HMGN2 represses gene transcription via interaction with transcription factors Lef-1 and Pitx2 during amelogenesis.

The chromatin-associated high mobility group protein N2 (HMGN2) cofactor regulates transcription factor activity through both chromatin and protein interactions. Hmgn2 expression is known to be developmentally regulated, but the post-transcriptional mechanisms that regulate Hmgn2 expression and its precise roles in tooth development remain unclear. Here, we demonstrate that HMGN2 inhibits the activity of multiple transcription factors as a general mechanism to regulate early development. Bimolecular fluorescence complementation, pull-down, and coimmunoprecipitation assays show that HMGN2 interacts with the transcription factor Lef-1 through its HMG-box domain as well as with other early development transcription factors, Dlx2, FoxJ1, and Pitx2. Furthermore, EMSAs demonstrate that HMGN2 binding to Lef-1 inhibits its DNA-binding activity. We found that Pitx2 and Hmgn2 associate with H4K5ac and H3K4me2 chromatin marks in the proximal Dlx2 promoter, demonstrating Hmgn2 association with open chromatin. In addition, we demonstrate that microRNAs (miRs) mir-23a and miR-23b directly target Hmgn2, promoting transcriptional activation at several gene promoters, including the amelogenin promoter. In vivo, we found that decreased Hmgn2 expression correlates with increased miR-23 expression in craniofacial tissues as the murine embryo develops. Finally, we show that ablation of Hmgn2 in mice results in increased amelogenin expression because of increased Pitx2, Dlx2, Lef-1, and FoxJ1 transcriptional activity. Taken together, our results demonstrate both post-transcriptional regulation of Hmgn2 by miR-23a/b and post-translational regulation of gene expression by Hmgn2-transcription factor interactions. We conclude that HMGN2 regulates tooth development through its interaction with multiple transcription factors.

The regulatory effect of acetylation of HMGN2 and H3K27 on pyocyanin-induced autophagy in macrophages by affecting Ulk1 transcription.

Pyocyanin (PYO) is a major virulence factor secreted by Pseudomonas aeruginosa, and autophagy is a crucial homeostatic mechanism for the interaction between the pathogens and the host. It remains unknown whether PYO leads to autophagy in macrophages by regulating histone acetylation. The high mobility group nucleosomal binding domain 2 (HMGN2) has been reported to regulate the PYO-induced autophagy and oxidative stress in the epithelial cells; however, the underlying molecular mechanism has not been fully elucidated. In this study, PYO was found to induce autophagy in macrophages, and the mechanism might be correlated with the up-regulation of HMGN2 acetylation (HMGN2ac) and the down-regulation of H3K27 acetylation (H3K27ac) by modulation of the activities of acetyltransferases and deacetylases. Moreover, we further demonstrated that the up-regulated HMGN2ac enhances its recruitment to the Ulk1 promoter, while the down-regulation of H3K27ac reduces its recruitment to the Ulk1 promoter, thereby promoting or inhibiting the transcription of Ulk1. In conclusion, HMGN2ac and H3K27ac play regulatory roles in the PYO-induced autophagy in macrophages.

Prognostic value of HMGN family expression in acute myeloid leukemia.

Aim: The objective of this work was to investigate the prognostic role of the HMGN family in acute myeloid leukemia (AML). Methods: A total of 155 AML patients with HMGN1-5 expression data from the Cancer Genome Atlas database were enrolled in this study. Results: In the chemotherapy-only group, patients with high HMGN2 expression had significantly longer event-free survival (EFS) and overall survival (OS) than those with low expression (all p < 0.05), whereas high HMGN5 expressers had shorter EFS and OS than the low expressers (all p < 0.05). Multivariate analysis identified that high HMGN2 expression was an independent favorable prognostic factor for patients who only received chemotherapy (all p < 0.05). HMGN family expression had no impact on EFS and OS in AML patients receiving allogeneic hematopoietic stem cell transplantation. Conclusion: High HMGN2/5 expression is a potential prognostic indicator for AML.

Transcriptomic analysis of peripheral blood mononuclear cells in head and neck squamous cell carcinoma patients.

OBJECTIVES: To investigate the gene expression profile of peripheral blood mononuclear cells (PBMCs) from head and neck squamous cell carcinoma (HNSCC), including oral cancer (OC) and oropharyngeal cancer (OPC) patients, and compare them with healthy controls (HC). MATERIALS AND METHODS: Transcriptomic analysis of PBMCs was performed by RNA-sequencing. The upregulated candidate genes were selected for validation by quantitative real-time polymerase chain reaction (qPCR). In addition, related plasma protein levels were determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: Three significantly upregulated genes, including high mobility group nucleosomal binding domain 2 (HMGN2), folate receptor gamma (FOLR3), and amphiregulin (AREG), were selected. In the first cohort, the results showed that only HMGN2 expression was significantly increased in OC patients. In the larger sample size, the overall results demonstrated that HMGN2 expression had a tendency to increase in both OC and OPC patients compared with HC. Interestingly, the plasma HMGN2 (HMG-17) protein level exhibited the same trend as that observed at the transcriptional level. CONCLUSION: HMGN2 expression and plasma HMG-17 (HMGN2 protein) were increased in both cancer patients compared with HC. This gene may be important for further functional studies in the PBMCs of HNSCC patients.

High mobility group nucleosomal binding 2 reduces integrin α5/ß1-mediated adhesion of Klebsiella pneumoniae on human pulmonary epithelial cells via nuclear factor I.

It has been reported that high mobility group nucleosomal binding domain 2 (HMGN2) is a nucleus-related protein that regulates gene transcription and plays a critical role in bacterial clearance. An elevated level of HMGN2 reduced integrin α5/ß1 expression of human pulmonary epithelial A549 cells was demonstrated during Klebsiella pneumoniae infection, thus weakening bacterial adhesion and invasion. However, the mechanism by which HMGN2 regulates integrin expression remains unclear. This study found that a transcription factor-nuclear factor I (NFI), which serves as the potential target of HMGN2 regulated integrin expression. The results showed that HMGN2 was able to promote NFIA and NFIB expression by increasing H3K27 acetylation of NFIA/B promoter regions. The integrin α5/ß1 expression was significantly enhanced by knockdown of NFIA/B via a siRNA approach. Meanwhile, NFIA/B silence could also compromise the inhibition effect of HMGN2 on the integrin α5/ß1 expression. Mechanistically, it was demonstrated that HMGN2 facilitated the recruitment of NFI on the promoter regions of integrin α5/ß1 according to the chromatin immunoprecipitation assay. In addition, it was further demonstrated that the knockdown of NFIA/B induced more adhesion of Klebsiella pneumoniae on pulmonary epithelial A549 cells, which could be reversed by the application of an integrin inhibitor RGD. The results revealed a regulatory role of HMGN2 on the transcription level of integrin α5/ß1, indicating a potential treatment strategy against Klebsiella pneumoniae-induced infectious lung diseases.

HMGN2 regulates non-tuberculous mycobacteria survival via modulation of M1 macrophage polarization.

Non-tuberculous mycobacteria (NTM), also known as an environmental and atypical mycobacteria, can cause the chronic pulmonary infectious diseases. Macrophages have been suggested as the main host cell to initiate the innate immune responses to NTM infection. However, the molecular mechanism to regulate the antimicrobial immune responses to NTM is still largely unknown. Current study showed that the NTM clinical groups, Mycobacterium abscessus and Mycobacterium smegmatis, significantly induced the M1 macrophage polarization with the characteristic production of nitric oxide (NO) and marker gene expression of iNOS, IFNγ, TNF-α, IL1-ß and IL-6. Interestingly, a non-histone nuclear protein, HMGN2 (high-mobility group N2), was found to be spontaneously induced during NTM-activated M1 macrophage polarization. Functional studies revealed that HMGN2 deficiency in NTM-infected macrophage promotes the expression of M1 markers and the production of NO via the enhanced activation of NF-κB and MAPK signalling. Further studies exhibited that HMGN2 knock-down also enhanced IFNγ-induced M1 macrophage polarization. Finally, we observed that silencing HMGN2 affected the survival of NTM in macrophage, which might largely relevant to enhanced macrophage polarization into M1 phenotype under the NTM infection. Collectively, current studies thus suggested a novel function of HMGN2 in regulating the anti-non-tuberculous mycobacteria innate immunity of macrophage.

