Abstract
Lectins are widely existed in marine bioresources, and some purified marine lectins were found toxic to cancer cells. In this report, genes encoding Dicentrarchus labrax fucose-binding lectin (DlFBL) and Strongylocentrotus purpuratus rhamnose-binding lectin (SpRBL) were inserted into an adenovirus vector to form Ad.FLAG-DlFBL and Ad.FLAG-SpRBL, which elicited significant in vitro suppressive effect on a variety of cancer cells. Anti-apoptosis factors Bcl-2 and XIAP were determined to be downregulated by Ad.FLAG-DlFBL and Ad.FLAG-SpRBL. Subcellular localization studies showed that DlFBL but not SpRBL widely distributed in membrane systems. Both DlFBL and SpRBL were shown associated with protein arginine methyltransferase 5 (PRMT5), and PRMT5-E2F-1 pathway was suggested to be responsible for the DlFBL and SpRBL induced apoptosis. Further investigations revealed that PRMT5 acted as a common binding target for various exogenous lectin and non-lectin proteins, suggesting a role of PRMT5 as a barrier for foreign gene invasion. The cellular response to exogenous lectins may provide insights into a novel way for cancer gene therapy.
Lectins are carbohydrate-binding proteins that bind reversibly with mono- or oligosaccharide with high specificity and affinity, thus providing biological recognition molecules for a variety of cell types, including hematopoietic cell subpopulations1, pluripotent stem cells2, and various cancer cells3,4,5,6. In marine bioresources, lectins are widely existed in bacteria, algae, invertebrate animals, and fishes, which could be mainly classified into C-type lectins, galectins, F-type lectins, and rhamnose-binding lectins7.
F-type lectins, or fucolectins, recognize fucose and have diversified biological functions in marine animals8,9. Previously, an F-type lectin was purified from the serum of sea bass Dicentrarchus labrax10, which was further cloned, sequenced, and named as Dicentrarchus labrax fucose-binding lectin (DlFBL)11. The molecular property of DlFBL showed two tandem carbohydrate-recognition domains displaying F-type sequence motif. In situ hybridization showed that DlFBL distributed in hepatocytes and intestinal cells, as well as in embryonic yolk residues during fish ontogeny12. The function of DlFBL in Dicentrarchus labrax has been linked to enhancing the phagocytosis of microorganisms by macrophages11.
Rhamnose-binding lectins (RBLs) are a family of animal lectins showing L-rhamnose binding activity and mainly locate in fish reproductive tissues such as eggs and ovaries, as well as immune systems including mucus and blood cells7,13,14,15,16. As unique structural motifs, the carbohydrate recognition domains of RBLs (RBL-CRDs) are responsible for sugar binding, and have been found widely distributed in proteins in almost all animals7. Diversified functions of RBLs have been found. RBLs in Botryllus schlosseri showed immune roles through stimulating phagocytic cells to produce more reactive oxygen species and phagocytose foreign particles, as well as inducing cytotoxic morula cells to secret more cytokines17. In addition to rhamnose binding, some RBLs such as sweet fish lectin (SFL), Silurus asotus lectin (SAL), and chum salmon lectins (CSLs) showed specific binding affinity with globotriaosylceramide (Gb3), which is also known as the receptor for various toxins such as Shiga toxin13,18,19. The binding of RBLs to cell surface Gb3 has been shown to induce a variety of biological functions, which include inducing apoptosis to cancer cells20, causing disappearance of heat shock protein 70 from cell membrane21, as well as stimulating cytokine production from macrophages and enhancing phagocytosis22.
We previously delivered a plant gene encoding mannose binding lectin Pinellia pedatisecta agglutinin (PPA) into a variety of cancer cells through an adenovirus vector and achieved significant anti-proliferative effect. The exogenously expressed PPA was shown to induce cancer cell death through interacting with the methylosome that contains protein arginine methyltransferase 5 (PRMT5) and methylosome protein 50 (MEP50)23. Based on these findings, we proposed that lectins widely existed in the natural world may harbor a reservoir of cytotoxic genes against various cancer cells. In this study, genes encoding marine lectins DlFBL and sea urchin Strongylocentrotus purpuratus rhamnose-binding lectin (SpRBL) were inserted into a replication-deficient adenovirus vector to generate recombinant adenoviruses Ad.FLAG-DlFBL and Ad.FLAG-SpRBL. The Ad.FLAG-DlFBL and Ad.FLAG-SpRBL induced cytotoxicity and the underlying mechanism were analyzed.
