Plant DNA-dependent RNA polymerases: subunit structures and enzymatic properties of the class II enzymes from quiescent and proliferating tissues

Class II DNA-dependent RNA polymerases were purified from soybean tissues of different physiological states: (1) from seed embryo tissue, representative of a quiescent, low metabolic state and (2) from auxin-treated hypocotyl tissue, representative of a highly proliferative and metabolically active state. Dodecyl sulfate, polyacrylamide gel electrophoresis indicates that RNA polymerase II from embryonic tissue consists largely (90-95%) of the form IIA enzyme, the largest subunit having a molecular weight of 215 000. RNA polymerase II from hypocotyl tissue is exclusively a form IIB enzyme, the largest subunit having a molecular weight of 180 000. Polypeptides common to RNA polymerases IIA and IIB have the following molecular weights: 138 000; 42 000; 27 000; 22 000; 19 000; 17 600; 17 000; 16 200; 16 100; and 14 000. Peptide mapping in the presence of dodecyl sulfate suggests that the 215 000 and 180 000 subunits possess similar peptide fragments. Plant embryo tissues do not contain protease activity capable of cleaving the 215 000 subunit to the 180 000 subunit, but proliferating plant tissues do contain such an activity. Mixing experiments indicate that appreciable amounts of RNA polymerase IIB are not being artifactually produced during protein purification.     

The subunit structures of soluble and chromatin-bound RNA polymerase II from soybean

DNA-dependent RNA polymerase II is present in two forms, IIa and IIb, in germinating soybean. Form IIa is the dominant form of the enzyme in ungerminated embryos and appears to be a soluble enzyme. Form IIb increases in amount as germination progresses and is tightly bound to the chromatin template. The subunit structures of soybean RNA polymerases IIa and IIb are identical except for the molecular weights of their largest subunits which are 200,000 daltons and 170,000 daltons for IIa and IIb, respectively. The enzymes have seven common subunits: 142,000, 42,000, 26,000, 20,000, 16,000, 15,000, and 14,000 daltons.     

DNA-dependent RNA polymerases from Drosophila melanogaster adults: Isolation and partial characterization

In preparation for the isolation and biochemical characterization of putative RNA polymerase mutants, DNA-dependent RNA polymerases of Drosophila melanogaster adults were isolated and partially characterized. Approximately 70% of the female adult RNA polymerase is located in ovaries. Multiple forms of ovarian RNA polymerases I and II are separable by DEAE-Sephadex chromatography. The two forms of RNA polymerase II differ in ammonium sulfate optima. RNA polymerase IIA is more active with double-stranded DNA as template, whereas RNA polymerase IIB transcribes single-stranded DNA most efficiently. Rechromatography of RNA polymerase IIA on DEAE-Sephadex results in the loss of ability of this form to transcribed double-stranded DNA most efficiently. Ovariectomized carcasses have two forms of RNA polymerase I and one form of RNA polymerase II and each transcribes single-stranded DNA most efficiently. As judged by gel filtration chromatography, female adult extracts have forms of RNA polymerase II that differ in molecular weight and template preference.Supported by Grants GM23456 from the NIH and 11259 from the City University Research Foundation.