Dynamic histone acetylation, catalyzed by lysine acetyltransferases and HDACs, is critical to IEG expression. Expression of IEGs, such as FOSL1, is induced by several signal transduction pathways resulting in activation of the protein kinase MSK and phosphorylation of histone H3 at serine 10 of nucleosomes (the nucleosome response) at the upstream promoter and regulatory region of target genes. HDAC inhibitors prevent FOSL1 gene induction and the association of HDAC1, 2 and 3 with the gene body. However, HDAC inhibitors did not prevent the nucleosome response. Thus HDAC inhibitors perturb events downstream of the nucleosome response required for FOSL1 transcription initiation.