polymerase C from Xenopus laevis Ovaries Ability to Transcribe Intact Double‐Stranded DNA

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Abstract
DNA-dependent RNA polymerase C, partially purified from Xenopus laevis ovaries, has been resolved by DEAE-Sephadex chromatography in 2 forms, eluting at 0.2 M and 0.3 M ammonium sulfate, respectively. Both are sensitive to high concentrations of .alpha.-amanitine (200 .mu.g/ml). Their ionic strength dependence and divalent cation requirements are indistinguishable. Quantitatively, RNA polymerase C represents the major form of RNA polymerase activity solubilized from the ovaries. Both RNA polymerases C are able to transcribe efficiently either high molecular weight Xenopus DNA or intact adenovirus DNA, as compared to nicked DNA. In contrast, RNA polymerase A has little activity on an intact DNA template. The salt dependence of the RNA polymerases C activity is different on the 2 kinds of template. Nicked DNA is efficiently transcribed up to a salt concentration of 100 mM ammonium sulfate. On intact DNA, optimal transcription is obtained at 40 mM ammonium sulfate and is inhibited by higher salt concentrations.