p38 MAP kinase activation mediates gamma-globin gene induction in erythroid progenitors.
OBJECTIVE
Our goal was to determine the role of p38 mitogen-activated protein kinase (MAPK) signaling in fetal hemoglobin (HbF) induction. Two histone deacetylase inhibitors (HDAIs), sodium butyrate (NB), and trichostatin (TSA) and hemin were analyzed. In addition, the effect of direct activation of p38 MAPK on gamma-globin gene activity was studied.


METHODS
Primary erythroid progenitors derived from peripheral blood mononuclear cell and K562 erythroleukemia cells were analyzed. Cells were grown in NB, TSA, hemin, or anisomycin either alone or in the presence of the p38 MAPK inhibitor SB203580. The effects of the various treatments on gamma-globin RNA, HbF, and phosphorylated p38 MAPK levels were measured by RNase protection assay, alkaline denaturation, and Western blot analysis, respectively. A K562 stable line overexpressing constitutively active p38 MAPK was established using MAPK kinase kinase 3 (MKK3) and MKK6, the immediate upstream activators of p38. The direct effect of p38 MAPK overexpression on gamma-globin mRNA synthesis was analyzed.


RESULTS
NB and TSA activated p38 MAPK and increased gamma-globin mRNA levels in K562 cells and primary erythroid progenitors. Pretreatment with SB203580 blocked p38 MAPK and gamma-globin gene activation. In contrast, no change in p38 activity was observed with hemin inductions. Direct activation of p38 by anisomycin or constitutive overexpression also increased gamma-globin mRNA in the absence of HbF inducers in wild-type K562 cells and in the MKK stable lines.


CONCLUSIONS
This study supports a novel role for p38 MAPK in gamma-globin regulation in human erythroid progenitors.
Department of Molecular and Cell Biology, University of Texas at Dallas, Richardson, Tex. 75083, USA. bpace@utdallas.edu
Betty S
BS
Pace
Xin-hua
XH
Qian
Jose
J
Sangerman
Solomon F
SF
Ofori-Acquah
B Surendra
BS
Baliga
Jiahuai
J
Han
Stuart D
SD
Critz
D002087:Butyrates / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015672:Erythroid Precursor Cells / Q000378:metabolism*; D005319:Fetal Hemoglobin / Q000235:genetics; D005786:Gene Expression Regulation; D005914:Globins / Q000235:genetics*; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D020014:K562 Cells; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D015533:Transcriptional Activation; D048051:p38 Mitogen-Activated Protein Kinases
D002087:Butyrates; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; C012589:trichostatin A; D005914:Globins; D005319:Fetal Hemoglobin; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases