HMG chromosomal proteins in development and disease

LINC00460/DHX9/IGF2BP2 complex promotes colorectal cancer proliferation and metastasis by mediating HMGA1 mRNA stability depending on m6A modification

Background

Increasing studies have shown that long noncoding RNAs (lncRNAs) are pivotal regulators participating in carcinogenic progression and tumor metastasis in colorectal cancer (CRC). Although lncRNA long intergenic noncoding RNA 460 (LINC00460) has been reported in CRC, the role and molecular mechanism of LINC00460 in CRC progression still requires exploration.

Methods

The expression levels of LINC00460 were analyzed by using a tissue microarray containing 498 CRC tissues and their corresponding non-tumor adjacent tissues. The correlations between the LINC00460 expression level and clinicopathological features were evaluated. The functional characterization of the role and molecular mechanism of LINC00460 in CRC was investigated through a series of in vitro and in vivo experiments.

Results

LINC00460 expression was increased in human CRC, and high LINC00460 expression was correlated with poor five-year overall survival and disease-free survival. LINC00460 overexpression sufficiently induced the epithelial–mesenchymal transition and promoted tumor cell proliferation, migration, and invasion in vitro and tumor growth and metastasis in vivo. In addition, LINC00460 enhanced the protein expression of high-mobility group AT-hook 1 (HMGA1) by directly interacting with IGF2BP2 and DHX9 to bind the 3′ untranslated region (UTR) of HMGA1 mRNA and increased the stability of HMGA1 mRNA. In addition, the N6-methyladenosine (m6A) modification of HMGA1 mRNA by METTL3 enhanced HMGA1 expression in CRC. Finally, it suggested that HMGA1 was essential for LINC00460-induced cell proliferation, migration, and invasion.

Conclusions

LINC00460 may be a novel oncogene of CRC through interacting with IGF2BP2 and DHX9 and bind to the m6A modified HMGA1 mRNA to enhance the HMGA1 mRNA stability. LINC00460 can serve as a promising predictive biomarker for the diagnosis and prognosis among patients with CRC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01857-2.

Cardiomyocyte-restricted high-mobility group box 1 (HMGB1) deletion leads to small heart and glycolipid metabolic disorder through GR/PGC-1α signalling

Cardiac growth and remodelling are key biological processes influencing the physiological performance of the heart, and a previous study showed a critical role for intracellular HMGB1 in vitro. However, the in vivo study, which used conditional Hmgb1 ablation, did not show a significant effect on cellular or organic function. We have demonstrated the extracellular effect of HMGB1 as a pro-inflammatory molecule on cardiac remodelling. In this study, we found that HMGB1 deletion by cTnT-Cre in mouse hearts altered glucocorticoid receptor (GR) function and glycolipid metabolism, eventually leading to growth retardation, small heart and heart failure. The subcellular morphology did not show a significant change caused by HMGB1 knockout. The heart showed significant elevation of glycolysis, free fatty acid deposition and related enzyme changes. Transcriptomic analysis revealed a list of differentially expressed genes that coincide with glucocorticoid receptor function in neonatal mice and a significant increase in inflammatory genes in adult mice. Cardiac HMGB1 knockout led to a series of changes in PGC-1α, UCP3 and GyK, which were the cause of metabolic changes and further impacted cardiac function. Ckmm-Cre Hmgb1^fl/fl mice did not show a specific phenotype, which was consistent with the reported negative result of cardiomyocyte-specific Hmgb1 deletion via MHC-Cre. We concluded that HMGB1 plays essential roles in maintaining normal cardiac growth, and different phenotype from cardiac-specific HMGB1-deficient mice may be caused by the cross with mice of different Cre strains.

Role of RIN1 on telomerase activity driven by EGF-Ras mediated signaling in breast cancer

Epidermal growth factor (EGF)-receptor regulates several downstream signaling pathways upon EGF stimulation that involves cell proliferation, migration and invasion. Internalized EGF-receptor is either recycled or degraded, which fate is regulated in part by Ras interference 1 (RIN1). In this study, we tested the hypothesis that RIN1, a Ras effector protein and Rab5 guanine nucleotide exchange factor, controls several signaling molecules leading to the modulation of the telomerase activity; thus, allowing proper cell proliferation. We report that expression of RIN1 completely blocked proliferation of MCF-12 A and MCF-7 cells, while partially inhibited proliferation of MDA-MB-231 cells upon EGF stimulation. Furthermore, expression of the C-terminal region of RIN1 selectively plays a critical role in the inhibition of the proliferation of MDA-MB-231 cells. However, this inhibitory effect was specifically affected by the independent expression of RIN1:Vsp9 and RIN1:RA domains. Additionally, endogenous level of expression of RIN1 was decreased in metastatic MDA-MB-231 cells as compared with non-tumorigenic MCF-12 A cells. We observed that expression of RIN1:R94A mutant blocked the proliferation of MDA-MB-231 cells, while expression of RIN1:Y561F and RIN1:R629A mutants completely reversed the inhibitory effect of RIN1:WT. Consistent with our observations, we found that expression of RIN1:WT in MDA-MB-231 cells diminished both protein kinase B (AKT) and extracellular-signal-regulated kinase 1/2 (ERK1/2) activities while p38 mitogen-activated protein kinases (p38 MAPK) and stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK) were unaffected, but it produced downregulation of cellular-myelocytomatosis (c-Myc), erythroblast transformation specific (Ets2) and signal transducer and activator of transcription 3 (Stat3) activities. Inversely, expression of high-mobility group box 1 (HMBG1) was inhibited whereas expression of forkhead box transcription factor 1 (FOXO1) was increased in cells expressing RIN1. Interestingly, expression of RIN1 blocked telomerase activity and human telomerase reverse transcriptase (hTERT) expression, which correlated with the downregulations of c-Myc, Ets-2 and Stat3 activation. Taken together these findings indicate that RIN1 is a critical player in the modulation of the telomerase activity as well as hTERT expression in MDA-MB-231 cells upon EGF stimulation.

Free light chains injure proximal tubule cells through the STAT1/HMGB1/TLR axis

Free light chains (FLCs) induce inflammatory pathways in proximal tubule cells (PTCs). The role of TLRs in these responses is unknown. Here we present findings on the role of TLRs in FLC-induced PTC injury. We exposed human kidney PTC cultures to κ and λ FLCs and used cell supernatants and pellets for ELISA and gene expression studies. We also analyzed tissues from Stat1-/- and littermate control mice treated with daily i.p. injections of a κ FLC for 10 days. FLCs increased the expression of TLR2, TLR4, and TLR6 via HMGB1, a damage-associated molecular pattern. Countering TLR2, TLR4, and TLR6 through GIT-27 or specific TLR siRNAs reduced downstream cytokine responses. Blocking HMGB1 through siRNA or pharmacologic inhibition, or via STAT1 inhibition, reduced FLC-induced TLR2, TLR4, and TLR6 expression. Blocking endocytosis of FLCs through silencing of megalin/cubilin, with bafilomycin A1 or hypertonic sucrose, attenuated FLC-induced cytokine responses in PTCs. IHC showed decreased TLR4 and TLR6 expression in kidney sections from Stat1-/- mice compared with their littermate controls. PTCs exposed to FLCs released HMGB1, which induced expression of TLR2, TLR4, and TLR6 and downstream inflammation. Blocking FLCs' endocytosis, Stat1 knockdown, HMGB1 inhibition, and TLR knockdown each rescued PTCs from FLC-induced injury.

Regulation of Neurogenesis in Mouse Brain by HMGB1

The High Mobility Group Box 1 (HMGB1) is the most abundant nuclear nonhistone protein that is involved in transcription regulation. In addition, HMGB1 has previously been found as an extracellularly acting protein enhancing neurite outgrowth in cultured neurons. Although HMGB1 is widely expressed in the developing central nervous system of vertebrates and invertebrates, its function in the developing mouse brain is poorly understood. Here, we have analyzed developmental defects of the HMGB1 null mouse forebrain, and further examined our findings in ex vivo brain cell cultures. We find that HMGB1 is required for the proliferation and differentiation of neuronal stem cells/progenitor cells. Enhanced apoptosis is also found in the neuronal cells lacking HMGB1. Moreover, HMGB1 depletion disrupts Wnt/β-catenin signaling and the expression of transcription factors in the developing cortex, including Foxg1, Tbr2, Emx2, and Lhx6. Finally, HMGB1 null mice display aberrant expression of CXCL12/CXCR4 and reduced RAGE signaling. In conclusion, HMGB1 plays a critical role in mammalian neurogenesis and brain development.

