Project description:Transcriptional repressor Growth factor independence 1 (GFI1) is a key regulator of haematopoiesis. We previously established that the germline variant GFI1-36N promotes acute myeloid leukemia (AML) development, however the mechanism is not full elucidated. Here using multi-omics approach, we show GFI1-36N expression impedes DNA repair in leukemic cells. We demonstrate the presence of GFI1-36N is associated with increased frequency of chromosomal aberrations and mutational burden in murine and human AML cells. In particular, GFI1-36N modulates DNA repair pathways, O6-methylguanine-DNA-methyltransferase (MGMT) and homologous recombination repair (HR). Mechanistically, GFI1-36N exhibits impaired binding to Ndrg1 promoter element compared to GFI1-36S (wild type), causing decreased NDRG1 levels consequently leading to suppression of MGMT expression, imprinted at the transcriptome and proteome, thus leaving the AML cells vulnerable to DNA damaging agents. Targeting MGMT via temozolomide and HR via olaparib caused specifically extensive lethality in in vitro and ex vivo human and AML samples expressing GFI1-36N. Whereas the effects were insignificant on non-malignant GFI1-36S or GFI1-36N cells. Further, mice transplanted with GFI1-36N leukemic cells treated with combination of temozolomide and olaparib had a significantly longer AML-free survival than mice transplanted with GFI1-36S leukemic cells. In summary, we show that GFI1-36N disturbs DNA repair activity via NDRG1-MGMT axis and thus provides critical insights into novel therapeutic option for AML presented with GFI1-36N variant. Key Points Presence of GFI1-36N impedes Homologous DNA and MGMT DNA repair selectively in AML cells via the NDRG1-MGMT axis. Use of temozolomide and olaparib allows selectively targeting GFI1-36N leukemic cells. Introduction Gfi1 is a transcription factor which regulates the development of haematopoietic cells as well as neuronal and intestinal epithelial cells 1-5. We reported that a variant of GFI1, denominated GFI1-36N (characterized by an exchange of serine to asparagine at position 36), has a prevalence of 5-7% in a healthy control population but is found at an increased frequency of 10-15% among MDS and AML patients 6,7. The expression of germline variant GFI1-36N predisposes the carriers to develop de novo AML and MDS and correlates with a poor prognosis 6,7. Recently, we and other showed that malignant cells with GFI1-36N variant have increased H3K9-acetylation at target genes resulting in higher expression of genes required for cell survival and proliferation 8. GFI1 exerts its repressive role by recruiting histone-modifying enzymes (deacetylases HDAC1-3, demethylase LSD1, methyl transferase G9a) and regulates the accessibility of DNA to its target genes such as Hoxa9, Pbx1, Meis1, CSF1 and CSFR1 9-15. We also showed that GFI1 regulates apoptosis through its regulation of p53 in lymphoblastic leukemia 16 and we have demonstrated that GFI1 facilitates DNA repair 17. However, it is not known how these activities are affected in the GFI1-36N variant and whether the ability of GFI1 to regulate DNA repair pathways is maintained and how this might affect the development of myeloid malignancies. In this study, we leveraged multi-omics profiling to gain mechanistic insights into the molecular architecture that drives leukemia in the presence of GFI1-36N. We provide evidence that GFI1-36N interferes with DNA in leukemic myeloid cells, which leads to a higher frequency of genetic aberrations in MDS/AML cells. We also show that GFI1-36N myeloid leukemic cells are more sensitive to targeting MGMT and HR repair deficient cells, which opens a new selective therapeutic window to treat AML/MDS.
Project description:Creatine kinase (CK) is an essential metabolic enzyme mediating creatine/phosphocreatine interconversion and shuttle to replenish ATP for energy needs. Ablation of CK causes deficiency in energy supply that eventually results in reduced muscle burst activity and neurological disorders in mice. Besides the well-established role of CK in energy-buffering, the mechanism underlying non-metabolic function of CK is poorly understood. Here we demonstrate that creatine kinase brain-type (CKB) may function as a protein kinase to regulate BCAR1 Y327 phosphorylation that enhances the association between BCAR1 and RBBP4. Then the complex of BCAR1 and RPPB4 binds to the promoter region of DNA damage repair gene RAD51 and activates its transcription by modulating histone H4K16 acetylation to ultimately promote DNA damage repair. These findings reveal the possible role of CKB independently of its metabolic function and depict the potential pathway of CKB-BCAR1-RBBP4 operating in DNA damage repair.
