Reactive oxygen species (ROS) are a continuous hazard in eukaroytic cells by their ability to cause damage to biomolecules, in particular to DNA. Previous data indicated that the cytosolic serine peptidase tripeptidyl-peptidase II (TPPII) translocates into the nucleus of most tumor cell lines in response to gamma-irradiation and ROS production; an event that promoted p53 expression as well as caspase-activation. We here observed that nuclear translocation of TPPII was dependent on signaling by MAP kinases, including p38MAPK. Further, this was caused by several types of DNA-damaging drugs, a DNA cross-linker (cisplatinum), an inhibitor of topoisomerase II (etoposide), and to some extent also by nucleoside-analogues (5-fluorouracil, hydroxyurea). In the minority of tumor cell lines where TPPII was not translocated into the nucleus in response to DNA damage we observed reduced intracellular ROS levels, and the expression levels of redox defense systems were increased. Further, treatment with the ROS-inducer gamma-hexa-chlorocyclohexane (gamma-HCH, lindane), an inhibitor of GAP junctions, restored nuclear translocation of TPPII in these cell lines upon gamma-irradiation. Moreover, blocking nuclear translocation of TPPII in etoposide-treated cells, by using a peptide-derived inhibitor (Z-Gly-Leu-Ala-OH), attenuated expression of gamma-H2AX in gamma-irradiated melanoma cells. Our results indicated a role for TPPII in MAPK-dependent DNA damage signaling. (C) 2010 Elsevier Inc. All rights reserved.