Maize CDKA2;1a and CDKB1;1 kinases have different requirements for their activation and participate in substrate recognition

• Published in: The FEBS journal 2023-05, Vol.290 (9), p.2463-2488
• Main Authors: López‐Hernández, Mingyar N., Vázquez‐Ramos, Jorge M.
• Format: Article
• Language: English
• Subjects: activation mechanism; Animals; autophosphorylation; Cell cycle; Corn; Cyclin-dependent kinase; Cyclin-Dependent Kinases - metabolism; Cyclins - genetics; Cyclins - metabolism; E coli; Escherichia coli - metabolism; Kinases; maize CDKs; Phosphorylation; Protein Serine-Threonine Kinases - metabolism; Proteins; Recognition; Saccharomyces cerevisiae - metabolism; Scaffolding; substrate recognition; Substrate specificity; Substrates; Threonine; Yeasts; Zea mays - genetics
• ISSN: 1742-464X; 1742-4658
• DOI: 10.1111/febs.16659

Cyclin‐dependent kinases (CDKs), in association with cyclins, control cell cycle progression by phosphorylating a large number of substrates. In animals, activation of CDKs regularly requires both the association with a cyclin and then phosphorylation of a highly conserved threonine residue in the CDK activation loop (the classical mechanism), mediated by a CDK‐activating kinase (CAK). In addition to this typical mechanism of activation, some CDKs can also be activated by the association of a cyclin to a monomeric CDK previously phosphorylated by CAK although not all CDKs can be activated by this mechanism. In animals and yeast, cyclin, in addition to being required for CDK activation, provides substrate specificity to the cyclin/CDK complex; however, in plants both the mechanisms of CDKs activation and the relevance of the CDK‐associated cyclin for substrate targeting have been poorly studied. In this work, by co‐expressing proteins in E. coli, we studied maize CDKA2;1a and CDKB1;1, two of the main types of CDKs that control the cell cycle in plants. These kinases could be activated by the classical mechanism and by the association of CycD2;2a to a phosphorylated intermediate in its activation loop, a previously unproven mechanism for the activation of plant CDKs. Unlike CDKA2;1a, CDKB1;1 did not require CAK for its activation, since it autophosphorylated in its activation loop. Phosphorylation of CDKB1;1 and association of CycD2;2 was not enough for its full activation as association of maize CKS, a scaffolding protein, differentially stimulated substrate phosphorylation. Our results suggest that both CDKs participate in substrate recognition. The mechanism regulating CDK activity in yeast and mammals has been thoroughly studied; however, the corresponding to plant CDKs is largely unknown. Here, we report that maize CDKA2;1a requires CAK phosphorylation for full activation whereas CDKB1;1 autophosphorylates, but also requires an additional factor (CKS) for full activation. Both monomeric CDKs can be CAK phosphorylated and activated by CycD2;2a association, and both CDKs participate in substrate recognition.