Functional Study Of TET2 On The ? Globin Activation

Human hemoglobin is a tetramer consisting of two ? chains and two ? chains,functioning in carrying oxygen to each tissues.The imbalance of this tetramer by gene mutations or such would induce blood disorders,such as ?-thalassemia.Normally,there are two human ?-like globin gene clusters switch-events happening during development,?,? and ? globin gene are expressed at embryonic,fetal and adult stage,encoding HBE,HBG and HBB proteins,respectively.One appropriate drug therapy for ?-thalassemia is to induce ? globin gene expression normally silenced at adult stage to compensate shortage of ? globin.However,mechanism underlying the ? globin gene clusters switch is unclear,and thus limited the exploiting of a complete therapy for ? globin induction.This study aims to explore mechanism of ? globin gene activation through a specific factor TET2,a member of TET(Ten Eleven Translocation)family,known to be responsible for regulating gene transcription in the hematopoietic system,through interaction with transcription factors and histone modifications enzymes.To evaluate the role of TET2 in ? globin activation,? globin expression was induced by Hemin or 5-azacytidine drugs,and TET2 was down-regulated by shRNA in K562 cell line.Nearly 6 folds increases was notices after 72 hours of drug treatment,whereas the expression of TET2 was not affected.TET2 knockdown limited the ? globin increase,and the level of CpG methylation on ? globin gene body was extremely low and unmethylated.On the other hand,TET2 knockdown resulted in a differentiation expression on the expression of key erythroid-specific transcription factors,include GATA1,NF-E4 and KLF1 in K562 cell line,in which the facilitated factors for ? globin,GATA1 and NF-E4 decreased to 80%,while the inhibitor KLF1 increased to 1.4 folds of the control.In conclusion,TET2 appears to facilitate ? globin gene expression,and the targets of TET2 are more likely transcription factors than ? globin itself.