High-mobility group protein N2 induces autophagy by activating AMPK/ULK1 pathway and thereby boosts UPEC proliferation within bladder epithelial cells.

Urinary tract infection is one of the most common bacterial infections which is mainly caused by Escherichia coli (UPEC). Autophagy plays a key role in immune response to eliminate invading pathogens. Exploring the effect of autophagy on UPEC infection and the molecular mechanisms will be benefit for the treatment of urinary tract infection. High-mobility group protein N2 (HMGN2), a highly conserved nuclear protein and an antibacterial peptide, has been associated with bacterial infection induced immune response; however, whether this function is due to the regulation of autophagy remains unclear. In this study, we demonstrate for the first time that HMGN2 is upregulated in UPEC infection of bladder epithelial cell line 5637 (BEC 5637). Furthermore, HMGN2 enhances autophagy in BEC 5637 via activation of AMPK and ULK1, whereas UPEC suppresses autophagy. In addition, the enhanced autophagy activity by HMGN2 overexpression or rapamycin boosts the proliferation of UPEC J96 in BEC 5637. In summary, our data indicate that HMGN2 activates autophagy via AMPK/ULK1 pathway which can be utilized by UPEC J96 for their proliferation within bladder epithelial cells.

Histone H1 and Chromosomal Protein HMGN2 Regulate Prolactin-induced STAT5 Transcription Factor Recruitment and Function in Breast Cancer Cells.

The hormone prolactin (PRL) contributes to breast cancer pathogenesis through various signaling pathways, one of the most notable being the JAK2/signal transducer and activator of transcription 5 (STAT5) pathway. PRL-induced activation of the transcription factor STAT5 results in the up-regulation of numerous genes implicated in breast cancer pathogenesis. However, the molecular mechanisms that enable STAT5 to access the promoters of these genes are not well understood. Here, we show that PRL signaling induces chromatin decompaction at promoter DNA, corresponding with STAT5 binding. The chromatin-modifying protein high mobility group nucleosomal binding domain 2 (HMGN2) specifically promotes STAT5 accessibility at promoter DNA by facilitating the dissociation of the linker histone H1 in response to PRL. Knockdown of H1 rescues the decrease in PRL-induced transcription following HMGN2 knockdown, and it does so by allowing increased STAT5 recruitment. Moreover, H1 and STAT5 are shown to function antagonistically in regulating PRL-induced transcription as well as breast cancer cell biology. While reduced STAT5 activation results in decreased PRL-induced transcription and cell proliferation, knockdown of H1 rescues both of these effects. Taken together, we elucidate a novel mechanism whereby the linker histone H1 prevents STAT5 binding at promoter DNA, and the PRL-induced dissociation of H1 mediated by HMGN2 is necessary to allow full STAT5 recruitment and promote the biological effects of PRL signaling.

Evidence For Hmgn2 Involvement in Mouse Embryo Implantation and Decidualization.

BACKGROUND/AIMS: Hmgn2 is involved in regulating embryonic development, but its physiological function during embryo implantation and decidualization remains unknown. METHODS: In situ hybridization, real-time PCR, RNA interference, gene overexpression and MTS assay were used to examine the expression of Hmgn2 in mouse uterus during the pre-implantation period and explore its function and regulatory mechanisms in epithelial adhesion junction and stromal cell proliferation and differentiation. RESULTS: Hmgn2 was primarily accumulated in uterine luminal epithelia on day 4 of pregnancy and subluminal stromal cells around the implanting blastocyst at implantation sites on day 5. Similar results were observed during delayed implantation and activation. Meanwhile, Hmgn2 expression was visualized in the decidua. In uterine epithelial cells, silencing of Hmgn2 by specific siRNA reduced the expression of adhesion molecules Cdh1, Cdh2 and Ctnnb1 and enhanced the expression of Muc1, whereas constitutive activation of Hmgn2 exhibited the opposite effects, suggesting a role for Hmgn2 in attachment reaction during embryo implantation. Estrogen stimulated the expression of Hmgn2 in uterine epithelia, but the stimulation was abrogated by ER antagonist ICI 182,780. Further analysis evidenced that attenuation of Hmgn2 might eliminate the regulation of estrogen on the expression of Cdh1, Cdh2 and Ctnnb1. In uterine stromal cells, progesterone induced the accumulation of Hmgn2 which advanced the expression of Prl8a2 and Prl3c1, two well-known differentiation markers for decidualization, but did not affect the proliferation of stromal cells. Knockdown of Hmgn2 blocked the progesterone-induced differentiation of uterine stromal cells. Moreover, Hmgn2 might serve as an intermediate to mediate the regulation of progesterone on Hand2. CONCLUSION: Hmgn2 may play an important role during embryo implantation and decidualization.

