Diverse phosphoregulatory mechanisms controlling cyclin-dependent kinase-activating kinases in Arabidopsis
Diverse phosphoregulatory mechanisms controlling cyclin-dependent kinase-activating kinases in Arabidopsis
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DOI：
10.1111/j.1365-313x.2006.02820.x
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发表时间：
2006-09-01
期刊：
影响因子：
7.2
通讯作者：
Umeda, Masaaki
中科院分区：
文献类型：
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作者：
Shimotohno, Akie;Ohno, Ryoko;Umeda, Masaaki
对于细胞周期蛋白依赖性激酶（CDK）的完全激活，不仅需要细胞周期蛋白结合，而且需要T环内的苏氨酸（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直向同源物，其中CDKD;2对RNA聚合酶II的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形成一个稳定的复合物与细胞周期蛋白H和下调磷酸化的ATP结合位点的WEE 1激酶。CDKD;3基因敲除突变体具有较高的CDK激酶活性，在植物发育中没有表现出缺陷。相反，另一种类型的CAK - CDKF;1 -在拟南芥根原生质体中表现出对CDKA;1的显著活性，并且该活性依赖于CDKF;1的T环磷酸化。我们建议，两种不同类型的CAK，即CDKF;1和CDKD;2，发挥主要作用，分别在CDK和CTD磷酸化，在拟南芥。
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.