Loss of the N-terminal methyltransferase NRMT1 increases sensitivity to DNA damage and promotes mammary oncogenesis.
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ABSTRACT:
SUBMITTER: Bonsignore LA
PROVIDER: S-EPMC4494936 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:FZR1 (fizzy-related protein homolog; also known as CDH1 [cell division cycle 20 related 1]) functions in the cell cycle as a specific activator of anaphase-promoting complex or cyclosome ubiquitin ligase, regulating late mitosis, G1 phase, and activation of the G2-M checkpoint. FZR1 has been implicated as both a tumor suppressor and oncoprotein, and its precise contribution to carcinogenesis remains unclear. Here, we examined the role of FZR1 in tumorigenesis and cancer therapy by analyzing tumor models and patient specimens. In an Fzr1 gene-trap mouse model of B-cell acute lymphoblastic leukemia (B-ALL), mice with Fzr1-deficient B-ALL survived longer than those with Fzr1-intact disease, and sensitivity of Fzr1-deficient B-ALL cells to DNA damage appeared increased. Consistently, conditional knockdown of FZR1 sensitized human B-ALL cell lines to DNA damage-induced cell death. Moreover, multivariate analyses of reverse-phase protein array of B-ALL specimens from newly diagnosed B-ALL patients determined that a low FZR1 protein expression level was an independent predictor of a longer remission duration. The clinical benefit of a low FZR1 expression level at diagnosis was no longer apparent in patients with relapsed B-ALL. Consistent with this result, secondary and tertiary mouse recipients of Fzr1-deficient B-ALL cells developed more progressive and radiation-resistant disease than those receiving Fzr1-intact B-ALL cells, indicating that prolonged inactivation of Fzr1 promotes the development of resistant clones. Our results suggest that reduction of FZR1 increases therapeutic sensitivity of B-ALL and that transient rather than tonic inhibition of FZR1 may be a therapeutic strategy.
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Project description:Protein, DNA, and RNA methyltransferases have an ever-expanding list of novel substrates and catalytic activities. Even within families and between homologs, it is becoming clear the intricacies of methyltransferase specificity and regulation are far more diverse than originally thought. In addition to specific substrates and distinct methylation levels, methyltransferase activity can be altered by complex formation with close homologs. We work with the N-terminal methyltransferase homologs NRMT1 and NRMT2. NRMT1 is a ubiquitously expressed distributive trimethylase. NRMT2 is a monomethylase expressed at low levels in a tissue-specific manner. They are both nuclear methyltransferases with overlapping consensus sequences but have distinct enzymatic activities and tissue expression patterns. Co-expression with NRMT2 increases the trimethylation rate of NRMT1, and here we aim to understand how this occurs. We use analytical ultracentrifugation to show that while NRMT1 primarily exists as a dimer and NRMT2 as a monomer, when co-expressed they form a heterotrimer. We use co-immunoprecipitation and molecular modeling to demonstrate in vivo binding and map areas of interaction. While overexpression of NRMT2 increases the half-life of NRMT1, the converse is not true, indicating that NRMT2 may be increasing NRMT1 activity by stabilizing the enzyme. Accordingly, the catalytic activity of NRMT2 is not needed to increase NRMT1 activity or increase its affinity for less preferred substrates. Monomethylation can also not rescue phenotypes seen with loss of trimethylation. Taken together, these data support a model where NRMT2 expression activates NRMT1 activity, not through priming, but by increasing its stability and substrate affinity.
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Project description:NRMT1 is an N-terminal methyltransferase that methylates histone CENP-A as well as nonhistone substrates. Here, we report the crystal structure of human NRMT1 bound to CENP-A peptide at 1.3 Å. NRMT1 adopts a core methyltransferase fold that resembles DOT1L and PRMT but not SET domain family histone methyltransferases. Key substrate recognition and catalytic residues were identified by mutagenesis studies. Histone peptide profiling revealed that human NRMT1 is highly selective to human CENP-A and fruit fly H2B, which share a common "Xaa-Pro-Lys/Arg" motif. These results, along with a 1.5 Å costructure of human NRMT1 bound to the fruit fly H2B peptide, underscore the importance of the NRMT1 recognition motif.