Results
A replication-deficient adenovirus vector was engineered to carry genes encoding FLAG-tagged DlFBL and SpRBL, forming adenoviruses Ad.FLAG-DlFBL and Ad.FLAG-SpRBL. To evaluate the anti-proliferative effect of exogenous DlFBL and SpRBL, various cancer cells including hepatocellular carcinoma cell lines Hep3B and BEL-7404, lung cancer cell lines A549, and colorectal carcinoma cell line SW480 were treated with Ad.FLAG-DlFBL and Ad.FLAG-SpRBL, as well as the control adenovirus Ad.FLAG. As compared to Ad.FLAG, Ad.FLAG-DlFBL and Ad.FLAG-SpRBL significantly suppressed the in vitro proliferation of these cancer cells, as determined by MTT assay (Fig. 1a). The suppressive effect of Ad.FLAG-DlFBL and Ad.FLAG-SpRBL on cancer cells showed both time and dose dependant manner. Furthermore, Ad.FLAG-SpRBL elicited a better anti-proliferative effect than Ad.FLAG-DlFBL after 72 h of infection.
To determine the underlying mechanism of the Ad.FLAG-DlFBL and Ad.FLAG-SpRBL induced anti-proliferative effect, Hep3B cells treated with Ad.FLAG-DlFBL, Ad.FLAG-SpRBL, Ad.FLAG or PBS were stained with Annexin V-FITC and propidium iodide (PI), a common method for apoptotic cell staining, and analyzed under a flow cytometer. Fig. 1b showed that Ad.FLAG-DlFBL and Ad.FLAG-SpRBL induced much higher percent of Annexin V+/PI- and Annexin V+/PI+ cells, compared to PBS and Ad.FLAG controls. Significant differences were achieved as shown in Fig. 1c. Results indicate that exogenous expression of DlFBL and SpRBL suppressed cell proliferation through inducing apoptosis.
To further analyze the underlying mechanism of apoptosis induced by Ad.FLAG-DlFBL and Ad.FLAG-SpRBL, Hep3B cells treated with Ad.FLAG-DlFBL, Ad.FLAG-SpRBL, Ad.FLAG, or PBS were lysed, and apoptotic signaling elements were investigated by Western blot. As shown in Fig. 1d, compared to PBS and Ad.FLAG controls, Ad.FLAG-DlFBL and Ad.FLAG-SpRBL did not significantly induced the cleavage of poly (ADP-ribose) polymerase (PARP), a substrate for various caspases, suggesting that Ad.FLAG-DlFBL and Ad.FLAG-SpRBL did not enhanced the activation of caspases. However, Ad.FLAG-DlFBL and Ad.FLAG-SpRBL significantly suppressed levels of anti-apoptosis element including Bcl-2 and X-linked inhibitor of apoptosis protein (XIAP). Data suggested that exogenous expression of DlFBL and SpRBL induced apoptosis in Hep3B cells through downregulating anti-apoptosis factors including Bcl-2 and XIAP.
Intracellular distribution of DlFBL and SpRBL was investigated to further study the underlying mechanism of the apoptosis induced by DlFBL and SpRBL exogenous expression. Cancer cells Hep3B, BEL-7404, or Huh7 were transfected with plasmids pEGFP-DlFBL-C1 or pEGFP-SpRBL-C1, followed by subcellular staining and subsequent observation under a confocal laser scanning microscope. As shown in Fig. 2a–d, DlFBL was shown distributed in various membrane systems, including cell membrane, mitichondria, endoplasmic reticulum (ER), and Golgi apparatus. However, as shown in Fig. 3a–d, the majority of SpRBL did not show co-localization with membrane systems including cell membrane, mitichondria, ER, and Golgi apparatus, which was dramatically different from DlFBL. Interestingly, co-localization of DlFBL and SpRBL with PI high-staining areas in BEL-7404 cells was observed (Fig. 2e and Fig. 3e), suggesting the entrance of DlFBL and SpRBL into the nucleus.
