Chk2 functions as a checkpoint protein kinase in response to DNA damage to maintain genomic stability. The yeast homologs are RAD53 and Cds1. The two major upstream controllers of Chk2 are ATM and ATR which are part of the phosphatidylinositol 3-kinase family. When activated, Chk2 targets p53, Brca1, Cdc25A and Cdc25C to cause cell cycle arrest. Chk2 is also known as serine/threonine-protein kinase CHK2, CHEK2, CDS1, LFS2, RAD53, HuCds1, and PP1425.