Healy J M, Menges M, Doonan J H, Murray J A
Institute of Biotechnology, University of Cambridge, United Kingdom.
J Biol Chem. 2001 Mar 9;276(10):7041-7. doi: 10.1074/jbc.M009074200. Epub 2000 Nov 28.
D-type cyclins (CycD) play key roles in linking the Arabidopsis cell cycle to extracellular and developmental signals, but little is known of their regulation at the post-transcriptional level or of their cyclin-dependent kinase (CDK) partners. Using new antisera to CycD2 and CycD3, we demonstrate that the CDK partner of these Arabidopsis cyclins is the PSTAIRE-containing CDK Cdc2a. Previous analysis has shown that transcript levels of CycD2 and CycD3 are regulated in response to sucrose levels and that both their mRNA levels and kinase activity are induced with different kinetics during the G(1) phase of cells reentering the division cycle from quiescence. Here we analyze the protein levels and kinase activity of CycD2 and CycD3. We show that CycD3 protein and kinase activity parallel the abundance of its mRNA and that CycD3 protein is rapidly lost from cells in stationary phase or following sucrose removal. In contrast to both CycD3 and the regulation of its own mRNA levels, CycD2 protein is present at constant levels. CycD2 kinase activity is regulated by sequestration of CycD2 protein in a form inaccessible to immunoprecipitation and probably not complexed to Cdc2a.
D型细胞周期蛋白（CycD）在将拟南芥细胞周期与细胞外信号及发育信号联系起来的过程中发挥着关键作用，但对于它们在转录后水平的调控以及它们的细胞周期蛋白依赖性激酶（CDK）伙伴却知之甚少。利用针对CycD2和CycD3的新抗血清，我们证明这些拟南芥细胞周期蛋白的CDK伙伴是含有PSTAIRE的CDK Cdc2a。先前的分析表明，CycD2和CycD3的转录水平会根据蔗糖水平进行调控，并且在从静止状态重新进入分裂周期的细胞的G(1)期，它们的mRNA水平和激酶活性均以不同的动力学被诱导。在此，我们分析了CycD2和CycD3的蛋白质水平及激酶活性。我们发现CycD3蛋白及其激酶活性与其mRNA丰度平行，并且CycD3蛋白在静止期细胞或蔗糖去除后会迅速从细胞中消失。与CycD3及其自身mRNA水平的调控不同，CycD2蛋白以恒定水平存在。CycD2激酶活性是通过将CycD2蛋白隔离成一种免疫沉淀无法触及的形式来调控的，这种形式可能未与Cdc2a形成复合物。
