Might affect PCNA interaction with some CDK (cell division protein kinase) complexes; stimulates DNA excision repair in vitro and inhibits entry of cells into S phase. In T-cells, functions as a regulator of p38 MAPKs by inhibiting p88 phosphorylation and activity. Interacts with AURKA, GADD45GIP1 and PCNA (By similarity). Interacts with MAPK14. By various types of DNA damage and growth arrest. Belongs to the GADD45 family.