Midbrain Dopaminergic Neuron Development at the Single Cell Level: In vivo and in Stem Cells

Parkinson's disease (PD) is a progressive neurodegenerative disorder that predominantly affects dopaminergic (DA) neurons of the substantia nigra. Current treatment options for PD are symptomatic and typically involve the replacement of DA neurotransmission by DA drugs, which relieve the patients of some of their motor symptoms. However, by the time of diagnosis, patients have already lost about 70% of their substantia nigra DA neurons and these drugs offer only temporary relief. Therefore, cell replacement therapy has garnered much interest as a potential treatment option for PD. Early studies using human fetal tissue for transplantation in PD patients provided proof of principle for cell replacement therapy, but they also highlighted the ethical and practical difficulties associated with using human fetal tissue as a cell source. In recent years, advancements in stem cell research have made human pluripotent stem cells (hPSCs) an attractive source of material for cell replacement therapy. Studies on how DA neurons are specified and differentiated in the developing mouse midbrain have allowed us to recapitulate many of the positional and temporal cues needed to generate DA neurons in vitro. However, little is known about the developmental programs that govern human DA neuron development. With the advent of single-cell RNA sequencing (scRNA-seq) and bioinformatics, it has become possible to analyze precious human samples with unprecedented detail and extract valuable high-quality information from large data sets. This technology has allowed the systematic classification of cell types present in the human developing midbrain along with their gene expression patterns. By studying human development in such an unbiased manner, we can begin to elucidate human DA neuron development and determine how much it differs from our knowledge of the rodent brain. Importantly, this molecular description of the function of human cells has become and will increasingly be a reference to define, evaluate, and engineer cell types for PD cell replacement therapy and disease modeling.

HMGA1 Regulates the Stem Cell-Like Properties of Circulating Tumor Cells from GIST Patients via Wnt/β-Catenin Pathway

Background

Gastrointestinal stromal tumor (GIST) is the most common sarcoma of the digestive system. Circulating tumor cells (CTCs) have been proven to be critical in the recurrence and metastasis of diseases; however, the characteristics of CTCs of GIST are still unclear.

Methods

We sorted out and verified the validity of CTCs from peripheral blood of gastrointestinal stromal tumor (GIST) patients with or without heterochronous liver metastasis using flow cytometry (FCM). Differential genes were analyzed between the GIST patients with and without liver metastasis using next-generation sequencing (NGS).

Results

The preliminary study on the characteristics of CTCs revealed that CTCs of GIST patients with heterochronous liver metastasis had stronger stem cell-like properties (SC-like properties) than CTCs of those without liver metastasis. Furthermore, NGS followed with a series of assays revealed that HMGA1 played a critical role in regulating the SC-like properties of CTCs. Mechanistically, HMGA1 could activate Wnt/β-catenin pathway in vitro and vivo. Moreover, we found that the expression level of HMGA1 in CTCs was an independent risk factor probably influencing the prognosis of GIST patients.

Conclusion

Our findings indicate the significant role of HMGA1 in SC-like properties, IM resistance and eventually hepatic metastasis formation of CTCs. Targeting HMGA1 in CTCs may be a therapeutic strategy for GIST patients with hepatic metastasis.

HMGA and Cancer: A Review on Patent Literatures

BACKGROUND

The high mobility group A proteins modulate the transcription of numerous genes by interacting with transcription factors and/or altering the structure of chromatin. These proteins are involved in both benign and malignant neoplasias as a result of several pathways. A large amount of benign human mesenchymal tumors has rearrangements of HMGA genes. On the contrary, malignant tumors show unarranged HMGA overexpression that is frequently and causally related to neoplastic cell transformation. Here, we review the function of the HMGA proteins in human neoplastic disorders, the pathways by which they contribute to carcinogenesis and the new patents focused on targeting HMGA proteins.

OBJECTIVE

Current review was conducted to check the involvement of HMGA as a druggable target in cancer treatment.

METHODS

We reviewed the most recent patents focused on targeting HMGA in cancer treatment analyzing patent literature published during the last years, including the World Intellectual Property Organization (WIPO®), United States Patent Trademark Office (USPTO®), Espacenet®, and Google Patents.

RESULTS

HMGA proteins are intriguing targets for cancer therapy and are objects of different patents based on the use of DNA aptamers, inhibitors, oncolytic viruses, antisense molecules able to block their oncogenic functions.

CONCLUSION

Powerful strategies able to selectively interfere with HMGA expression and function could represent a helpful approach in the development of new anti-cancer therapies.

