Cryo-EM structure of the CDK2-cyclin A-CDC25A Complex

The cell division cycle 25 phosphatases CDC25A, B and C regulate cell cycle transitions by dephosphorylating residues in the conserved glycine-rich motif of cyclin-dependent protein kinases (CDKs) to activate CDK activity. Here, we present the cryogenic-electron microscopy (cryo-EM) structure of CDK2-cyclin A in complex with CDC25A at 2.91 Å resolution, providing a detailed structural analysis of the overall complex architecture and key protein-protein interactions that underpin this 86 kDa complex. We further reveal an unanticipated CDC25A C-terminal helix that is critical for complex formation. Sequence conservation analysis suggests CDK1/2-cyclin A, CDK1-cyclin B and CDK2/3-cyclin E are suitable binding partners for CDC25A, whilst CDK4/6-cyclin D complexes appear unlikely substrates. A comparative structural analysis of CDK-containing complexes also confirms the functional importance of the conserved CDK1/2 GDSEID motif. This structure improves our understanding of the roles of CDC25 phosphatases in CDK regulation and may inform the development of CDC25- targeting anticancer strategies. ### Competing Interest Statement The other authors declare no competing interests. The authors declare no competing financial interest. Some work in the authors laboratory is supported by a research grant from Astex Pharmaceuticals. SK is currently an employee of FujiFilm, Billingham, UK; MS is currently and employee of Evotec, Milton, UK. * CDK : cyclin-dependent kinase CBF : cyclin-box fold SEC : size exclusion chromatography HDX : Hydrogen-Deuterium Exchange HTRF : Homogenous Time-Resolved Florescence FSC : Fourier shell correlation CTF : contrast transfer function.