Because nuclear translocation also happened to PPA, which utilized the PRMT5 as a target23, we then analyzed the possible interaction of DlFBL and SpRBL with PRMT5. Plasmids pEGFP-DlFBL-C1 or pEGFP-SpRBL-C1 was co-transfected into Hep3B cells with pdsRed-PRMT5, and the distribution of DlFBL, SpRBL, and PRMT5 was analyzed under a confocal laser scanning microscope. As shown in Fig. 4a and b, obvious co-localization of DlFBL and SpRBL with PRMT5 was determined. Recently, transcription factor E2F-1 was determined to be directly methylated by PRMT5 and acting as a downstream element for PRMT5. We then examined the effect of Ad.FLAG-DlFBL and Ad.FLAG-SpRBL infection on E2F-1 levels. As shown in Fig. 4c, either Ad.FLAG-DlFBL or Ad.FLAG-SpRBL treatment significantly downregulated E2F-1 levels, as compared to PBS and Ad.FLAG controls. Data suggested that the PRMT5-E2F-1 pathway was involved in the DlFBL and SpRBL induced apoptosis.
We then asked whether PRMT5 acts as a common binding target for various exogenous lectins. Genes encoding Haliotis discus discus sialic acid binding lectin (HddSBL), N-acetyl-D-glucosamine binding Ulva pertusa lectin 1 (UPL1), mannose binding Pinellia pedatisecta agglutinin (PPA), as well as a non-lectin protein Equinatoxin II S105-P142 fragment EqtII (S105-P142), were inserted into pEGFP-C1 plasmid, to form pEGFP-HddSBL-C1, pEGFP-UPL1-C1, pEGFP-PPA-C1, and pEGFP-EqtII (S105-P142)-C1, followed by co-transfection into BEL-7404 and Hep3B cells with pdsRed-PRMT5. A confocal laser scanning microscopy showed that not only lectins including HddSBL, UPL1, and PPA (Fig. 4d), but also non-lectin EqtII (S105-P142) fragment (Fig. 4e), were found co-localized with PRMT5. Data suggested that PRMT5 may form a common binding target for a variety of foreign lectin and non-lectin proteins.
Discussion
We reported here that DlFBL and SpRBL distributed differently in cell membrane and cytoplasm. Since lectins are carbohydrate-specific proteins, the differed distribution of these two lectins may suggest differed glycosylation pattern of various membrane systems. Glycans are linked and modified to proteins and lipids by glycosyltransferases and glycosidases in secretory pathways, which play important roles in regulating cell adhesion, molecular trafficking, and signal transduction24. L-fucose is a common component of N- and O-linked glycans and glycolipids in mammalian cells, and frequently exists as terminal residues of glycan structures25. Therefore, membrane exposed fucose may provide recognition site for DlFBL, thus resulting in a wide distribution of DlFBL as shown in our data. On the contrary, poor binding of SpRBL with membrane systems suggest that rhamnose is rarely existed as terminal residues of glycan chains during protein and lipid glycosylation.
Transcription factor E2F-1 has been identified as an activator of cell cycle progression, as well as an apoptosis inducer26. Overexpression of E2F-1 was shown to promote leukemia cell proliferation in a cytokine –independent manner, and a variety of cell cycle dependant cyclins were maintained by E2F-1 without cytokine stimulation27. As a growth-promoting factor, E2F-1 was shown to be associated with adverse prognosis in non-small cell lung cancer28. In contrast, E2F-1 induced cell apoptosis through cooperation with either p5329 or p7330. In response to DNA damage, E2F-1 was activated by Chk2 and led to apoptosis31. Recently, E2F-1 was determined to be a direct substrate for PRMT1 and PRMT532,33, and E2F-1 methylated by PRMT1 augmented cell apoptosis, whereas E2F-1 methylated by PRMT5 favored cell proliferation33, suggesting a key role of differed arginine methylation in determining E2F-1 biological activities. In our data, both DlFBL and SpRBL were found associated with PRMT5, and the expression levels of E2F-1 were downregulated by DlFBL and SpRBL. Furthermore, the expression of DlFBL and SpRBL also suppressed the levels of anti-apoptotic factors Bcl-2 and XIAP. As E2F-1 has been shown to bind to the promoter of Bcl-2 and positively regulate Bcl-2 expression34, our results suggest that the association of exogenous DlFBL and SpRBL with PRMT5 may alter the function of PRMT5 and then the downstream events, the methylation pattern of E2F-1 and decreased levels of E2F-1. The suppressed E2F-1 may subsequently result in a downregulation of apoptosis inhibitors such as Bcl-2 and XIAP, which finally led to cell apoptosis. Therefore, the PRMT5-E2F-1-Bcl-2 pathway was suggested to be the target for the exogenous DlFBL and SpRBL induced apoptosis.
