Larkin R M, Guilfoyle T J
Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
J Biol Chem. 1998 Mar 6;273(10):5631-7. doi: 10.1074/jbc.273.10.5631.
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.
克隆了一个拟南芥cDNA（AtRPB15.9），其编码的蛋白质与酵母RNA聚合酶II中的RPB4亚基相关。AtRPB15.9蛋白预测的分子量为15.9 kDa，明显小于酵母RBP4的25 kDa。在SDS-PAGE中，AtRPB15.9在拟南芥RNA聚合酶II中作为第七或第八大亚基迁移（即表观分子量为14 - 15 kDa），而RPB4在酵母RNA聚合酶II中作为第四大亚基迁移（即表观分子量为32 kDa）。与在温和变性条件下从RNA聚合酶II解离的酵母RPB4和RPB7不同，与RPB4和RPB7相关的植物亚基与该酶的结合更稳定。重组AtRPB15.9在体外与AtRPB19.5（即与酵母RPB7相关的亚基）形成稳定复合物，重组酵母RPB4和RPB7亚基也是如此。AtRPB15.9与酵母RPB7之间以及酵母RPB4与AtRPB19.5之间也形成了稳定的异二聚体。
