title: Diverse phosphoregulatory mechanisms controlling cyclin-dependent kinase-activating kinases in Arabidopsis.
abstract: 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.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-0032, Japan.
authors.forename: Akie
authors.initials: A
authors.lastname: Shimotohno
authors.forename: Ryoko
authors.initials: R
authors.lastname: Ohno
authors.forename: Katerina
authors.initials: K
authors.lastname: Bisova
authors.forename: Norihiro
authors.initials: N
authors.lastname: Sakaguchi
authors.forename: Jirong
authors.initials: J
authors.lastname: Huang
authors.forename: Csaba
authors.initials: C
authors.lastname: Koncz
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Uchimiya
authors.forename: Masaaki
authors.initials: M
authors.lastname: Umeda
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000033:anatomy & histology / Q000201:enzymology* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D056748:Cyclin H; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D016213:Cyclins / Q000378:metabolism; D015536:Down-Regulation; D008954:Models, Biological; D008969:Molecular Sequence Data; D010766:Phosphorylation; D018517:Plant Roots / Q000166:cytology / Q000201:enzymology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011523:Protoplasts / Q000166:cytology / Q000201:enzymology; D016415:Sequence Alignment; D014443:Tyrosine / Q000378:metabolism; D000095043:Cyclin-Dependent Kinase-Activating Kinase
chemical_list: D029681:Arabidopsis Proteins; D056748:Cyclin H; D016213:Cyclins; D014443:Tyrosine; C112244:Cak1at protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; C514674:WEE1 protein, Arabidopsis; C514673:CDKD;2 protein, Arabidopsis; C000610748:CDKD;3 protein, Arabidopsis; D018844:Cyclin-Dependent Kinases; D000095043:Cyclin-Dependent Kinase-Activating Kinase