High mobility group nucleosomal binding domain 2 (HMGN2) SUMOylation by the SUMO E3 ligase PIAS1 decreases the binding affinity to nucleosome core particles.

High mobility group nucleosomal binding domain 2 (HMGN2) is a small and unique non-histone protein that has many functions in a variety of cellular processes, including regulation of chromatin structure, transcription, and DNA repair. In addition, it may have other roles in antimicrobial activity, cell homing, and regulating cytokine release. Although the biochemical properties of HMGN2 protein are regulated by acetylation and phosphorylation, it is not yet known whether HMGN2 activity can also be regulated by SUMOylation. In this study, we demonstrated for the first time that HMGN2 is modified by covalent attachment of small ubiquitin-related modifier 1 (SUMO1) by pro-inflammatory signal and identified the major SUMOylated lysine residues that localize to the HMGN2 nucleosome-binding domain at Lys-17 and Lys-35. SENP1 can deSUMOylate SUMOylated HMGN2, and PIAS1 is the E3 ligase responsible for SUMOylation of HMGN2. Finally, using SUMO1-conjugated HMGN2 purified from a basal SUMOylation system in Escherichia coli, we demonstrated that SUMOylated HMGN2 has decreased the binding affinity to nucleosome core particles in comparison to unSUMOylated HMGN2. These observations potentially provide new perspectives for understanding the functions of HMGN2 in inflammatory reaction.

HMGN2 and Histone H1.2: potential targets of a novel probiotic mixture for seasonal allergic rhinitis.

Background: Allergic rhinitis (AR) is a common nasal inflammatory disorder that severely affects an individual's quality of life (QoL) and poses a heavy financial burden. In addition to routine treatments, probiotic intervention has emerged as a promising strategy for preventing and alleviating allergic diseases. The main objective of this study was to determine the effect of a novel multi-strain probiotic mixture on AR symptoms and investigate potential targets underlying the probiotic intervention. Methods: A randomized, double-blind, placebo-controlled clinical study was conducted on AR patients who were allergic to autumnal pollens (n = 31). Placebo or a novel probiotic mixture, composed of Lactobacillus rhamnosus (L. rhamnosus) HN001, L. acidophilus NCFM, Bifidobacterium lactis (B. lactis) Bi-07, L. paracasei LPC-37, and L. reuteri LE16, was administered after 2 months. The therapeutic efficacy was evaluated by a symptom assessment scale. Before and during the pollen season, blood samples were collected, and peripheral blood mononuclear cells (PBMCs) were isolated for further tandem mass tags (TMTs)-based quantitative proteomic analyses. Potential targets and underlying pathological pathways were explored using bioinformatics methods. Results: During the pollen season, the rhinoconjunctivitis symptom score of participants who were administered probiotics (probiotic group, n = 15) was significantly lower than those administered placebo (placebo group, n = 15) (P = 0.037). The proteomic analyses identified 60 differentially expressed proteins (DEPs) in the placebo group, and subsequent enrichment analyses enriched a series of pathways and biological processes, including signaling pathways of inflammation, coagulation cascade, lipid, carbohydrate and amino acid metabolic pathways, and transcription and translation processes. Least Absolute Shrinkage and Selection Operator (LASSO) regression extracted five main elements, namely, GSTO1, ATP2A2, MCM7, PROS1, and TRIM58, as signature proteins. A total of 17 DEPs were identified in the probiotic group, and there was no pathway enriched. Comparison of DEPs in the two groups revealed that the expression levels of the high-mobility group nucleosome-binding domain-containing protein 2 (HMGN2) and Histone H1.2 presented an opposite trend with different interventions. Conclusion: Our data showed that AR symptoms alleviated after treatment with the novel multi-strain probiotic mixture, and the proteomic analyses suggested that HMGN2 and Histone H1.2 might be targets of probiotic intervention for seasonal AR.

