Diverse phosphoregulatory mechanisms controlling cyclin-dependent kinase-activating kinases in Arabidopsis

• Published in: The Plant journal : for cell and molecular biology 2006-09, Vol.47 (5), p.701-710x
• Main Authors: Shimotohno, Akie, Ohno, Ryoko, Bisova, Katerina, Sakaguchi, Norihiro, Huang, Jirong, Koncz, Csaba, Uchimiya, Hirofumi, Umeda, Masaaki
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Arabidopsis - anatomy & histology; Arabidopsis - enzymology; Arabidopsis - growth & development; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis Proteins - physiology; Biological and medical sciences; Botany; CDK‐activating kinase; Cell cycle; Cell kinetics; Cell physiology; Cyclin H; Cyclin-Dependent Kinases - genetics; Cyclin-Dependent Kinases - metabolism; Cyclin-Dependent Kinases - physiology; Cyclins - metabolism; cyclin‐dependent kinase; Down-Regulation; Enzymes; Flowers & plants; Fundamental and applied biological sciences. Psychology; Genotype & phenotype; Models, Biological; Molecular Sequence Data; Phosphorylation; Plant physiology and development; Plant Roots - cytology; Plant Roots - enzymology; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; Protein-Serine-Threonine Kinases - physiology; Proteins; Protoplasts - cytology; Protoplasts - enzymology; Sequence Alignment; transcription; Tyrosine - metabolism; WEE1
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2006.02820.x

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.