The histone acetylation mediated by Gcn5 regulates the Hoxc11 gene expression in MEFs

Hox genes are responsible for encoding transcription factors that are essential for anterior-posterior body patterning at early stages of embryogenesis. However, detailed mechanisms of Hox genes are yet to be defined. Protein kinase B alpha (Akt1) was previously identified as a possible upstream regulator of Hox genes. Furthermore, the Hoxc11 gene has been upregulated in Akt1 null (Akt1-/-) mouse embryonic fibroblasts (MEFs), while repressed in wild-type MEFs. In this study, we propose to investigate the role of Gcn5, a histone acetyltransferase, in the regulation of Hoxc11 expression in MEFs. We showed that the H3 lysine 9 acetylation (H3K9ac) status has the same correlation with Hoxc11 expression and reported that Gcn5 is associated with the upregulation of Hoxc11 expression through H3K9ac in Akt1-/- MEFs. Since Hoxc11 was upregulated through histone acetylation in Akt1-/- MEFs, a functional role of Gcn5 on Hoxc11 expression was analyzed in Akt1-/- MEFs treated with Gcn5 specific inhibitor or transfected with Gcn5-small interfering RNA (Gcn5-siRNA). When the expression of Hoxc11 was analyzed using RT-PCR and real-time PCR, the Hoxc11 mRNA level was found to be similar in both Akt1-/- MEFs and control-siRNA transfected Akt1-/- MEFs. However, the Hoxc11 expression level was decreased in Gcn5-inhibited or Gcn5-knockdown Akt1-/- MEFs. Additionally, to analyze Gcn5-mediated histone acetylation status, chromatin immunoprecipitation assay was carried out in Gcn5-siRNA-transfected Akt1-/- MEFs. The H3K9ac at the Hoxc11 locus was decreased in Gcn5-knockdown Akt1-/- MEFs compared to controls. Based on these findings, we conclude that Gcn5 regulates Hoxc11 gene expression through mediating site-specific H3K9 acetylation in Akt1-/- MEFs.