Sorrell D A, Menges M, Healy J M, Deveaux Y, Amano C, Su Y, Nakagami H, Shinmyo A, Doonan J H, Sekine M, Murray J A
Institute of Biotechnology, University of Cambridge, Cambridge CB2 1QT, United Kingdom.
Plant Physiol. 2001 Jul;126(3):1214-23. doi: 10.1104/pp.126.3.1214.
Plants possess two major classes of cyclin-dependent kinases (CDK) with cyclin-binding motifs PSTAIRE (CDK-a) and PPTA/TLRE (CDK-b). Tobacco (Nicotiana tabacum L. cv Bright Yellow-2) cells are the most highly synchronizable plant culture, but no detailed analysis of CDK activities has been reported in this system. Here we describe isolation of new PPTALRE CDKs (Nicta;CdkB1) from Bright Yellow-2 cells and present detailed analysis of the mRNA, protein and kinase activity levels of CdkB1, and the PSTAIRE CDKA during the growth and cell cycles. CdkA and CdkB1 transcripts are more abundant in exponential than in stationary phase cells, but the two genes show strikingly different regulation during the cell cycle. CdkA mRNA and protein accumulate during G1 in cells re-entering the cell cycle, and immunoprecipitated histone H1 kinase activity increases at the G1/S boundary. Aphidicolin synchronized cells show the highest CDKA-associated histone H1 kinase activity during S-G2 phases, although CdkA mRNA and protein levels are not significantly regulated. In contrast, CdkB1 transcripts are present at very low levels until S phase and CDKB1 protein and kinase activity is almost undetectable in G1. CdkB1 mRNA accumulates through S until M phase and its associated kinase activity peaks at the G2/M boundary, confirming that transcription of PPTALRE CDKs is cell cycle regulated. We suggest that CDKA kinase activity likely plays roles at the G1/S phase boundary, during S phase, and at the G2/M phase transition, and that CDKB1 kinase activity is present only at G2/M.
植物拥有两类主要的细胞周期蛋白依赖性激酶（CDK），它们具有与细胞周期蛋白结合的基序PSTAIRE（CDK-a）和PPTA/TLRE（CDK-b）。烟草（Nicotiana tabacum L. cv Bright Yellow-2）细胞是最易于同步化的植物培养物，但在该系统中尚未有关于CDK活性的详细分析报道。在此，我们描述了从亮黄-2细胞中分离出新的PPTALRE CDKs（Nicta;CdkB1），并对CdkB1以及PSTAIRE CDKA在生长和细胞周期中的mRNA、蛋白质和激酶活性水平进行了详细分析。CdkA和CdkB1转录本在指数生长期细胞中比在静止期细胞中更为丰富，但这两个基因在细胞周期中表现出显著不同的调控方式。在重新进入细胞周期的细胞中，CdkA mRNA和蛋白质在G1期积累，免疫沉淀的组蛋白H1激酶活性在G1/S边界处增加。尽管CdkA mRNA和蛋白质水平没有明显的调控，但阿非迪霉素同步化的细胞在S-G2期显示出最高的CDKA相关组蛋白H1激酶活性。相比之下，CdkB1转录本直到S期都处于非常低的水平，并且在G1期几乎检测不到CDKB1蛋白质和激酶活性。CdkB1 mRNA在S期至M期积累，其相关的激酶活性在G2/M边界处达到峰值，证实了PPTALRE CDKs的转录受细胞周期调控。我们认为CDKA激酶活性可能在G1/S期边界、S期以及G2/M期转变过程中发挥作用，而CDKB1激酶活性仅在G2/M期存在。
