Dual-specificity protein phosphatases remove phosphate groups from phosphorylated tyrosine and serine / threonine residues.

All mammals examined to date have three homologues of the ancestral Cdc25 gene (found e.g. in the fungus species S. pombe), designated Cdc25A, Cdc25B, and Cdc25C.

In contrast, some invertebrates harbour two (e.g., the Drosophila proteins String and Twine) or four (e.g., C. elegans Cdc-25.1 - Cdc-25.4) homologues.

CDC25A is specifically degraded in response to DNA damage, resulting in cell cycle arrest.

Thus, this degradation represents one axis of a DNA damage checkpoint, complementing induction of p53 and p21 in the inhibition of CDKs.