Recombinant jurkat cells (HMGN2-T cells) secrete cytokines and inhibit the growth of tumor cells.

High Mobility Group Chromosomal Protein N2 (HMGN2) can recognize tumor cells and enhance the anti-tumor effect of immune cells. This study aimed to establish a lentiviral vector of recombinant HMGN2 gene, establish recombinant T cells (HMGN2-T cells), and observe their anti-tumor effects. Total RNA was isolated from peripheral blood mononuclear cells. HMGN2, cluster of differentiation (CD) 8 A, CD28, CD137, and CD3ζ genes were amplified and connected. Jurkat cells were transfected with the recombinant lentivirus vector. The viability, apoptosis, and cell cycle of HMGN2-T cells were detected using Cell Counting Kit-8 assay and flow cytometry. The co-culture was performed by adding HMGN2-T cells to tumor cells with different effect-to-target (E:T) ratios. The cytotoxic activity was measured by lactate dehydrogenase (LDH) releasing assay. The sequences of HMGN2, CD8A, CD28, CD137, and CD3ζ gene plasmids were confirmed using gene sequencing. After the lentiviral transfection for 72 h, green fluorescence cells (HMGN2-T cells) could be seen. Cell viability and apoptosis were increased in HMGN2-T cells. The cytokine levels of interleukin 2 (IL-2) and tumor necrosis factor α (TNF-α) increased in cell supernatants of HMGN2-T cells. The percentage of G0/G1 phase cells was lower, the rate of S phase cells was higher in HMGN2-T cells than control cells. The co-culture of HMGN2-T cells and tumor cells could promote the cytokines' release. The LDH level was increased with the elevation of E:T ratios. In conclusion, the HMGN2-T cells were well-established and have the effect of secreting cytokines and killing tumor cells.

Expression of HMGB1 and HMGN2 in gingival tissues, GCF and PICF of periodontitis patients and peri-implantitis.

High mobility group chromosomal protein B1 (HMGB1) and N2 (HMGN2), two members of High mobility group (HMG) family, play important role in inflammation. The purposes of this study were to investigate the expression of HMGB1 and HMGN2 in periodontistis. The expression of HMGB1 and HMGN2 mRNA in gingival tissues and gingival crevicular fluid (GCF) in chronic periodontitis (CP), generalized aggressive periodontitis (G-AgP) patients and healthy subjects was detected by real-time PCR. The protein level of HMGB1 and HMGN2 in peri-implant crevicular fluid (PICF), peri-implant crevicular fluid of peri-implantitis (PI-PICF) and normal patients was determined by Western blotting. Furthermore, IL-1ß, IL-6, IL-8, TNF-α and HMGB1 levels in GCF, PI-PICF and healthy -PICF samples from different groups were determined by ELISA. HMGN2 expression was increased in inflamed gingival tissues and GCF from CP and G-ApG groups compared to control group. HMGB1 expression was the highest in the gingival tissues and GCF from CP patients and was accompanied by increased concentrations of IL-1ß, IL-6, IL-8 proinflammaory cytokines. To our knowledge, this is the first study reporting that the expression of HMGB1 and HMGN2 was increased in the gingival tissues and GCF in CP and G-AgP and the PICF in PICF. Our data suggest that HMGB1 may be a potential target for the therapy of periodontitis and PI.

Exogenous HMGN2 inhibits the migration and invasion of osteosarcoma cell lines.

BACKGROUND: Osteosarcoma (OS) is among the most prevalent forms of malignant tumors seen in children and teenagers. Early metastasis is a hallmark of OS, and it is therefore important to find new and more effective treatment targets to improve the survival time of patients with the disease. High mobility group N (HMGNs) is a family of proteins that contributes to the development of a number of different tumors. In particular, HMGN2 was found in our earlier study to be an anti-tumor factor and was seen to impede the metastasis of OS when it was overexpressed. This study aims to further investigate the potential of HMGN2 in anti-tumor treatment. METHODS: We overexpressed HMGN2 in 293FT cells via transfection with recombinant lentiviruses and purified HMGN2 protein with flag tags to treat OS cell lines. The cellular location of exogenous HMGN2 was detected by immunocytochemistry, and wound healing and transwell assays were used to study differences in the rates of migration and invasion of cells between each group. RESULTS: We found that exogenous HMGN2 enters OS cells in a concentration-dependent manner and inhibits the migration and invasion of OS cells, and exogenous HMGN2 regulates the expression of matrix metalloproteinase 2 (MMP2) and MMP9 in OS cells. CONCLUSIONS: Our results demonstrated that exogenous HMGN2 plays a role in inhibiting OS metastasis, which could act as a basis for new ideas for future anti-tumor therapy research.