Project description:Chromatin relaxation is a prerequisite step that allows the DNA repair machinery to access double-strand breaks (DSBs), and local histones around the DNA breaks suffer from prompt acetylation changes. However, an intriguing question remains as to where the large demands of acetyl-CoA is precisely produced promptly. Here, we report that pyruvate dehydrogenase 1α (PDHE1α) catalyzes pyruvate metabolism to provide acetyl-CoA promptly in response to DNA damage. PDHE1α was quickly recruited to chromatin in a PARylation-dependent manner, which further drove acetyl-CoA generation to support local chromatin acetylation around the DSB regions. In turn, this process increased the formation of relaxed chromatin to benefit repair factor loading, thus promoting DSB repair to ultimately maintain genome stability and contribute to the resistance of cancer cells to DNA-damaging treatments in vitro and in vivo. In accordance with this, blocking PARylation-based PDHE1α chromatin recruitment markedly attenuated chromatin relaxation and the DSB repair efficiency, resulting in genome instability and restoration of radiosensitivity. Collectively, these findings reveal an undescribed mechanism that underlies site-directed acetyl-CoA generation involving chromatin-associated PDHE1α and its instrumental function in DNA repair and regulating local chromatin acetylation around DSB sites.
Project description:The eukaryotic RNA processing factor Y14 participates in double-strand break (DSB) repair via its RNA-dependent interaction with the non-homologous end-joining (NHEJ) complex. We identified the long non-coding RNA HOTAIRM1 as a candidate that mediates this interaction. HOTAIRM1 localized to DNA damage sites induced by ionizing radiation. Depletion of HOTAIRM1 delayed the recruitment of DNA damage response and repair factors to DNA lesions and reduced DNA repair efficiency. Identification of the HOTAIRM1 interactome revealed a large set of RNA processing factors including mRNA surveillance factors. The surveillance factors Upf1 and SMG6 localized to DNA damage sites in a HOTAIRM1-dependent manner. Depletion of Upf1 or SMG6 increased the level of DSB-induced non-coding transcripts at damaged sites, indicating a pivotal role for Upf1/SMG6-mediated RNA degradation in DNA repair. We conclude that HOTAIRM1 serves as an assembly scaffold for both DNA repair and RNA processing factors that act in concert to repair DSBs.
Project description:Developing an effective binder for a specific ubiquitin (Ub) chain is a promising approach for modulating various biological processes with potential applications in drug discovery. In this study, we combined the Random Non-standard Peptides Integrated Discovery (RaPID) method and chemical protein synthesis to screen an extended library of macrocyclic peptides against synthetic Lys63-linked Di-Ub. This enabled us to discover a novel binder with low nanomolar affinity and specificity for this particular Ub chain. We further chemically modified the most effective binder to generate next-generation binders. We show that our potent cyclic peptide is cell-permeable and inhibits DNA damage repair, leading to cell cycle arrest and apoptotic cell death. Concordantly, a pulldown experiment with the biotinylated analog of our lead cyclic peptide identified various proteins involved in DNA synthesis and damage repair. Collectively, we established a novel and powerful strategy for selective inhibition of protein-protein interactions associated with Lys63-linked Di-Ub using cyclic peptides. This study offers an advancement in modulating central Ub pathways and provides new opportunities in drug discovery areas associated with Ub signaling.
Project description:Formation of a repair enzyme complex is beneficial to DNA repair. Despite cellular studies showed that mitochondrial DNA polymerase (Pol ) and poly(ADP-ribose) polymerase 1 (PARP1) were found in the same complex along with other mitochondrial DNA repair enzymes and mitochondrial PARP1 level is correlated with mtDNA integrity, the molecular basis for the functional connection between Pol and PARP1 has not been illustrated, because cellular functions of PARP1 in DNA repair are intertwined with metabolism via NAD+ (nicotinamide adenosine dinucleotide), the substrate of PARP1 and a metabolic cofactor. To dissect the direct effect of PARP1 on mtDNA from the secondary perturbation metabolism, we report here biochemical studies that recapitulated Pol PARylation observed in cells, showed that PARP1 regulates Pol activity during DNA repair in a metabolic cofactor NAD+ (nicotinamide adenosine dinucleotide)-dependent manner. In the absence of NAD+, PARP1 completely inhibits Pol, while increasing NAD+ level to physiological concentration enables Pol to resume maximum repair activity. Because cellular NAD+ levels are linked to metabolism and to ATP production via oxidative phosphorylation, our results suggest that mtDNA damage repair is correlated with cellular metabolic state and integrity of the respiratory chain.