Earlier, we reported that the transcriptional repressor promyelocytic leukemia zinc-finger protein (PLZF) is sumoylated at position K242, and the sumoylation regulated its biological function. Here, we show that the sumoylation site can be modified by ubiquitin. The stability and nuclear localization of PLZF were regulated by the antagonistic relationship between sumoylation and ubiquitination. We observed the antagonistic effects of ubiquitin and SUMO-1 on PLZF under oxidative stress induced by serum deprivation. Thus, the choice between modification of PLZF by SUMO or ubiquitin was determined by the intracellular level of ROS, which was generated by serum deprivation that inactivated the SUMO-conjugating enzymes Uba2 and Ubc9, and resulted in decrease of sumoylation. The ubiquitination was increased under these conditions. The expression of BID, a known transcriptional target protein of PLZF, was decreased, and the consequent apoptosis was induced by the ROS generated during serum starvation. On the basis of these results, we propose that PLZF post-translational modification is controlled by intracellular ROS, and the biological function of PLZF is regulated by sumoylation and ubiquitination. (C) 2008 Elsevier Inc. All rights reserved.