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Updated: Sep 15, 2026

Novel RNA-Binding Proteins Isolation by the RaPID Methodology
Published on: September 30, 2016
Two small subunits in Arabidopsis RNA polymerase II are related to yeast RPB4 and RPB7 and interact with one another
1Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
Abstract:
An Arabidopsis cDNA (AtRPB15.9) that encoded a protein related to the RPB4 subunit in yeast RNA polymerase II was cloned. The predicted molecular mass of 15.9 kDa for the AtRPB15.9 protein was significantly smaller than 25 kDa for yeast RBP4. In SDS-PAGE, AtRPB15.9 migrated as the seventh or eighth largest subunit (i.e. apparent molecular mass of 14-15 kDa) in Arabidopsis RNA polymerase II, whereas RPB4 migrates as the fourth largest subunit (i.e. apparent molecular mass of 32 kDa) in yeast RNA polymerase II. Unlike yeast RPB4 and RPB7, which dissociate from RNA polymerase II under mildly denaturing conditions, plant subunits related to RPB4 and RPB7 are more stably associated with the enzyme. Recombinant AtRPB15.9 formed stable complexes with AtRPB19.5 (i.e. a subunit related to yeast RPB7) in vitro as did recombinant yeast RPB4 and RPB7 subunits. Stable heterodimers were also formed between AtRPB15. 9 and yeast RPB7 and between yeast RPB4 and AtRPB19.5.
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