PRMT5, a type II protein arginine methyltransferase, has multiple roles involved in cell differentiation, proliferation, survival, as well as tumorigenesis, through acting on a variety of substrates. PRMT5 methylates histone H4R3, which recruits DNA methyltransferase 3A, resulting in gene silencing35. Arginine methylation by PRMT5 enhances NF-κB p65 subunit activation and drives gene expression including many cytokines and chemokines36. In addition to E2F-1 stated above, HOXA9 is another transcription factor methylated by PRMT5, which has been shown involved in E-selectin induction and endothelial cell inflammatory response37. The substrate specificity of PRMT5 was suggested to be dependant on interactors that PRMT5 associated with38,39,40,41. We previously demonstrated that PRMT5 was co-precipitated with exogenous mannose-binding lectin PPA23. Here, we further identified that PRMT5 acted as a common binding target for various exogenous lectins, including DlFBL, SpRBL, PPA, HddSBL, and UPL1, suggesting a complicated glycosylation pattern of PRMT5 complex. The sugar decoration may be responsible for the wide interaction of PRMT5 complex with various endogenous and exogenous proteins. Second, in addition to lectins, non-lectin protein EqtII S105-P142 fragment was also found associated with PRMT5, suggesting that PRMT5 may play an important role as a mediator to interact with exogenous proteins. Taking into consideration the fact that Hep3B cells infected with Ad.FLAG-DlFBL or Ad.FLAG-SpRBL finally underwent apoptosis, we propose here that PRMT5 may play a role as a sensor for the expression of invaded foreign genes, and subsequently affect E2F-1-Bcl-2 pathway to initiate cell apoptosis, thus forming a barrier for foreign gene sustaining.
We show here that the exogenous expression of DlFBL and SpRBL induced apoptosis and suppressed cancer cell proliferation in vitro. PRMT5 acted as a common binding target for various exogenous lectin or non-lectin proteins. Data suggest that the delivery of genes encoding DlFBL and SpRBL lectins may be a novel strategy to induce cancer cell apoptosis. Further cancer-specific controlling of DlFBL and SpRBL expression may provide insights into a novel way for cancer gene therapy.
Methods
Cell culture and transfection
Heptocellulart carcinoma cell lines Hep3B, Huh7, and BEL-7404, lung cancer cell lines A549, and colorectal carcinoma cell line SW480 were obtained from American Type Culture Collection (Rockville, MD, USA). Cells were maintained in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum, 1% penicillin/streptomycin solution, and 1% L-Glutamine. Appropriate amounts of plasmids were transfected into cells by Thermo Scientific TurboFect Transfection Reagent (Thermo Fisher Scientific Inc, Canada) following the manufacturer's instruction.
Plasmid construction
The plasmid pGH-genes carrying DNA sequences encoding Dicentrarchus labrax fucose-binding lectin (DIFBL, GenBank accession number: EU877448), Strongylocentrotus purpuratus rhamnose-binding lectin (SpRBL, GenBank accession number: LOC100892700), Haliotis discus discus sialic acid binding lectin (HddSBL, GenBank accession no. EF103404), Ulva pertusa lectin 1 (UPL1, GenBank accession no. AY433960) were purchased from Shanghai Generay Biotech Co., Ltd, China. The sequences were cut with XhoI, and then inserted into the corresponding site of pEGFP-C1 to form plasmids pEGFP-gene-C1.
