Regulation of p300 recruitment on EGF‐induced keratin 16 gene expression in keratinocytes

Abstract

Overexpression of keratin 16 has been observed in keratinocytes in those skin diseases characterized by hyperproliferation such as psoriasis. In studies of gene regulation of keratin 16, we reported previously that the coactivators p300/CBP interacted with Sp1 and AP1 proteins, and participated in EGF-induced keratin16 gene expression in HaCaT cells. According to the documents previously reported, activated ERK2 phosphorylated GST-p300 (aa 1572–2370) in vitro and the transcriptional activity of p300 was enhanced. However, it is still unclear that which kinases are responsible for p300 phosphorylation in vivo and where the exact phosphorylation sites occur upon stimulation. In this study, we clarify the ERK mediated phosphorylation sites of p300 in in vitro kinase assay. According to our preliminary results, EG F treatment was found to up-regulate p300 recruitment to the keratin 16 promoter through ERK signaling pathway. The p300 recruitment was dependent on c-Fos in EGF-treated cells. In addition, the purified N- or C-terminus of p300 protein was phosphorylated by activated ERK2 and phosphorylation of p300 was increased upon EGF treatment in a time-dependent manner in HaCaT cells. These results indicated that ERK-induced phosphorylation of p300 was required for EGF-induced gene expression of K16.