Serine/Threonine-Protein Kinase Chk1 (chek1) Xenopus Laevis Recombinant Protein

Serine/threonine-protein kinase which is required for checkpoint-mediated cell cycle arrest and activation of DNA repair in response to the presence of DNA damage or unreplicated DNA. May also negatively regulate cell cycle progression during unperturbed cell cycles. This regulation is achieved by a number of mechanisms that together help to preserve the integrity of the genome. Recognizes the substrate consensus sequence [R-X-X-S/T]. Phosphorylates wee1 at 'Ser-549' and cdc25c at 'Ser-287', which creates binding sites for 14-3-3 proteins which activate wee1 and inhibit cdc25c. Phosphorylates cdc25a at 'Ser-504' which prevents the interaction of cdc25a with CDK2-cyclin E1, CDC2-cyclin A1 and CDC2-cyclin B1. This inhibitory effect does not require 14-3-3 protein binding. Activation of wee1 and inhibition of CDC25 results in increased inhibitory tyrosine phosphorylation of CDK-cyclin complexes and consequent inhibition of cell cycle progression. May promote DNA repair, regulate chromatin assembly and the transcription of genes that regulate cell-cycle progression. May also play a role in replication fork maintenance.