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Project description:Non-small-cell lung cancer (NSCLC) is a common malignancy with a poor prognosis. Despite progress targeting oncogenic drivers, there are no therapies targeting tumor-suppressor loss. Smad4 is an established tumor suppressor in pancreatic and colon cancer; however, the consequences of Smad4 loss in lung cancer are largely unknown. We evaluated Smad4 expression in human NSCLC samples and examined Smad4 alterations in large NSCLC data sets and found that reduced Smad4 expression is common in human NSCLC and occurs through a variety of mechanisms, including mutation, homozygous deletion and heterozygous loss. We modeled Smad4 loss in lung cancer by deleting Smad4 in airway epithelial cells and found that Smad4 deletion both initiates and promotes lung tumor development. Interestingly, both Smad4(-/-) mouse tumors and human NSCLC samples with reduced Smad4 expression demonstrated increased DNA damage, whereas Smad4 knockdown in lung cancer cells reduced DNA repair and increased apoptosis after DNA damage. In addition, Smad4-deficient NSCLC cells demonstrated increased sensitivity to both chemotherapeutics that inhibit DNA topoisomerase and drugs that block double-strand DNA break repair by non-homologous end joining. In sum, these studies establish Smad4 as a lung tumor suppressor and suggest that the defective DNA repair phenotype of Smad4-deficient tumors can be exploited by specific therapeutic strategies.
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Project description:NRMT (N-terminal regulator of chromatin condensation 1 methyltransferase) was the first eukaryotic methyltransferase identified to specifically methylate the free ?-amino group of proteins. Since the discovery of this N-terminal methyltransferase, many new substrates have been identified and the modification itself has been shown to regulate DNA-protein interactions. Sequence analysis predicts one close human homologue of NRMT, METTL11B (methyltransferase-like protein 11B, now renamed NRMT2). We show in the present paper for the first time that NRMT2 also has N-terminal methylation activity and recognizes the same N-terminal consensus sequences as NRMT (now NRMT1). Both enzymes have similar tissue expression and cellular localization patterns. However, enzyme assays and MS experiments indicate that they differ in their specific catalytic functions. Although NRMT1 is a distributive methyltransferase that can mono-, di- and tri-methylate its substrates, NRMT2 is primarily a monomethylase. Concurrent expression of NRMT1 and NRMT2 accelerates the production of trimethylation, and we propose that NRMT2 activates NRMT1 by priming its substrates for trimethylation.
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Project description:BackgroundReceptor for advanced glycation end products (RAGE) is a multi-ligand transmembrane receptor of the immunoglobulin superfamily. Lysophosphatidic acid (LPA) is a ligand for RAGE and is involved in physiological and pathophysiological conditions including cancer. However, RAGE-LPA axis is unexplored in lung and mammary cancer.MethodsRAGE was silenced in A549, MDA MB-231 and MCF7 using RAGE shRNA. For in vitro tumorigenesis, we performed wound healing, colony formation, cell proliferation and invasion assays. Evaluation of expression of oncogenes, EMT markers and downstream signaling molecules was done by using western blot and immunohistochemistry. For subcellular expression of RAGE, immunofluorescence was done. In vivo tumorigenesis was assessed by intraperitoneal injection of cancer cells in nude mice.ResultsHere we show RAGE mediated profound increase in proliferation, migration and invasion of lung and mammary cancer cells via LPA in Protein kinase B (PKB) dependent manner. LPA mediated EMT transition is regulated by RAGE. In vivo xenograft results show significance of RAGE in LPA mediated lung and mammary tumor progression, angiogenesis and immune cell infiltration to tumor microenvironment.ConclusionOur results establish the significance and involvement of RAGE in LPA mediated lung and mammary tumor progression and EMT transition via RAGE. RAGE-LPA axis may be a therapeutic target in lung and mammary cancer treatment strategies. Video Abstract.
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Project description:C-terminal-truncated hepatitis B virus (HBV) X (HBx) (ctHBX) is frequently detected in hepatocellular carcinoma (HCC) through HBV integration into the host genome. However, the molecular mechanisms underlying ctHBx-associated oncogenic signaling have not yet been clarified. To elucidate the biological role of ctHBx in hepato-oncogenesis, we functionally analyzed ctHBx-mediated regulation of the activin membrane-bound inhibitor bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) through transforming growth factor-? (TGF-?) or ?-catenin (CTNNB1) in HCC cells and in an animal model, and we compared its role to that of the full-length HBx protein. Ectopic ctHBx expression generated more colonies in anchorage-dependent and -independent growth assays than did HBx expression alone. ctHBx downregulated BAMBI to a greater degree than did HBx in HCC cells. HBx activated the Wnt/?-catenin pathway, which positively regulated the BAMBI expression through T-cell factor 1 signaling, whereas ctHBx negatively regulated the Wnt/?-catenin pathway. BAMBI downregulated the ?-catenin and TGF-?1 signaling pathways. TGF-?1 positively regulated BAMBI expression thorough Smad3 signaling. Furthermore, knockdown of BAMBI was more tumorigenic in HCC cells. Therefore, downregulation of both ?-catenin and TGF-?1 signaling by BAMBI might contribute to tumor suppression in mice xenotransplanted with HepG2 or SH-J1 cells. Taken together, ctHBx may have a more oncogenic role than HBx through its inhibition of tumor-suppressive ?-catenin/BAMBI signaling.
