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Let-7 miRNAs repress HIC2 to regulate BCL11A transcription and hemoglobin switching [Capture-C]

ABSTRACT: The fetal hemoglobin (HBG) regulator BCL11A is repressed by HIC2 to regulate hemoglobin switching. HIC2 itself is under developmental control, highly expressed in fetal tissues and decreased in adult cells, but the mechanism of this developmental regulation is unclear. Here, we demonstrate that HIC2 is developmentally controlled by miRNAs, and loss of global miRNA biogenesis through DICER1 depletion leads to upregulation of HIC2 and HBG. We subsequently identify the adult-expressed let-7 miRNA family as a repressor of HIC2 expression. Ectopic expression of let-7 in fetal-type cells repressed HIC2 levels, while let-7 inhibition in adult erythroblasts upregulated HIC2 levels. Let-7 regulates BCL11A and HBG through induction of HIC2 and reduction of GATA1 binding at the BCL11A erythroid enhancer. Finally, HIC2 depletion rescues BCL11A-mediated repression of fetal hemoglobin in let-7 inhibited cells. Together these data demonstrate a key miRNA-mediated mechanism for developmental regulation of BCL11A expression and fetal hemoglobin repression in adult erythroid cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE216194 | GEO | 2024/02/05

REPOSITORIES: GEO

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Project description:Basak A, Munschauer M, Lareau CA, Montbleau KE, Ulirsch JC, Hartigan CR, Schenone M, Lian J, Wang Y, Huang Y, Wu X, Gehrke L, Rice CM, An X, Christou HA, Mohandas N, Carr SA, Orkin SH, Chen JJ, Lander ES, and Sankaran VG. Increased production of the beta-like gamma-globin genes that form fetal hemoglobin can ameliorate the severity of sickle cell disease and beta-thalassemia, the major hemoglobin disorders. BCL11A is a key repressor of the gamma-globin genes and is expressed in a developmental stage-specific manner to regulate the physiologic fetal-to-adult hemoglobin switch. Despite extensive studies, the upstream mechanisms underlying the developmental expression of BCL11A and hemoglobin switching in humans have remained mysterious. Here we show that BCL11A is regulated at the level of mRNA translation during human hematopoietic development. While BCL11A mRNA is comparably expressed at all developmental stages in erythroid cells, robust protein expression only occurs in adult erythroid cells. Importantly, at the earlier stages of development, the observed reduction in protein expression is attributable to decreased synthesis and not increased degradation of BCL11A. While BCL11A protein is not well synthesized at these earlier stages of development, its mRNA curiously continues to be associated with ribosomes. Through unbiased proteomic analyses in erythroid cells, we demonstrate that the RNA-binding protein LIN28B, which is developmentally expressed in a reciprocal pattern to BCL11A, directly interacts with ribosomes. We show that the observed suppression of BCL11A protein translation is mediated by LIN28B through a direct interaction with BCL11A mRNA and independent of its role in let-7 microRNA biogenesis. Finally, we show that BCL11A is the major functional target in LIN28B-mediated fetal hemoglobin induction. Our results reveal a previously unappreciated regulatory mechanism underlying human hemoglobin switching and illuminate opportunities for developing improved treatments for sickle cell disease and beta-thalassemia.

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Let-7 miRNAs repress HIC2 to regulate BCL11A transcription and hemoglobin switching [Capture-C]

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