Serizawa H, Conaway R C, Conaway J W
Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City 73104.
Proc Natl Acad Sci U S A. 1992 Aug 15;89(16):7476-80. doi: 10.1073/pnas.89.16.7476.
We previously purified RNA polymerase II transcription factor delta from rat liver and found that it has an associated DNA-dependent ATPase (dATPase) activity. In this report, we show that delta is also closely associated with a protein kinase activity that catalyzes phosphorylation of the largest subunit of RNA polymerase II. Kinase activity copurifies with transcription and DNA-dependent ATPase (dATPase) activities when delta is analyzed by anion- and cation-exchange HPLC as well as by sucrose gradient sedimentation, arguing that delta possesses all three activities. Phosphorylation of the largest subunits of both rat and yeast RNA polymerase II is stimulated by DNA, whereas phosphorylation of a synthetic peptide containing multiple copies of the carboxyl-terminal heptapeptide repeat is not. Although both ATP and GTP appear to function as phosphate donors, GTP is utilized less than 10% as well as ATP. These findings suggest that delta may exert its action in transcription at least in part through a mechanism involving phosphorylation of the largest subunit of RNA polymerase II.
我们之前从大鼠肝脏中纯化了RNA聚合酶II转录因子δ，并发现它具有相关的依赖DNA的ATP酶（dATP酶）活性。在本报告中，我们表明δ还与一种蛋白激酶活性密切相关，该蛋白激酶活性催化RNA聚合酶II最大亚基的磷酸化。当通过阴离子和阳离子交换高效液相色谱以及蔗糖梯度沉降分析δ时，激酶活性与转录和依赖DNA的ATP酶（dATP酶）活性共纯化，这表明δ具有所有这三种活性。大鼠和酵母RNA聚合酶II最大亚基的磷酸化受到DNA的刺激，而含有多个羧基末端七肽重复序列拷贝的合成肽的磷酸化则不受刺激。尽管ATP和GTP似乎都作为磷酸供体起作用，但GTP的利用率不到ATP的10%。这些发现表明，δ可能至少部分地通过涉及RNA聚合酶II最大亚基磷酸化的机制在转录中发挥作用。
