Supplementary Components1

Supplementary Components1. precursors. We find essential for fetal hemoglobin (HbF) control a nonredundant subcomplex of NuRD protein family paralogs, whose composition we corroborate by affinity chromatography and proximity labeling mass spectrometry proteomics. Mapping top functional guide RNAs identifies key protein interfaces where in-frame alleles result in loss-of-function due to destabilization or altered function of subunits. We ascertain mutations of that dissociate its requirement for cell fitness from HbF repression in both main human erythroid precursors and transgenic mice. Finally we demonstrate that sequestering CHD4 from NuRD phenocopies these mutations. This work indicates a generalizable approach to discover protein complex features amenable to rational biochemical targeting. Editorial summary: Comprehensive CRISPR mutagenesis targeting all members of the NuRD complex identifies a specific sub-complex required for fetal globin silencing and informs a rational targeting strategy for elevating globin levels while avoiding cytotoxicity. Severe hemoglobinopathies resulting from mutations of the adult -globin gene including sickle cell disease (SCD) and -thalassemia impact millions worldwide1,2. Derepression of the fetal -globin genes (results in de-repression of -globin in -YAC transgenic mice and cultured murine chemical inducer of dimerization (CID) hematopoietic cells17. Knockdown of in main human erythroid cells results in robust increase in -globin expression16,18. A coiled-coil protein conversation between MBD2 and GATAD2A is necessary for -globin gene repression and could be considered a potential focus on for molecular interruption15. Genetic chemical substance or knockdown inhibition of HDAC1 and HDAC2 induces HbF in mature erythroid progenitors19-21. Originally uncovered by GWAS being a locus connected with HbF level22,23, the transcriptional repressor BCL11A has been validated as a critical unfavorable regulator of -globin expression24-32. Biochemical studies have revealed that BCL11A actually interacts with NuRD complex subunits including CHD3/4, HDAC1/2, MTA1/2/3, RBBP4/7, MBD316. More recently has been reported as a TNFRSF13C -globin repressor33. ZBTB7A confers its repressive activity nonredundantly with BCL11A, yet also actually interacts with NuRD subunits including MTA2, HDAC1/2, GATAD2B. Together these data provide the impetus to define the mechanisms through which NuRD represses HbF and to identify possible molecular targets for pharmacotherapy (also observe Supplementary Note). Here we investigated the coding sequences within the NuRD complex associated with HbF repression by using CRISPR-Cas9 dense mutagenesis in human umbilical cord blood-derived erythroid progenitor (HUDEP-2) adult-stage erythroid cells. Taking into account cellular fitness as a counter-screen, we nominated potential NuRD target regions for therapeutic de-repression of HbF that escape cellular PHA-793887 toxicity, validated their effects in primary human cells and transgenic mice, PHA-793887 and developed a rational therapeutic strategy for HbF induction to phenocopy potent mutations. Results CRISPR dense in situ mutagenesis reveals NuRD complex members essential for HbF repression We hypothesized that CRISPR-Cas9 dense in situ mutagenesis could reveal crucial NuRD sequences at which in-frame alleles result in loss-of-function. We compared HbF enrichment scores among the different NuRD subunits (Fig. 1a, also observe Supplementary Note). As expected, sgRNAs targeting positive control genes and showed strong HbF enrichment as compared to nontargeting (NT) sgRNAs (Fig. 1b). We defined hit genes, i.e. those with biological phenotype, as those at which PHA-793887 at least 75% of the sgRNAs exceeded the median NT sgRNA score34. We discovered that among the 13 PHA-793887 NuRD subunit genes, only 5 genes, and was required for HbF repression while was not, was required for HbF repression while and were not, and so forth. This observation suggested that a subcomplex of NuRD defined by constituent paralogous family members was required for -globin repression. Open in a separate windows Fig. 1: Dense mutagenesis of.