The tumor suppressor protein p53 is intimately involved in the cellular response to DNA damage, controlling cell cycle arrest, apoptosis and the transcriptional induction of DNA damage inducible genes. A transcriptional target of p53, Gadd45, was recently found to bind to PCNA, a component of DNA replication/repair complexes, thereby implicating Gadd45 in DNA metabolism. Using biochemical assays, a role for Gadd45 in excision repair in vitro has been demonstrated. Antisense experiments have also indicated an in vivo role for the GADD45 gene in UV-irradiation survival. These discoveries establish a link between p53 and DNA repair through Gadd45.