Mir-370-3p Impairs Glioblastoma Stem-Like Cell Malignancy Regulating a Complex Interplay between HMGA2/HIF1A and the Oncogenic Long Non-Coding RNA (lncRNA) NEAT1

Glioblastoma (GBM) is the most aggressive and prevalent form of a human brain tumor in adults. Several data have demonstrated the implication of microRNAs (miRNAs) in tumorigenicity of GBM stem-like cells (GSCs). The regulatory functions of miRNAs in GSCs have emerged as potential therapeutic candidates for glioma treatment. The current study aimed at investigating the function of miR-370-3p in glioma progression, as aberrant expression of miR-370-3p, is involved in various human cancers, including glioma. Analyzing our collection of GBM samples and patient-derived GSC lines, we found the expression of miR-370-3p significantly downregulated compared to normal brain tissues and normal neural stem cells. Restoration of miR-370-3p expression in GSCs significantly decreased proliferation, migration, and clonogenic abilities of GSCs, in vitro, and tumor growth in vivo. Gene expression analysis performed on miR-370-3p transduced GSCs, identified several transcripts involved in Epithelial to Mesenchymal Transition (EMT), and Hypoxia signaling pathways. Among the genes downregulated by the restored expression of miR-370-3p, we found the EMT-inducer high-mobility group AT-hook 2 (HMGA2), the master transcriptional regulator of the adaptive response to hypoxia, Hypoxia-inducible factor (HIF)1A, and the long non-coding RNAs (lncRNAs) Nuclear Enriched Abundant Transcript (NEAT)1. NEAT1 acts as an oncogene in a series of human cancers including gliomas, where it is regulated by the Epidermal Growth Factor Receptor (EGFR) pathways, and contributes to tumor growth and invasion. Noteworthy, the expression levels of miR-370-3p and NEAT1 were inversely related in both GBM tumor specimens and GSCs, and a dual-luciferase reporter assay proved the direct binding between miR-370-3p and the lncRNAs NEAT1. Our results identify a critical role of miR-370-3p in the regulation of GBM development, indicating that miR-370-3p acts as a tumor-suppressor factor inhibiting glioma cell growth, migration and invasion by targeting the lncRNAs NEAT1, HMGA2, and HIF1A, thus, providing a potential candidate for GBM patient treatment.

Prevention of Chromatin Destabilization by FACT Is Crucial for Malignant Transformation

Histone chaperone FACT is commonly expressed and essential for the viability of transformed but not normal cells, and its expression levels correlate with poor prognosis in patients with cancer. FACT binds several components of nucleosomes and has been viewed as a factor destabilizing nucleosomes to facilitate RNA polymerase passage. To connect FACT's role in transcription with the viability of tumor cells, we analyzed genome-wide FACT binding to chromatin in conjunction with transcription in mouse and human cells with different degrees of FACT dependence. Genomic distribution and density of FACT correlated with the intensity of transcription. However, FACT knockout or knockdown was unexpectedly accompanied by the elevation, rather than suppression, of transcription and with the destabilization of chromatin in transformed, but not normal cells. These data suggest that FACT stabilizes and reassembles nucleosomes disturbed by transcription. This function is vital for tumor cells because malignant transformation is accompanied by chromatin destabilization.

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FACT is essential for viability of the tumor, but not for normal cells

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FACT level depends on transcription, but transcription does not depend on FACT

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FACT preserves nucleosomes during transcription to maintain chromatin integrity

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FACT maintains chromatin in destabilized state during malignant transformation

Epigenetic regulation for acquiring glial identity by neural stem cells during cortical development

The nervous system consists of several hundred neuronal subtypes and glial cells that show specific gene expression and are generated from common ancestors, neural stem cells (NSCs). As the experimental techniques and molecular tools to analyze epigenetics and chromatin structures are rapidly advancing, the comprehensive events and genome-wide states of DNA methylation, histone modifications, and chromatin accessibility in developing NSCs are gradually being unveiled. Here, we review recent advances in elucidating the role of epigenetic and chromatin regulation in NSCs, especially focusing on the acquisition of glial identity and how epigenetic regulation enables the temporal regulation of NSCs during murine cortical development.

