Shimotohno Akie, Ohno Ryoko, Bisova Katerina, Sakaguchi Norihiro, Huang Jirong, Koncz Csaba, Uchimiya Hirofumi, Umeda Masaaki
Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-0032, Japan.
Plant J. 2006 Sep;47(5):701-10. doi: 10.1111/j.1365-313X.2006.02820.x. Epub 2006 Jul 11.
For the full activation of cyclin-dependent kinases (CDKs), not only cyclin binding but also phosphorylation of a threonine (Thr) residue within the T-loop is required. This phosphorylation is catalyzed by CDK-activating kinases (CAKs). In Arabidopsis three D-type CDK genes (CDKD;1-CDKD;3) encode vertebrate-type CAK orthologues, of which CDKD;2 exhibits high phosphorylation activity towards the carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II. Here, we show that CDKD;2 forms a stable complex with cyclin H and is downregulated by the phosphorylation of the ATP-binding site by WEE1 kinase. A knockout mutant of CDKD;3, which has a higher CDK kinase activity, displayed no defect in plant development. Instead, another type of CAK - CDKF;1 - exhibited significant activity towards CDKA;1 in Arabidopsis root protoplasts, and the activity was dependent on the T-loop phosphorylation of CDKF;1. We propose that two distinct types of CAK, namely CDKF;1 and CDKD;2, play a major role in CDK and CTD phosphorylation, respectively, in Arabidopsis.
为了使细胞周期蛋白依赖性激酶（CDK）完全激活，不仅需要细胞周期蛋白结合，还需要T环内苏氨酸（Thr）残基的磷酸化。这种磷酸化由CDK激活激酶（CAK）催化。在拟南芥中，三个D型CDK基因（CDKD;1 - CDKD;3）编码脊椎动物型CAK同源物，其中CDKD;2对RNA聚合酶II最大亚基的羧基末端结构域（CTD）表现出高磷酸化活性。在这里，我们表明CDKD;2与细胞周期蛋白H形成稳定复合物，并被WEE1激酶对ATP结合位点的磷酸化下调。具有较高CDK激酶活性的CDKD;3敲除突变体在植物发育中没有缺陷。相反，另一种类型的CAK - CDKF;1 - 在拟南芥根原生质体中对CDKA;1表现出显著活性，并且该活性依赖于CDKF;1的T环磷酸化。我们提出，两种不同类型的CAK，即CDKF;1和CDKD;2，分别在拟南芥的CDK和CTD磷酸化中起主要作用。
