Project description:We used homologous recombination based CRISPR Knock-in strategy to insert a SFB tag at C terminal of 53BP1 in 293T cells. We performed tandem affinity purification of endogenous 53BP1 in both soluble and chromatin fraction to uncover known and new 53BP1 binding proteins which might play roles in DNA damage response. We identified and examined FOXK1 for its role in DNA damage response through the interaction with 53BP1 mainly in soluble fraction.
Project description:UTX is a histone H3 lysine 27 demethylase required for development. However, the mechanisms underlying developmental gene regulation by UTX are unclear. Here, we discovered a molecular interaction between UTX and 53BP1 that regulates gene expression in a human neurogenesis model. Human 53BP1 contains a UTX-binding site that diverges from its mouse homolog by 41%, and our data suggest that the UTX-53BP1 interaction is conserved in primates but not rodents. ChIP-Seq revealed that the genome-wide targets of UTX and 53BP1 overlap by 84%. We used CRISPR-Cas9 to generate mutations of 53BP1 and UTX in human embryonic stem cells, and found that both 53BP1 and UTX are required to promote the expression of hundreds of neurogenic genes during neural differentiation. Further, 53BP1 is required for human neural progenitor differentiation into neurons. Our findings suggest that the UTX-53BP1 interaction controls gene expression important for neural differentiation in humans.
Project description:Absence of 53BP1 influences the profile of DNA rearrangements in B lymphocytes.To determine whether the differences in translocation partner choice were due to differences in transcription, we compared the transcriptome of 53BP1 deficient and wild-type B cells by RNA-Seq and Polymerase II chromatin immunoprecipitation sequencing (ChIP-Seq). Analysis of total mRNA and PolII loading in the presence or absence of 53BP1 in activated B lymphocytes
Project description:During Class Switch Recombination (CSR) B cells replace the Igh Cμ/δ exons with another downstream constant region exon (CH), altering the antibody isotype. CSR occurs through the introduction of AID-mediated double strand break (DSBs) in switch regions and subsequent ligation of broken ends. Here we developed an assay to investigate the dynamics of DSB introduction in individual cells. We demonstrate that the upstream switch region Sμ is always targeted first during recombination and that the mechanism underlying this control relies on 53BP1. Surprisingly, regulation of break order occurs through residual binding of 53BP1 to chromatin before the introduction of damage and independent of its established role in DNA repair. Using chromosome conformation capture we show that 53BP1 mediates changes in chromatin architecture that affect break order. Finally, our results explain how changes in Igh architecture in the absence of 53BP1 could promote inversional rearrangements that compromise CSR. High Resolution 4C was performed in resting and activated B cells using a bait on the Eμ enhancer
Project description:Tudor Interacting Repair Regulator (TIRR) is an RNA-binding protein (RBP) that interacts directly with 53BP1, restricting its access to DNA double-strand breaks (DSBs) and its association with p53. We utilized iCLIP to identify RNAs that directly bind to TIRR within cells, identifying NEAT1_1, the short isoform of the long noncoding RNA NEAT1, as the primary RNA partner. The high affinity of TIRR for NEAT1_1 is due to prevalent G-rich motifs in NEAT1_1. This interaction destabilizes the TIRR/53BP1 complex, promoting 53BP1's function. NEAT1_1 is enriched during the G1 phase of the cell cycle, thereby ensuring that TIRR-dependent inhibition of 53BP1’s function is cell cycle-dependent. TDP-43, an RBP that is implicated in neurodegenerative diseases, modulates the TIRR/53BP1 complex by promoting NEAT1_1 production. Together, we infer that NEAT1_1, and factors regulating NEAT1_1, may impact 53BP1-dependent DNA repair processes, with implications for a spectrum of diseases.
Project description:Double-strand break (DSB) repair choice is greatly influenced by the initial processing of DNA ends. 53BP1 limits the formation of recombinogenic single strand DNA (ssDNA) in BRCA1-deficient cells leading to defects in homologous recombination (HR). However, the exact mechanisms by which 53BP1 inhibits DSB resection remain unclear. Previous studies have identified two potential pathways: protection against exonucleases presumably through the Shieldin (SHLD) complex binding to ssDNA, and localized DNA synthesis through the (CTC1-STN1-TEN1) CST and DNA polymerase alpha (Polα) to counteract resection. We present evidence here that 53BP1-mediated exonuclease protection plays a more significant role than CST/Polα synthesis in countering hyper-resection at DSBs in G1 phase. Using a combinatorial approach of END-seq, SAR-seq, and RPA ChIP-seq, we directly assessed the extent of resection, DNA synthesis, and ssDNA, respectively, at AsiSI-induced DSBs. We show that in the presence of 53BP1, Polα-dependent DNA synthesis reduces the fraction of resected DSBs and the resection lengths. However, in the absence of 53BP1, Polα activity is sustained on ssDNA yet does not substantially counter resection. In contrast, Exo1 nuclease activity is essential for hyperresection in the absence of 53BP1. Thus, 53BP1 inhibits resection mainly through end-protection rather than by promoting fill-in.
