THE PLANT CELL, Vol 1, Issue 8 827-836, Copyright © 1989 by American Society of Plant Biologists
A Protein Kinase from Wheat Germ That Phosphorylates the Largest Subunit of RNA Polymerase II
T. J. Guilfoyle
Department of Biochemistry, University of Missouri, 117 Schweitzer Hall, Columbia, Missouri 65211
A protein kinase from wheat germ that phosphorylates the largest subunit of
RNA polymerase IIA has been partially purified and characterized. The
kinase has a native molecular weight of about 200 kilodaltons. This kinase
utilizes Mg2+ and ATP and transfers about 20 phosphates to the heptapeptide
repeats Pro-Thr-Ser-Pro-Ser-Tyr-Ser in the carboxyl-terminal domain of the
220-kilodalton subunit of soybean RNA polymerase II. This phosphorylation
results in a mobility shift of the 220-kilodalton subunits of a variety of
eukaryotic RNA polymerases to polypeptides ranging in size from greater
than 220 kilodaltons to 240 kilodaltons on sodium dodecyl
sulfate-polyacrylamide gels. The phosphorylation is highly specific to the
heptapeptide repeats since a degraded subunit polypeptide of 180
kilodaltons that lacks the heptapeptide repeats is poorly phosphorylated.
Synthetic heptapeptide repeat multimers inhibit the phosphorylation of the
220-kilodalton subunit.