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Project description:Evidence of cancer immunosurveillance and immunoediting processes has been primarily demonstrated in mouse models of chemically induced oncogenesis. Although these models are very tractable, they are characterized by high mutational loads that represent a minority of human cancers. In this study, we sought to determine whether cancer immunosurveillance and immunoediting could be demonstrated in a more clinically relevant oncogene-induced model of carcinogenesis, the MMTV-PyMT (PyMT) mammary carcinoma model. This model system in the FVB/NJ strain background was previously used to demonstrate that adaptive immunity had no role in limiting primary cancer formation and in fact promoted metastasis, thus calling into question whether cancer immunosurveillance operated in preventing the development of breast cancer. Our current study in the C57BL/6 strain backgrounds provides a different conclusion, as we report here the existence of an adaptive immunosurveillance of PyMT mammary carcinomas using two independent models of immune deficiency. PyMT mice bred onto a Rag1-/- background or immune suppressed by chronic tacrolimus therapy both demonstrated accelerated development of mammary carcinomas. By generating a bank of cell lines from these animals, we further show that a subset of PyMT cell lines had delayed growth after transplantation into wild-type (WT) syngeneic, but not immune-deficient hosts. This reduced growth rate in immunocompetent animals was characterized by an increase in immune cell infiltration and tissue differentiation. Furthermore, loss of the immune cell infiltration that characterized immunoediting of slow growing cell lines, changed them into fast growing variants capable of progressing in the immunocompetent model. In conclusion, our study provides evidence that immunosurveillance and immunoediting of PyMT-derived cell lines modulate tumor progression in this oncogene-induced model of cancer.
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Project description:Pregnancy reprograms mammary epithelial cells (MECs) to control their responses to pregnancy hormone re-exposure and carcinoma progression. However, the influence of pregnancy on the mammary microenvironment is less clear. Here, we used single-cell RNA sequencing to profile the composition of epithelial and non-epithelial cells in mammary tissue from nulliparous and parous female mice. Our analysis indicates an expansion of γδ natural killer T-like immune cells (NKTs) following pregnancy and upregulation of immune signaling molecules in post-pregnancy MECs. We show that expansion of NKTs following pregnancy is due to elevated expression of the antigen-presenting molecule CD1d on MECs. Loss of CD1d expression on post-pregnancy MECs, or overall lack of activated NKTs, results in mammary oncogenesis. Collectively, our findings illustrate how pregnancy-induced changes modulate the communication between MECs and the immune microenvironment and establish a causal link between pregnancy, the immune microenvironment, and mammary oncogenesis.
| S-EPMC8719356 | biostudies-literature
Project description:Background and purposeSphingosine kinases (SK) catalyse the formation of sphingosine 1-phosphate, which is a key lipid mediator regulating cell responses such as proliferation, survival and migration. Here we have investigated the effect of targeted inhibition of SK-1 on cell damage and elucidated the mechanisms involved.Experimental approachThree human carcinoma cell lines (colon HCT-116, breast MDA-MB-231, lung NCI-H358) were used, which were either transduced with shRNA constructs to deplete SK-1, or treated with a SK-1 inhibitor. Cell growth and viability were assayed by [(3) H]thymidine incorporation and colony formation. Reactive oxygen species (ROS) were measured by fluorescence and apoptosis by annexin V with flow cytometry. Proteins were analysed by Western blotting. DNA damage was induced by doxorubicin.Key resultsKnock-down of SK-1 by shRNA strongly inhibited DNA synthesis and colony formation of carcinoma cells. SK-1 knock-down (SK-1kd) cells revealed dysfunctional extracellular signal-regulated protein kinase and PKB/Akt cascades, and contained increased levels of ROS. After SK-1kd, treatment with doxorubicin increased DNA damage, measured by histone-2AX phosphorylation. Similar effects were found in cells with a SK-1 inhibitor and doxorubicin. The increased damage response in SK-1kd cells was accompanied by greater reduction of DNA synthesis and colony formation, and by more pronounced apoptosis. Addition of a NADPH oxidase inhibitor reduced the increased apoptosis in doxorubicin-treated SK-1kd cells.Conclusions and implicationsSK-1kd in carcinoma cells triggered oxidative stress by increasing intracellular Ros production. Targeted inhibition of SK-1 represents a promising approach to sensitize cells to DNA damage and facilitate apoptosis upon doxorubicin treatment.
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