Abstract:

Reactivation of fetal hemoglobin expression by the downregulation of BCL11A is a promising treatment for β-hemoglobinopathies. A detailed understanding of BCL11A-mediated repression of γ-globin gene (HBG1/2) transcription is lacking, as studies to date used perturbations by shRNA or CRISPR-Cas9 gene editing. We leveraged the dTAG PROTAC degradation platform to acutely deplete BCL11A protein in erythroid cells and examined consequences by nascent transcriptomics, proteomics, chromatin accessibility, and histone profiling. Among 31 genes repressed by BCL11A, HBG1/2 and HBZ show the most abundant and progressive changes in transcription and chromatin accessibility upon BCL11A loss. Transcriptional changes at HBG1/2 were detected in <2 h. Robust HBG1/2 reactivation upon acute BCL11A depletion occurred without the loss of promoter 5-methylcytosine (5mC). Using targeted protein degradation, we establish a hierarchy of gene reactivation at BCL11A targets, in which nascent transcription is followed by increased chromatin accessibility, and both are uncoupled from promoter DNA methylation at the HBG1/2 loci. [Display omitted] •PROTAC-mediated degradation of BCL11A reactivates high-level γ-globin expression•BCL11A represses <31 primary target genes; HBG, HBZ most induced upon BCL11A loss•Presence of BCL11A is the major barrier to γ-globin promoter activation•Upon BCL11A loss, increased chromatin accessibility closely follows transcription Reactivation of γ-globin by the downregulation of BCL11A expression is a promising strategy for the treatment of sickle cell disease. In this issue of Cell Chemical Biology, Mehta et al. use PROTAC-mediated depletion of BCL11A to identify a small set of target genes and chart the kinetics of γ-globin induction.