Non-histone nuclear protein HMGN2 differently regulates the urothelium barrier function by altering expression of antimicrobial peptides and tight junction protein genes in UPEC J96-infected bladder epithelial cell monolayer.

The urinary tract is vulnerable to frequent challenges from environmental microflora. Uropathogenic Escherichia coli (UPEC) makes a major contribution to urinary tract infection (UTI). Previous studies have characterized positive roles of non-histone nuclear protein HMGN2 in lung epithelial innate immune response. In the study presented here, we found HMGN2 expression was up-regulated in UPEC J96-infected urothelium. Surprisingly, over-expression of HMGN2 promoted disruption of BECs 5637 cells' intercellular junctions by down-regulating tight junction (TJs) components' expression and physical structure under J96 infection. Further investigation showed that BECs 5637 monolayer, in which HMGN2 was over-expressed, had significantly increased permeability to J96. Our study systemically explored the regulatory roles of HMGN2 in BECs barrier function during UPEC infection and suggested different modulations of intracellular and paracellular routes through which UPEC invades the bladder epithelium.

Nuclear protein HMGN2 attenuates pyocyanin-induced oxidative stress via Nrf2 signaling and inhibits Pseudomonas aeruginosa internalization in A549 cells.

Pyocyanin (PCN, 1-hydroxy-5-methyl-phenazine) is one of the most essential virulence factors of Pseudomonas aeruginosa (PA) to cause various cytotoxic effects in long-term lung infectious diseases, however the early effect of this bacterial toxin during PA infection and subsequent autonomous immune response in host cells have not been fully understood yet. Our results display that early onset of PCN stimulates Pseudomonas aeruginosa PAO1 adhesion and invasion in A549 cells via ROS production. Non-histone nuclear protein HMGN2 is found to be involved in the regulation of PCN-induced oxidative stress by promoting intracellular ROS clearance. Mechanistically, HMGN2 facilitates nuclear translocation of transcription factor Nrf2 upon PCN stimulation and in turn elevates antioxidant gene expression. We also found that actin cytoskeleton dynamics is targeted by ROS, which is to be exploited by PAO1 for host cell internalization. HMGN2 regulates actin skeleton rearrangement in both PCN-dependent and independent manners and specifically attenuates PCN-mediated PAO1 infection via ROS elimination. These results uncover a novel link between nuclear protein HMGN2 and Nrf2-mediated cellular redox circumstance and suggest roles of HMGN2 in autonomous immune response to PA infection.

Antibacterial mechanism of high-mobility group nucleosomal-binding domain 2 on the Gram-negative bacteria Escherichia coli.

OBJECTIVE: To investigate the antibacterial mechanism of high-mobility group nucleosomal-binding domain 2 (HMGN2) on Escherichia coli K12, focusing on the antibacterial and antibiofilm formation effects. Its chemotactic activity on human neutrophils was also investigated. METHODS: Human tissue-derived HMGN2 (tHMGN2) was extracted from fresh uterus fiber cystadenoma and purified by HP1100 reversed-phase high-performance liquid chromatography (RP-HPLC). Recombinant human HMGN2 (rHMGN2) was generated in E. coli DE3 carrying PET-32a-c(+)-HMGN2. Antibacterial activity of HMGN2 was determined using an agarose diffusion assay and minimum inhibitory concentration (MIC) of HMGN2 was determined by the microdilution broth method. Bacterial membrane permeability assay and DNA binding assay were performed. The antibiofilm effect of HMGN2 was investigated using a crystal violet assay and electron microscopy scanning. The activating effect and chemotactic activity of HMGN2 on neutrophils were determined using a nitroblue tetrazolium (NBT) reduction assay and Transwell chamber cell migration assay, respectively. RESULTS: HMGN2 showed a relatively high potency against Gram-negative bacteria E. coli and the MIC of HMGN2 was 16.25 µg/ml. Elevated bacterial membrane permeability was observed in HMGN2-treated E. coli K12. HMGN2 could also bind the bacterial plasmid and genomic DNA in a dose-dependent manner. The antibiofilm effect of HMGN2 on E. coli K12 was confirmed by crystal violet staining and scanning electron microscopy. However, the activating effects and chemotactic effects of HMGN2 on human neutrophils were not observed. CONCLUSIONS: As an antimicrobial peptide (AMP), HMGN2 possessed a good capacity for antibacterial and antibiofilm activities on E. coli K12. This capacity might be associated with disruption of the bacterial membrane and combination of DNA, which might affect the growth and viability of E. coli.

