Both RASSF2A (Ras-associated family 2A) and p300 are implicated in apoptosis. However, little is known about the interrelationship between these two proteins in induction of apoptosis. Here we show that p300 was able to induce late apoptosis through up-regulation of RASSF2A in human gastric cancer cells SGC-7901 (p53-mutant). Our data demonstrated that p300 stimulated RASSF2A expression in 293T cells in cooperation with the transcription factor Sp1. Results of ChIP (chromatin immunoprecipitation) assays revealed that p300 induced histones H3 and H4 hyperacetylation at RASSF2A promoter. Moreover, p300 and Sp1 reciprocally facilitated their binding to RASSF2A promoter. Overall, data arising from this study indicate that Sp1-mediated RASSF2A gene transcription is activated by p300 through histone acetylation, and this activation plays an important role in inducing late apoptosis.