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Increased Activity of Chromatin-Bound Ribonucleic Acid Polymerase from Soybean Hypocotyl with Spermidine and High Ionic Strength

T. J. Guilfoyle and J. B. Hanson
Plant Physiology
Vol. 51, No. 6 (Jun., 1973), pp. 1022-1025
Stable URL: http://www.jstor.org/stable/4263264
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Increased Activity of Chromatin-Bound Ribonucleic Acid Polymerase from Soybean Hypocotyl with Spermidine and High Ionic Strength
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Abstract

Optimal activity of chromatin-bound RNA polymerase from soybeans is obtained with 1 mM Mn2+, but only when high ionic strength or polyamines are included in the medium. Such inclusion does not increase the Mg2+ activation of the polymerase, but it does lower the concentration needed for optimum activity from 10 mM to 1 mM. Mg2+ activation is inhibited by added Mn2+, and the inhibition is relieved by high ionic strength or spermidine. The RNA polymerase with either cation is almost entirely polymerase I at low and high ionic strength as evidenced by insensitivity to α-amanitin. Treatment of soybean seedlings with 2,4-dichlorophenoxyacetic acid does not change these characteristics; although the activity rises 3- to 4-fold. It is suggested that chromatin as prepared here may be a selected fraction enriched in polymerase I, which is activated by either Mg2+ or Mn2+, and that the Mn2+ inhibition of activity is due to a known reaction of Mn2+ with DNA which can be relieved by high ionic strength.

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