Nucleus-specific linker histones Hho1 and Mlh1 form distinct protein interactions during growth, starvation and development in Tetrahymena thermophila

Chromatin organization influences most aspects of gene expression regulation. The linker histone H1, along with the core histones, is a key component of eukaryotic chromatin. Despite its critical roles in chromatin structure and function and gene regulation, studies regarding the H1 protein-protein interaction networks, particularly outside of Opisthokonts, are limited. The nuclear dimorphic ciliate protozoan Tetrahymena thermophila encodes two distinct nucleus-specific linker histones, macronuclear Hho1 and micronuclear Mlh1. We used a comparative proteomics approach to identify the Hho1 and Mlh1 protein-protein interaction networks in Tetrahymena during growth, starvation, and sexual development. Affinity purification followed by mass spectrometry analysis of the Hho1 and Mlh1 proteins revealed a non-overlapping set of co-purifying proteins suggesting that Tetrahymena nucleus-specific linker histones are subject to distinct regulatory pathways. Furthermore, we found that linker histones interact with distinct proteins under the different stages of the Tetrahymena life cycle. Hho1 and Mlh1 co-purified with several Tetrahymena-specific as well as conserved interacting partners involved in chromatin structure and function and other important cellular pathways. Our results suggest that nucleus-specific linker histones might be subject to nucleus-specific regulatory pathways and are dynamically regulated under different stages of the Tetrahymena life cycle.

Biological Functions of HMGN Chromosomal Proteins

Chromatin plays a key role in regulating gene expression programs necessary for the orderly progress of development and for preventing changes in cell identity that can lead to disease. The high mobility group N (HMGN) is a family of nucleosome binding proteins that preferentially binds to chromatin regulatory sites including enhancers and promoters. HMGN proteins are ubiquitously expressed in all vertebrate cells potentially affecting chromatin function and epigenetic regulation in multiple cell types. Here, we review studies aimed at elucidating the biological function of HMGN proteins, focusing on their possible role in vertebrate development and the etiology of disease. The data indicate that changes in HMGN levels lead to cell type-specific phenotypes, suggesting that HMGN optimize epigenetic processes necessary for maintaining cell identity and for proper execution of specific cellular functions. This manuscript contains tables that can be used as a comprehensive resource for all the English written manuscripts describing research aimed at elucidating the biological function of the HMGN protein family.

Characterization of Full-Length Transcriptome Sequences and Splice Variants of Lateolabrax maculatus by Single-Molecule Long-Read Sequencing and Their Involvement in Salinity Regulation

Transcriptome complexity plays crucial roles in regulating the biological functions of eukaryotes. Except for functional genes, alternative splicing and fusion transcripts produce a vast expansion of transcriptome diversity. In this study, we applied PacBio single-molecule long-read sequencing technology to unveil the whole transcriptome landscape of Lateolabrax maculatus. We obtained 28,809 high-quality non-redundant transcripts, including 18,280 novel isoforms covering 8,961 annotated gene loci within the current reference genome and 3,172 novel isoforms. A total of 10,249 AS events were detected, and intron retention was the predominant AS event. In addition, 1,359 alternative polyadenylation events, 3,112 lncRNAs, 29,609 SSRs, 365 fusion transcripts, and 1,194 transcription factors were identified in this study. Furthermore, we performed RNA-Seq analysis combined with Iso-Seq results to investigate salinity regulation mechanism at the transcripts level. A total of 518 transcripts were differentially expressed, which were further divided into 8 functional groups. Notably, transcripts from the same genes exhibited similar or opposite expression patterns. Our study provides a comprehensive view of the transcriptome complexity in L. maculatus, which significantly improves current gene models. Moreover, the diversity of the expression patterns of transcripts may enhance the understanding of salinity regulatory mechanism in L. maculatus and other euryhaline teleosts.

Uterine deficiency of high-mobility group box-1 (HMGB1) protein causes implantation defects and adverse pregnancy outcomes

A reciprocal communication between the implantation-competent blastocyst and the receptive uterus is essential to successful implantation and pregnancy success. Progesterone (P₄) signaling via nuclear progesterone receptor (PR) is absolutely critical for pregnancy initiation and its success in most eutherian mammals. Here we show that a nuclear protein high-mobility group box-1 (HMGB1) plays a critical role in implantation in mice by preserving P₄-PR signaling. Conditional deletion of uterine Hmgb1 by a Pgr-Cre driver shows implantation defects accompanied by decreased stromal cell Hoxa10 expression and cell proliferation, two known signatures of inefficient responsiveness of stromal cells to PR signaling in implantation. These mice evoke inflammatory conditions with sustained macrophage accumulation in the stromal compartment on day 4 of pregnancy with elevated levels of macrophage attractants Csf1 and Ccl2. The results are consistent with the failure of exogenous P₄ administration to rescue implantation deficiency in the mutant females. These early defects are propagated throughout the course of pregnancy and ultimately result in substantial subfertility. Collectively, the present study provides evidence that nuclear HMGB1 contributes to successful blastocyst implantation by sustaining P₄-PR signaling and restricting macrophage accumulation to attenuate harmful inflammatory responses.