Adenoviral construction
The FLAG tagged sequences of DlFBL and SpRBL were amplified from pGH-DIFBL and pGH-SpRBL through polymerase chain reaction. The products were inserted with pCA13 to form pCA13-FLAG-DlFBL and pCA13-FLAG-SpRBL. The expression cassettes of FLAG-DlFBL and FLAG-SpRBL were digested from plasmids pCA13-FLAG-DlFBL and pCA13-FLAG-SpRBL with BglII and inserted into the corresponding site of plasmid pShuttle, forming plasmids pShuttle-FLAG-DlFBL and pShuttle-FLAG-SpRBL, which were subsequently transformed into strain BJ5183. Viral genomes of Ad.FLAG-DlFBL and Ad.FLAG-SpRBL were generated through homologous recombination of pShuttle-FLAG-DlFBL and pShuttle-FLAG-SpRBL with viral skeleton plasmid pAdEasy-1, and transfected into 293A cells after linearized by PacI. Adenoviruses Ad.FLAG-DlFBL and Ad.FLAG-SpRBL were then produced and virus titers were determined by Titer-EZ adenoviral titer detection Reagent (Shang Hai SBO Medical Biotechnology CO., Ltd, Shanghai, China) following the manufacturer's instruction.
Subcellular staining and colocalization study
ER-Tracker Red, Golgi-Tracker Red, propidium iodide (PI), and DiI were purchased from Beyotime Institute of Biotechnology (Shanghai, China). Mito Tracker Red Mitochondrion-Selective Probe was purchased from Invitrogen (Grand Island, NY, USA). Cells were plated on cover glass bottom dish (35 mm) at 1 × 105 per dish one day before transfection with plasmids. Cells were then transfected with plasmids as previously stated for 24 h or 48 h, followed by staining with ER-Tracker Red, Golgi-Tracker Red, Mito Tracker Mitochondrion Selective Probes, PI, or DiI followed by observation under a confocal laser scanning microscope (Nikon, Inc., Japan).
Cytotoxicity detection and Flow cytometry assay
Cells were plated on 96-well plates at 5 × 103 per well one day before infected with adenoviruses. Then cells were infected with adenoviruses at corresponding multiplicity of infections (MOI) for 48 h, 72 h, or 96 h. The cytotoxicity detection assay was carried out as the procedure of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Meanwhile, cells were plated on 6-well plates at 3 × 105 per well one day before infected with adenoviruses. Then cells were collected to detect apoptosis by Annexin V-FITC Apoptosis Detection Kit (KeyGEN Biotech Co., Ltd, Nanjing, China) following the manufacturer's instruction, followed by analyzing under a BD FACSAria flow cytometry (BD Biosciences, San Jose, CA, USA).
Western blotting analysis
The cell extracts were subjected to SDS-PAGE and electroblotted onto nitrocellulose membranes. The membranes were then blocked with Tris-buffered saline and Tween 20 contaning 5% of bovine serum albumin at room temperature for 2 h and incubated with corresponding antibodies overnight at 4°C. The membranes were washed and incubated with appropriate dilution of IRDye 800 donkey anti-mouse IgG or IRDye 700 donkey anti-rabbit IgG (LI-COR, Inc., Lincoln, NA, USA) for 1 h at room temperature. After washing with Tris-buffered saline, the membranes were then analyzed by an Odyssey Infrared Imaging System (LI-COR, Inc.).
The rabbit anti-PARP (H250) antibody was purchased from Santa Cruz biotechnology Inc. (Santa Cruz, CA, USA). Rabbit anti-XIAP antibody was purchased from Epitomics (Burlingame, CA, USA). Rabbit anti-GAPDH antibody and rabbit anti-Bcl-2 antibody were purchased from Cell Signaling Technology Inc. (Danvers, MA, USA).
Author Contributions
G.L. designed experiments. L.W., X.Y., X.D., L.C. performed experiments. G.L. conceived data and wrote the manuscript.
