Expression of p21WAF1/Cip1 through Sp1 sites by histone deacetylase inhibitor apicidin requires PI 3-kinase-PKCepsilon signaling pathway

Abstract

We previously reported that the activation of p21WAF1/Cip1 transcription by histone deacetylase inhibitor apicidin was mediated through Sp1 sites and pointed to the possible participation of protein kinase C (PKC). In this study, we investigated the role and identity of the specific isoforms of PKC involved and identified phosphatidylinositol 3-kinase (PI 3-kinase) as an upstream effector in HeLa cells. Using an isoform-specific pharmacological inhibitor of PKC, a PKCε dominant-negative mutant, and antisense oligonucleotide to inhibit PKCε specifically, we found that among PKC isoforms, PKCε was required for the p21WAF1/Cip1 expression by apicidin. In addition to PKCε, PI 3-kinase appeared to participate in the activation of p21WAF1/Cip1 promoter by apicidin, since inactivation of PI 3-kinase either by transient expression of dominantnegative mutant of PI 3-kinase or its specific inhibitors, LY294002 and wortmannin, attenuated the activation of p21WAF1/Cip1 promoter and p21WAF1/Cip1 protein expression by apicidin. Furthermore, membrane translocation of PKCε in response to apicidin was blocked by the PI 3-kinase inhibitor, indicating the role of PI 3-kinase as an upstream molecule of PKCε in the p21WAF1/Cip1 promoter activation by apicidin. However, the p21 WAF1/Cip1 expression by apicidin appeared to be independent of the histone hyperacetylation, since apicidin-induced histone hyperacetylation of p21WAF1/Cip1promoter region was not affected by inhibition of PI 3-kinase and PKC, suggesting that the chromatin remodeling through the histone hyperacetylation alone might not be sufficient for the expression of p21 WAF1/Cip1 by apicidin. Taken together, these results suggest that the PI 3-kinase-PKCε signaling pathway plays a pivotal role in the expression of the p21WAF1/Cip1 by apicidin.