期刊
PHARMACOLOGICAL RESEARCH
卷 91, 期 -, 页码 57-68出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.phrs.2014.11.005
关键词
Raptor; mTOR; Sp1; Mithramycin; Erythroid induction; Fetal hemoglobin
资金
- Fondazione Cariparo (Cassa di Risparmio di Padova e Rovigo) [2011]
- UE FP7 THALAMOSS Project (Thalassemia Modular Stratification System for Personalized Therapy of beta-Thalassemia) [306201]
- Telethon [GGP10124]
- Associazione Veneta per la Lotta alla Talassemia (AVLT) [2013]
- AIRC [IG_13575]
Rapamycin, an inhibitor of mTOR activity, is a potent inducer of erythroid differentiation and fetal hemoglobin production in beta-thalassemic patients. Mithramycin (MTH) was studied to see if this inducer of K562 differentiation also operates through inhibition of mTOR. We can conclude from the study that the mTOR pathway is among the major transcript classes affected by mithramycin-treatment in K562 cells and a sharp decrease of raptor protein production and p70S6 kinase is detectable in mithramycin treated K562 cells. The promoter sequence of the raptor gene contains several Sp1 binding sites which may explain its mechanism of action. We hypothesize that the G + C-selective DNA-binding drug mithramycin is able to interact with these sequences and to inhibit the binding of Sp1 to the raptor promoter due to the following results: (a) MTH strongly inhibits the interactions between Sp1 and Sp1-binding sites of the raptor promoter (studied by electrophoretic mobility shift assays, EMSA); (b) MTH strongly reduces the recruitment of Sp1 transcription factor to the raptor promoter in intact K562 cells (studied by chromatin immunoprecipitation experiments, ChIP); (c) Sp1 decoy oligonucleotides are able to specifically inhibit raptor mRNA accumulation in K562 cells. In conclusion, raptor gene expression is involved in mithramycin-mediated induction of erythroid differentiation of K562 cells and one of its mechanism of action is the inhibition of Sp1 binding to the raptor promoter. (C) 2014 The Authors. Published by Elsevier Ltd.
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