The phosphorylation of p65 subunit has been shown to be important for RELA transcriptional activity. Once phosphorylated RELA/p65 has been shown to recruit transcriptional coactivators CREB binding protein (CBP) and p300 (Chen at al. 2002). The association between CBP/p300 and NF-kB p65 occurs through RHD (Rel homology domain) and C-terminal transactivation domain (Zong et al. 1998). Both p300 and CBP contain a histone acetyltransferase (HAT) enzymatic activity that regulates gene expression through acetylation of RELA, and promoter proximal nucleosomal histones, resulting in increased accessibility of the DNA for other essential regulators (Kalkhoven 2004).