Project description:Eukaryotic chromatin structure is highly conserved, with the canonical histone proteins revealing only small sequence changes across species. Yet, all vertebrates exhibit three much larger histone H2A variants, macroH2A. A distinctive feature of these atypical histones is the globular macrodomain module, which can bind metabolites and is connected to the histone fold through a flexible linker. MacroH2A variants impact heterochromatin organization, transcription regulation and establish a barrier for cellular reprogramming. However, the mechanisms of how these large H2A variants are incorporated into chromatin and the identity of any chaperones required for histone deposition have remained elusive. Here, we developed a split-GFP-based cellular readout for histone incorporation and conducted a genome-wide mutagenesis screen in haploid human cells to identify proteins that regulate macroH2A dynamics. We identified and validated the histone chaperone ANP32B as a regulator of macroH2A chromatin deposition. ANP32B associates with macroH2A in cells and in vitro binds to histones with low nanomolar affinity. In vitro nucleosome assembly assays show that ANP32B stimulates deposition of macroH2A-H2B and not of H2A-H2B onto tetraso me. In cells, depletion of ANP32B in cells strongly affects global macroH2A deposition, revealing ANP32B as a macroH2A chaperone. Our study highlights the power of haploid cell functional genomics coupled with cellular imaging to identify factors that are required for chromatin plasticity and diversity.
Project description:To search for factors regulating neuronal differentiation, we performed a genome-wide loss-of-function CRISPR/Cas9 screen in haploid human ESCs. The regulators were identified by the quantification of depletion of their mutant clones within a pooled loss-of-function library upon neuronal differentiation.
Project description:To search for host factors regulating Zika virus infection, we performed a genome-wide loss-of-function CRISPR/Cas9 screen in haploid human ESCs. The regulators were identified by the quantification of enrichment of their mutant clones within a pooled loss-of-function library upon Zika virus infection.
Project description:To search for host factors regulating SARS-COV-2 infection, we performed a genome-wide loss-of-function CRISPR/Cas9 screen in haploid human ESCs. The regulators were identified by the quantification of enrichment of their mutant clones within a pooled loss-of-function library upon SARS-COV-2 infection.
Project description:To search for factors regulating paternally imprinted genes (PEGs), we performed a genome-wide CRISPR/Cas9 screen in haploid hpESCs, and further analyzed the molecular phenotype upon perturbation of candidate PEGs regulators.
Project description:To search for factors regulating paternally imprinted genes (PEGs), we performed a genome-wide CRISPR/Cas9 screen in haploid hpESCs, and further analyzed the molecular phenotype upon perturbation of candidate PEGs regulators.
Project description:Transcription factor-induced reprogramming of somatic cells to pluripotency is a very inefficient process, probably due to the existence of important epigenetic barriers that are imposed during differentiation and that contribute to preserve cell identity. In an effort to decipher the molecular nature of these barriers, we followed a genome-wide approach, in which we identified macro histone variants (macroH2A) as highly expressed in human somatic cells but downregulated after reprogramming to pluripotency, as well as strongly induced during differentiation. Knock down of macro histone variants in human keratinocytes increased the efficiency of reprogramming to pluripotency, while overexpression had opposite effects. Genome-wide occupancy profiles show that in human keratinocytes macroH2A.1 preferentially occupies genes that are expressed at low levels and are marked with H3K27me3, including pluripotency-related genes and bivalent developmental regulators, at which its presence prevents the regain of H3K4me2 during reprogramming, over imposing an additional layer of repression that preserves cell identity. Gemone wide occupancy of HA:macroH2A.1 in human keratinocytes
Project description:MacroH2As core histone variants have a unique structure that includes C-terminal nonhistone domain. MacroH2As are highly conserved in vertebrates, and are thought to regulate gene expression. However the nature of genes regulated by macroH2As and the biological significance of macroH2As for the organism remain unclear. Our gene expression studies indicate that macroH2A.1 and macroH2A.2 work together to regulate specific genes. In these studies we examine the distributions of macroH2A.1 and macroH2A.2 nucleosomes to determine if they are localized to the genes that show altered expression in macroH2A knockout mouse liver. MacroH2A.1 and macroH2A.2 nucleosomes prepared from ~ 50 fetal mouse livers were purified by thio-affinity chromatography. Five samples were sequenced: Thiopropyl Sepharose, Normal Liver - contains mononucleosomal DNA from macroH2A.1-containing nucleosomes; Activate Thiol Sepharose, Normal Liver - contains mononucleosomal DNA primarily from macroH2A.2-containing nucleosomes. Starting Material, Normal Liver - this is a reference samplefor the first two samples. It contains mononucleosomal DNA from bulk fetal liver chromatin. Activated Thiol Sepharose, Knockout Livers - this is a control sample that contains mononucleosomal DNA from non-macroH2A nucleosomes that contaminate the macroH2A.2 nucleosomes. This fraction was prepared from macroH2A1/2 double knockout fetal livers; Starting Material, Knockout Liver - this is a reference sample for the fourth sample. It contains mononucleosomal DNA from bulk chromatin prepared from macroH2A1/2 double knockout fetal livers.