Developmental silencing of human zeta-globin gene expression is mediated by the transcriptional repressor RREB1.
The mammalian embryonic zeta-globin genes, including that of humans, are expressed at the early embryonic stage and then switched off during erythroid development. This autonomous silencing of the zeta-globin gene transcription is probably regulated by the cooperative work of various protein-DNA and protein-protein complexes formed at the zeta-globin promoter and its upstream enhancer (HS-40). We present data here indicating that a protein-binding motif, ZF2, contributes to the repression of the HS-40-regulated human zeta-promoter activity in erythroid cell lines and in transgenic mice. Combined site-directed mutagenesis and EMSA suggest that repression of the human zeta-globin promoter is mediated through binding of the zinc finger factor RREB1 to ZF2. This model is further supported by the observation that human zeta-globin gene transcription is elevated in the human erythroid K562 cell line or the primary erythroid culture upon RNA interference (RNAi)(2) knockdown of RREB1 expression. These data together suggest that RREB1 is a putative repressor for the silencing of the mammalian zeta-globin genes during erythroid development. Because zeta-globin is a powerful inhibitor of HbS polymerization, our experiments have provided a foundation for therapeutic up-regulation of zeta-globin gene expression in patients with severe hemoglobinopathies.
Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan.
Ruei-Lin
RL
Chen
Yu-Chi
YC
Chou
Yii-Jenq
YJ
Lan
Ting-Shuo
TS
Huang
C-K James
CK
Shen
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015153:Blotting, Western; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D006801:Humans; D020014:K562 Cells; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D055543:zeta-Globins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C101743:RREB1 protein, human; D012097:Repressor Proteins; D014157:Transcription Factors; D055543:zeta-Globins