Gcn5 Modulates the Cellular Response to Oxidative Stress and Histone Deacetylase Inhibition

To identify chemical genetic interactions underlying the mechanism of action of histone deacetylase inhibitors (HDACi) a yeast deletion library was screened for hypersensitive deletion mutants that confer increased sensitivity to the HDACi, CG-1521. The screen demonstrated that loss of GCN5 or deletion of components of the Gcn5 histone acetyltransferase (HAT) complex, SAGA, sensitizes yeast to CG-1521-induced cell death. Expression profiling after CG-1521 treatment reveals increased expression of genes involved in metabolism and oxidative stress response, and oxidative stress response mutants are hypersensitive to CG-1521 treatment. Accumulation of reactive oxygen species and increased cell death are enhanced in the gcn5Δ deletion mutant, and are abrogated by anti-oxidants, indicating a central role of oxidative stress in CG-1521-induced cell death. In human cell lines, siRNA mediated knockdown of GCN5 or PCAF, or chemical inhibition of GCN5 enzymatic activity, increases the sensitivity to CG-1521 and SAHA. These data suggest that the combination of HDAC and GCN5/PCAF inhibitors can be used for cancer treatment.