Project description:UTX is a histone H3 lysine 27 demethylase required for development. However, the mechanisms underlying developmental gene regulation by UTX are unclear. Here, we discovered a molecular interaction between UTX and 53BP1 that regulates gene expression in a human neurogenesis model. Human 53BP1 contains a UTX-binding site that diverges from its mouse homolog by 41%, and our data suggest that the UTX-53BP1 interaction is conserved in primates but not rodents. ChIP-Seq revealed that the genome-wide targets of UTX and 53BP1 overlap by 84%. We used CRISPR-Cas9 to generate mutations of 53BP1 and UTX in human embryonic stem cells, and found that both 53BP1 and UTX are required to promote the expression of hundreds of neurogenic genes during neural differentiation. Further, 53BP1 is required for human neural progenitor differentiation into neurons. Our findings suggest that the UTX-53BP1 interaction controls gene expression important for neural differentiation in humans.
Project description:UTX is a histone H3 lysine 27 demethylase required for development. However, the mechanisms underlying developmental gene regulation by UTX are unclear. Here, we discovered a molecular interaction between UTX and 53BP1 that regulates gene expression in a human neurogenesis model. Human 53BP1 contains a UTX-binding site that diverges from its mouse homolog by 41%, and our data suggest that the UTX-53BP1 interaction is conserved in primates but not rodents. ChIP-Seq revealed that the genome-wide targets of UTX and 53BP1 overlap by 84%. We used CRISPR-Cas9 to generate mutations of 53BP1 and UTX in human embryonic stem cells, and found that both 53BP1 and UTX are required to promote the expression of hundreds of neurogenic genes during neural differentiation. Further, 53BP1 is required for human neural progenitor differentiation into neurons. Our findings suggest that the UTX-53BP1 interaction controls gene expression important for neural differentiation in humans.
Project description:Double-strand break (DSB) repair choice is greatly influenced by the initial processing of DNA ends. 53BP1 limits the formation of recombinogenic single strand DNA (ssDNA) in BRCA1-deficient cells leading to defects in homologous recombination (HR). However, the exact mechanisms by which 53BP1 inhibits DSB resection remain unclear. Previous studies have identified two potential pathways: protection against exonucleases presumably through the Shieldin (SHLD) complex binding to ssDNA, and localized DNA synthesis through the (CTC1-STN1-TEN1) CST and DNA polymerase alpha (Polα) to counteract resection. We present evidence here that 53BP1-mediated exonuclease protection plays a more significant role than CST/Polα synthesis in countering hyper-resection at DSBs in G1 phase. Using a combinatorial approach of END-seq, SAR-seq, and RPA ChIP-seq, we directly assessed the extent of resection, DNA synthesis, and ssDNA, respectively, at AsiSI-induced DSBs. We show that in the presence of 53BP1, Polα-dependent DNA synthesis reduces the fraction of resected DSBs and the resection lengths. However, in the absence of 53BP1, Polα activity is sustained on ssDNA yet does not substantially counter resection. In contrast, Exo1 nuclease activity is essential for hyperresection in the absence of 53BP1. Thus, 53BP1 inhibits resection mainly through end-protection rather than by promoting fill-in.
Project description:Double-strand break (DSB) repair choice is greatly influenced by the initial processing of DNA ends. 53BP1 limits the formation of recombinogenic single strand DNA (ssDNA) in BRCA1-deficient cells leading to defects in homologous recombination (HR). However, the exact mechanisms by which 53BP1 inhibits DSB resection remain unclear. Previous studies have identified two potential pathways: protection against exonucleases presumably through the Shieldin (SHLD) complex binding to ssDNA, and localized DNA synthesis through the (CTC1-STN1-TEN1) CST and DNA polymerase alpha (Polα) to counteract resection. We present evidence here that 53BP1-mediated exonuclease protection plays a more significant role than CST/Polα synthesis in countering hyper-resection at DSBs in G1 phase. Using a combinatorial approach of END-seq, SAR-seq, and RPA ChIP-seq, we directly assessed the extent of resection, DNA synthesis, and ssDNA, respectively, at AsiSI-induced DSBs. We show that in the presence of 53BP1, Polα-dependent DNA synthesis reduces the fraction of resected DSBs and the resection lengths. However, in the absence of 53BP1, Polα activity is sustained on ssDNA yet does not substantially counter resection. In contrast, Exo1 nuclease activity is essential for hyperresection in the absence of 53BP1. Thus, 53BP1 inhibits resection mainly through end-protection rather than by promoting fill-in.