CHEK1
Encyclopedia
Serine/threonine-protein kinase Chk1 is an enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that in humans is encoded by the CHEK1 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

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Chk1 is a kinase that phosphorylates cdc25, an important phosphatase in cell cycle control, particularly for entry into mitosis. Cdc25, when phosphorylated on serine 216 by chk1 becomes bound by an adaptor protein in the cytoplasm. Therefore it is inhibited from removing the inhibiting phosphate from MPF (mitotic/maturation promoting factor) added by Wee1. Consequently, a cell is prevented from entering mitosis.

Further reading

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