Project description:Human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus that causes an aggressive T-cell malignancy and a variety of inflammatory conditions. The integrated provirus includes a single binding site for the epigenomic insulator, CCCTC-binding protein (CTCF), but its function remains unclear. In the current study, a mutant virus was examined that eliminates the CTCF-binding site. The mutation did not disrupt the kinetics and levels of virus gene expression, or establishment of or reactivation from latency. However, the mutation disrupted the epigenetic barrier function, resulting in enhanced DNA CpG methylation downstream of the CTCF binding site on both strands of the integrated provirus and H3K4Me3, H3K36Me3, and H3K27Me3 chromatin modifications both up- and downstream of the site. A majority of clonal cell lines infected with wild type HTLV-1 exhibited increased plus strand gene expression with CTCF knockdown, while expression in mutant HTLV-1 clonal lines was unaffected. These findings indicate that CTCF binding regulates HTLV-1 gene expression, DNA and histone methylation in an integration site dependent fashion.
Project description:We compared histone modifications of wild type and HTLV-1ΔCTCF provirus by ChIP sequencing and observed that loss of the vrial CTCF binding site in HTLV-1 results in increased histone methylation 5’ and 3’ of the CTCF site, suggesting that CTCF binding may act as a boundary element to epigenetic modification.
Project description:Efficient treatment of Acute Myeloid Leukemia (AML) patients remains a challenge despite recent advances. Here using a CRISPRi screen targeting chromatin factors, we identified BPTF as an essential regulator of AML cell survival. We demonstrate that BPTF forms an alternative NURF chromatin remodeling complex with SMARCA5 and BAP18, which regulates the accessibility of a large set of insulator regions in leukemic cells. This ensures efficient CTCF binding and boundary formation between topologically associated domains that is essential for maintaining the leukemic transcriptional programs. We also demonstrate that the well-studied PHD2-BROMO chromatin reader modules of BPTF, while contributing to complex recruitment to chromatin, are dispensable for leukemic cell growth. Taken together, our results uncover how the alternative NURF complex contributes to leukemia and provide a rationale for its targeting in AML.
Project description:CTCF and Cp190 proteins are implicated at many insulator elements throughout Drosophila genome. Here we compared Hi-C maps, transcriptomes and binding of multiple insulator proteins in cultured Drosophila cells derived from CTCF-KO, Cp190-KO and control embryos.
Project description:Chromatin insulators and Polycomb group (PcG) complexes control nuclear organization to effect changes in gene expression. In Drosophila, RNA silencing pathways influence long range interactions mediated by PcG proteins and nuclear localization of the gypsy insulator; however, the underlying mechanisms are unknown. Here, we identify a singular requirement for Argonaute2 (AGO2) for the activity of the CCCTC-binding factor (CTCF)/Centrosomal protein 190 (CP190) dependent Fab-8 insulator. AGO2 and CP190 interact physically, and genome wide localization of AGO2 by chromatin immunoprecipitation and sequencing (ChIP-seq) reveals extensive colocalization of AGO2 with insulators and Polycomb Response Elements (PREs) but minimal overlap with regions of endogenous small interfering RNA (endo-siRNA) production. Finally, depletion of either CTCF or CP190 results in loss of AGO2 association with insulators, PREs, and other cis-regulatory regions. Our findings suggest that Dicer-independent recruitment of AGO2 to chromatin by insulator proteins promotes the definition of transcriptional domains throughout the genome. ChIP-seq of AGO2 in two Drosophila cell types (S2 and S3)
Project description:CTCF and Cp190 proteins are implicated at many insulator elements throughout Drosophila genome. Here we compared Hi-C maps, transcriptomes and binding of multiple insulator proteins in cultured Drosophila cells derived from CTCF-KO, Cp190-KO and control embryos.
Project description:CTCF and Cp190 proteins are implicated at many insulator elements throughout Drosophila genome. Here we compared Hi-C maps, transcriptomes and binding of multiple insulator proteins in cultured Drosophila cells derived from CTCF-KO, Cp190-KO and control embryos.
Project description:Catalytic activity of the ISWI family of remodelers is critical for nucleosomal organization and transcription factor binding, including the insulator protein CTCF. To define which subcomplex mediates these diverse functions we phenotyped a panel of isogenic mouse stem cell lines each lacking one of six ISWI accessory subunits. Individual deletions of either CERF, RSF1, ACF, WICH or NoRC subcomplexes only moderately affect the chromatin landscape, while removal of the NURF-specific subunit BPTF leads to drastic reduction in chromatin accessibility and Snf2h ATPase localization around CTCF sites. While this reduces distances to the adjacent nucleosomes it only modestly impacts CTCF binding itself. In absence of accessibility, the insulator function of CTCF is nevertheless impaired resulting in lower occupancy of cohesin and cohesin-loading factors, and reduced insulation at these sites, highlighting the need of NURF-mediated remodeling for open chromatin and proper CTCF function. Our comprehensive analysis reveals a specific role for NURF in mediating Snf2h localization and chromatin opening at bound CTCF sites showing that local accessibility is critical for cohesin binding and insulator function.
Project description:CCCTC binding factor (CTCF) has been implicated in mediating chromatin insulation and long-distance interactions between enhancer and promoter. In this study, to study the roles of CTCF in somatic cell reprogramming, we performed RNA-seq, Hi-C, ChIP-seq and ATAC-seq at the specific stage of reprogramming. Through bioinformatics analysis, our data indicated that CTCF promotes enhancer-promoter interactions and chromatin accessibility to regulate the expression of key pluripotency genes; meanwhile, it serves as an insulator to suppress the expression of key somatic genes. Smarca5 loss inhibits CTCF-promoted reprogramming by reversing CTCF insulator activity on MEF-specific genes and leading to incorrect nucleosome positioning adjacent to CTCF binding sites. These findings reveal the dual functions of CTCF as both a structural regulator and insulator in conjunction with a key chromatin remodeler to drive cellular reprogramming towards pluripotency.
Project description:CCCTC binding factor (CTCF) has been implicated in mediating chromatin insulation and long-distance interactions between enhancer and promoter. In this study, to study the roles of CTCF in somatic cell reprogramming, we performed RNA-seq, Hi-C, ChIP-seq and ATAC-seq at the specific stage of reprogramming. Through bioinformatics analysis, our data indicated that CTCF promotes enhancer-promoter interactions and chromatin accessibility to regulate the expression of key pluripotency genes; meanwhile, it serves as an insulator to suppress the expression of key somatic genes. Smarca5 loss inhibits CTCF-promoted reprogramming by reversing CTCF insulator activity on MEF-specific genes and leading to incorrect nucleosome positioning adjacent to CTCF binding sites. These findings reveal the dual functions of CTCF as both a structural regulator and insulator in conjunction with a key chromatin remodeler to drive cellular reprogramming towards pluripotency.