期刊
BLOOD CELLS MOLECULES AND DISEASES
卷 44, 期 1, 页码 7-15出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bcmd.2009.10.002
关键词
cJun; CREB1; gamma-globin; cAMP response element; ATF-2
类别
资金
- National Heart Lung and Blood Institute [HL69234]
The upstream G gamma-globin gene cAMP response element (G-CRE) was previously shown to play a role in drug-mediated fetal hemoglobin induction. This effect is achieved via p38 mitogen activated protein kinase (MAPK)-dependent CREB1 and ATF-2 phosphorylation and G-CRE transactivation. Since this motif is also a predicted consensus binding site for cJun we extended our analysis to determine the ability of cJun to transactivate gamma-globin through the G-CRE. Using chromatin immunoprecipitation assays we showed comparable in vivo cJun and CREB1 binding to the G-CRE region. Protein-protein interactions were confirmed between cJun/ATF-2 and CREB1/ATF-2 but not between CREB1 and cJun. However, we observed cJun and CREB1 binding to the G-CRE in vitro by electrophoretic mobility shift assay. Promoter pull-down assay followed by sequential western blot analysis confirmed co-localization of cJun, CREB1, and ATF-2 on the G-CRE. To show functional relevance, enforced expression studies with pLen-cJun and a G gamma-promoter (-1500 to +36) luciferase reporter were completed; we observed a concentration-dependent increase in luciferase activity with pLen-cJun similar to that produced by CREB1 enforced expression. Moreover, the G/A mutation at -1225 in the G-CRE abolished cJun transactivation. Finally, enforced cJun expression in K562 cells and normal primary erythroid progenitors enhanced endogenous gamma-globin gene expression. We conclude that these data indicate that cJun activates the G gamma-globin promoter via the G-CRE in a manner comparable with CREB1 and propose a model for gamma-globin activation based on DNA-protein interactions in the G-CRE. (C) 2009 Elsevier Inc. All rights reserved.
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