Regulation of γ-globin gene expression involves signaling through the p38 MAPK/CREB1 pathway

In response to sodium butyrate and trichostatin A treatment in erythroid cells, p38 mitogen activated protein kinase (MAPK) mediates fetal hemoglobin (HbF) induction by activating cAMP response element binding protein 1 (CREB1). To expand on this observation, we completed studies to determine the role of p38 MAPK in steady-state gamma-globin regulation. We propose that p38 signaling regulates G gamma-globin transcription during erythroid maturation through its downstream effector CREB1 which binds the G gamma-globin cAMP response element (G-CRE). We demonstrated that a loss of p38 or CREB1 function by siRNA knockdown resulted in target gene silencing. Moreover, gain of p38 or CREB1 function augments gamma-globin transcription. These regulatory effects were conserved under physiological conditions tested in primary erythroid cells. When the G-CRE was mutated in a stable chromatin environment G gamma-globin promoter activity was nearly abolished. Furthermore, introduction of mutations in the G-CRE abolished G gamma-globin activation via p38 MAPK/CREB1 signaling. Chromatin immunoprecipitation assays (ChIP) demonstrated that CREB1 and its binding partner CREB binding protein (CBP) co-localize at the G-CRE region. These data support the role of p38 MAPK/CREB1 signaling in G gamma-globin gene transcription under steady-state conditions. (C) 2011 Elsevier Inc. All rights reserved.