Supplementary Material
References
- Sharon N. Lectins: carbohydrate-specific reagents and biological recognition molecules. J Biol Chem 282, 2753–2764 (2007). [DOI] [PubMed] [Google Scholar]
- Toyoda M. et al. Lectin microarray analysis of pluripotent and multipotent stem cells. Genes Cells 16, 1–11 (2011). [DOI] [PubMed] [Google Scholar]
- Chen K. et al. Pinellia pedatisecta agglutinin targets drug resistant K562/ADR leukemia cells through binding with sarcolemmal membrane associated protein and enhancing macrophage phagocytosis. PLoS ONE 8, e74363 (2013). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Xu Z. et al. Comparative glycoproteomics based on lectins affinity capture of N-linked glycoproteins from human Chang liver cells and MHCC97-H cells. Proteomics 7, 2358–2370 (2007). [DOI] [PubMed] [Google Scholar]
- Zhu J., He J., Liu Y., Simeone D. M. & Lubman D. M. Identification of glycoprotein markers for pancreatic cancer CD24+CD44+ stem-like cells using nano-LC-MS/MS and tissue microarray. J Proteome Res 11, 2272–2281 (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shi Y. Q., He Q., Zhao Y. J., Wang E. H. & Wu G. P. Lectin microarrays differentiate carcinoma cells from reactive mesothelial cells in pleural effusions. Cytotechnology (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ogawa T., Watanabe M., Naganuma T. & Muramoto K. Diversified carbohydrate-binding lectins from marine resources. J Amino Acids 2011, 838914 (2011). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Odom E. W. & Vasta G. R. Characterization of a binary tandem domain F-type lectin from striped bass (Morone saxatilis). J Biol Chem 281, 1698–1713 (2006). [DOI] [PubMed] [Google Scholar]
- Cammarata M. et al. Isolation and characterization of a fish F-type lectin from gilt head bream (Sparus aurata) serum. Biochim Biophys Acta 1770, 150–155 (2007). [DOI] [PubMed] [Google Scholar]
- Cammarata M., Vazzana M., Chinnici C. & Parrinello N. A serum fucolectin isolated and characterized from sea bass Dicentrarchus labrax. Biochim Biophys Acta 1528, 196–202 (2001). [DOI] [PubMed] [Google Scholar]
- Salerno G. et al. F-type lectin from the sea bass (Dicentrarchus labrax): purification, cDNA cloning, tissue expression and localization, and opsonic activity. Fish Shellfish Immunol 27, 143–153 (2009). [DOI] [PubMed] [Google Scholar]
- Parisi M. G. et al. A serum fucose-binding lectin (DlFBL) from adult Dicentrarchus labrax is expressed in larva and juvenile tissues and contained in eggs. Cell Tissue Res 341, 279–288 (2010). [DOI] [PubMed] [Google Scholar]
- Watanabe Y. et al. Isolation and characterization of l-rhamnose-binding lectin, which binds to microsporidian Glugea plecoglossi, from ayu (Plecoglossus altivelis) eggs. Dev Comp Immunol 32, 487–499 (2008). [DOI] [PubMed] [Google Scholar]
- Okamoto M. et al. Tandem repeat L-rhamnose-binding lectin from the skin mucus of ponyfish, Leiognathus nuchalis. Biochem Biophys Res Commun 333, 463–469 (2005). [DOI] [PubMed] [Google Scholar]
- Tateno H. et al. Immunohistochemical localization of rhamnose-binding lectins in the steelhead trout (Oncorhynchus mykiss). Dev Comp Immunol 26, 543–550 (2002). [DOI] [PubMed] [Google Scholar]
- Jia W. Z., Shang N. & Guo Q. L. Molecular cloning of rhamnose-binding lectin gene and its promoter region from snakehead Channa argus. Fish Physiol Biochem 36, 451–459 (2010). [DOI] [PubMed] [Google Scholar]
- Franchi N. et al. Immune roles of a rhamnose-binding lectin in the colonial ascidian Botryllus schlosseri. Immunobiology 216, 725–736 (2011). [DOI] [PubMed] [Google Scholar]
- Hosono M. et al. Domain composition of rhamnose-binding lectin from shishamo smelt eggs and its carbohydrate-binding profiles. Fish Physiol Biochem (2013). [DOI] [PubMed] [Google Scholar]
- Kawano T., Sugawara S., Hosono M., Tatsuta T. & Nitta K. Alteration of gene expression induced by Silurus asotus lectin in Burkitt's lymphoma cells. Biol Pharm Bull 31, 998–1002 (2008). [DOI] [PubMed] [Google Scholar]