Surface localization of high-mobility group nucleosome-binding protein 2 on leukemic B cells from patients with chronic lymphocytic leukemia is related to secondary autoimmune hemolytic anemia.

Chronic lymphocytic leukemia (CLL) is the main cause of autoimmune hemolytic anemia (AHA). However, the cellular basis underlying this strong association remains unclear. We previously demonstrated that leukemic B cells from patients with CLL recognize the erythrocyte protein Band 3, a prevalent autoantigen in AHA. Here we show that the major binding site of Band 3 on leukemic cells is an extrinsic protein identified as high-mobility group nucleosome binding protein 2 (HMGN2), a nucleosome-interacting factor which has not been previously reported at the cell surface. T lymphocytes do not express HMGN2 or bind Band 3. Removal of HMGN2 from the cell membrane abrogated the capacity of Band 3-pulsed CLL cells to induce CD4 + T cell proliferation. We conclude that surface HMGN2 in leukemic B cells is involved in Band 3 binding, uptake and presentation to CD4 + T lymphocytes, and as such may favor the initiation of AHA secondary to CLL.

Nucleosome-binding protein HMGN2 exhibits antitumor activity in oral squamous cell carcinoma.

Natural killer (NK) cells and cytolytic T lymphocytes (CTLs) serve as effectors in the antitumor response. High mobility group nucleosomal binding domain 2 (HMGN2) is a candidate effector molecule involved in CTL and NK cell function. In the current study, recombinant human HMGN2 was isolated and purified from transformed Escherichia coli. Tca8113 cells, an oral squamous cell carcinoma line, were treated with a variety of HMGN2 protein concentrations and cell growth was analyzed. HMGN2 significantly inhibited the growth of Tca8113 cells and was predicted to arrest cells in the S phase. Moreover, HMGN2 treatment increased the apoptosis rate of Tca8113 cells. Western blotting indicated the upregulation of p53 and Bax proteins, whereas Bcl-2 was significantly downregulated. In addition, caspase-3 was found to be activated. Furthermore, the HMGN2 protein may suppress the growth of Tca8113 cells in vivo. The results of the current study indicated that the HMGN2 protein may inhibit the growth of oral squamous cell carcinoma and HMGN2 may represent an antitumor effector molecule of CTL or NK cells.

Human colonic mucus is a reservoir for antimicrobial peptides.

BACKGROUND AND AIMS: To prevent bacterial adherence and translocation, the colonic mucosa is covered by a protecting mucus layer and the epithelium synthesizes antimicrobial peptides. The present qualitative study investigated the contents and interaction of these peptides in and with rectal mucus. METHODS: Rectal mucus extracts were analyzed for antimicrobial activity and screened with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Dot blot and immunohistochemistry for antimicrobial peptides. In addition, binding of AMPs to mucins was investigated by Western blot and enzyme-linked lectin assays. RESULTS: In functional tests the mucus layer exhibited a strong antimicrobial activity. We detected 11 antimicrobial peptides in mucus extracts from healthy persons including the defensins HBD-1 and -3, the cathelicidin LL-37, ubiquitin, lysozyme, histones, high mobility group nucleosome-binding domain-containing protein 2, ubiquicidin and other ribosomal proteins. AMPs were bound by mucins but this was demonstrated to be reversible and inhibition of antibacterial activity was limited. CONCLUSION: These findings indicate that epithelial antimicrobial peptides are retained in the intestinal mucus layer without losing their efficacy. Thus, the mucus layer and its composition provide an attractive drug target to restore antimicrobial barrier function in intestinal diseases.