- Bah C. S. et al. Purification and characterization of a rhamnose-binding chinook salmon roe lectin with antiproliferative activity toward tumor cells and nitric oxide-inducing activity toward murine macrophages. J Agric Food Chem 59, 5720–5728 (2011). [DOI] [PubMed] [Google Scholar]
- Sugawara S. et al. Binding of Silurus asotus lectin to Gb3 on Raji cells causes disappearance of membrane-bound form of HSP70. Biochim Biophys Acta 1790, 101–109 (2009). [DOI] [PubMed] [Google Scholar]
- Watanabe Y. et al. The function of rhamnose-binding lectin in innate immunity by restricted binding to Gb3. Dev Comp Immunol 33, 187–197 (2009). [DOI] [PubMed] [Google Scholar]
- Lu Q. et al. Pinellia pedatisecta agglutinin interacts with the methylosome and induces cancer cell death. Oncogenesis 1, e29 (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ohtsubo K. & Marth J. D. Glycosylation in cellular mechanisms of health and disease. Cell 126, 855–867 (2006). [DOI] [PubMed] [Google Scholar]
- Becker D. J. & Lowe J. B. Fucose: biosynthesis and biological function in mammals. Glycobiology 13, 41R–53R (2003). [DOI] [PubMed] [Google Scholar]
- La Thangue N. B. The yin and yang of E2F-1: balancing life and death. Nat Cell Biol 5, 587–589 (2003). [DOI] [PubMed] [Google Scholar]
- Gala S., Marreiros A., Stewart G. J. & Williamson P. Overexpression of E2F-1 leads to cytokine-independent proliferation and survival in the hematopoietic cell line BaF-B03. Blood 97, 227–234 (2001). [DOI] [PubMed] [Google Scholar]
- Gorgoulis V. G. et al. Transcription factor E2F-1 acts as a growth-promoting factor and is associated with adverse prognosis in non-small cell lung carcinomas. J Pathol 198, 142–156 (2002). [DOI] [PubMed] [Google Scholar]
- Wu X. & Levine A. J. p53 and E2F-1 cooperate to mediate apoptosis. Proc Natl Acad Sci U S A 91, 3602–3606 (1994). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Irwin M. et al. Role for the p53 homologue p73 in E2F-1-induced apoptosis. Nature 407, 645–648 (2000). [DOI] [PubMed] [Google Scholar]
- Stevens C., Smith L. & La Thangue N. B. Chk2 activates E2F-1 in response to DNA damage. Nat Cell Biol 5, 401–409 (2003). [DOI] [PubMed] [Google Scholar]
- Cho E. C. et al. Arginine methylation controls growth regulation by E2F-1. EMBO J 31, 1785–1797 (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Zheng S. et al. Arginine methylation-dependent reader-writer interplay governs growth control by E2F-1. Mol Cell 52, 37–51 (2013). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gomez-Manzano C. et al. Transfer of E2F-1 to human glioma cells results in transcriptional up-regulation of Bcl-2. Cancer Res 61, 6693–6697 (2001). [PubMed] [Google Scholar]
- Zhao Q. et al. PRMT5-mediated methylation of histone H4R3 recruits DNMT3A, coupling histone and DNA methylation in gene silencing. Nat Struct Mol Biol 16, 304–311 (2009). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wei H. et al. PRMT5 dimethylates R30 of the p65 subunit to activate NF-kappaB. Proc Natl Acad Sci U S A 110, 13516–13521 (2013). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bandyopadhyay S. et al. HOXA9 methylation by PRMT5 is essential for endothelial cell expression of leukocyte adhesion molecules. Mol Cell Biol 32, 1202–1213 (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Guderian G. et al. RioK1, a new interactor of protein arginine methyltransferase 5 (PRMT5), competes with pICln for binding and modulates PRMT5 complex composition and substrate specificity. J Biol Chem 286, 1976–1986 (2011). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wilczek C. et al. Protein arginine methyltransferase Prmt5-Mep50 methylates histones H2A and H4 and the histone chaperone nucleoplasmin in Xenopus laevis eggs. J Biol Chem 286, 42221–42231 (2011). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Patel S. R., Bhumbra S. S., Paknikar R. S. & Dressler G. R. Epigenetic mechanisms of Groucho/Grg/TLE mediated transcriptional repression. Mol Cell 45, 185–195 (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gurung B. et al. Menin epigenetically represses Hedgehog signaling in MEN1 tumor syndrome. Cancer Res 73, 2650–2658 (2013). [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.