Photoswitchable peptides for spatiotemporal control of biological functions

Light is unsurpassed in its ability to modulate biological interactions. Since their discovery, chemists have been fascinated by photosensitive molecules capable of switching between isomeric forms, known as photoswitches. Photoswitchable peptides have been recognized for many years; however, their functional implementation in biological systems has only recently been achieved. Peptides are now acknowledged as excellent protein-protein interaction modulators and have been important in the emergence of photopharmacology. In this review, we briefly explain the different classes of photoswitches and summarize structural studies when they are incorporated into peptides. Importantly, we provide a detailed overview of the rapidly increasing number of examples, where biological modulation is driven by the structural changes. Furthermore, we discuss some of the remaining challenges faced in this field. These exciting proof-of-principle studies highlight the tremendous potential of photocontrollable peptides as optochemical tools for chemical biology and biomedicine.

Effect of Doxorubicin on Squamous Cell Carcinoma of Skin: Assessment by MRI Relaxometry at 4.7T

Squamous cell carcinoma (SCC) of skin has no standard treatment regimen, resulting in recurrences/metastasis. Although, doxorubicin (Dox), an anthracycline antibiotic has demonstrated some degree of efficacy. Molecular imaging can help in assessment of treatment response and prognosis of SCCs. MRI data showed that spin-spin relaxation (T2) time was longer (138 ± 2 msec) in Dox treated Test-II and there is no significant difference in spin-lattice relaxation (T1) time with respective controls. These findings further corroborated with the histology, proliferation index, apoptotic index, and HMGA1 protein expression. Thus, MRI may be a useful tool for monitoring treatment response noninvasively for skin tumor prognosis.

SOXopathies: Growing Family of Developmental Disorders Due to SOX Mutations

The SRY-related (SOX) transcription factor family pivotally contributes to determining cell fate and identity in many lineages. Since the original discovery that SRY deletions cause sex reversal, mutations in half of the 20 human SOX genes have been associated with rare congenital disorders, henceforward called SOXopathies. Mutations are generally de novo, heterozygous, and inactivating, revealing gene haploinsufficiency, but other types, including duplications, have been reported too. Missense variants primarily target the HMG domain, the SOX hallmark that mediates DNA binding and bending, nuclear trafficking, and protein-protein interactions. We here review key clinical and molecular features of SOXopathies and discuss the prospect that the disease family likely involves more SOX genes and larger clinical and genetic spectrums than currently appreciated.

High-mobility group box 2 promoted proliferation of cervical cancer cells by activating AKT signaling pathway

Cervical cancer is one of the leading killers for female worldwide. Nevertheless, the less knowledge of molecular mechanism for cervical cancer limited the improvement of treatment effects. High-mobility group box 2 (HMGB2) belongs to the HMGB family, which could play diverse roles in cell proliferation. This work mainly aimed to study the functions of HMGB2 on cervical cancer cells proliferation. HMGB2 was highly expressed in cervical cancer tissue. The results of real-time polymerase chain reaction and Western blot analysis showed that HMGB2 was expressed in all the five cervical cancer cells (HeLa, CaSki, SiHa, C-33A, and C4-1 cells). In addition, HMGB2 overexpression obviously improved cell viability and promoted cell cycle progression, which suggested that HMGB2 could promote proliferation of cervical cancer cells. Moreover, HMGB2 overexpression increased the level of p-AKT and reduced the levels of p21 and p27. However, HMGB2 downregulation had contrary influences on cell proliferation, cell cycle distribution and the levels of p-AKT, p21, and p27. Notably, LY294002, as an inhibitor of AKT signaling pathway, could significantly weaken the effects of HMGB2 overexpression, which indicated that HMGB2 might promote cell proliferation by activating AKT signaling pathway. Therefore, HMGB2 was hopeful to be a candidate as a new biomarker and therapy target for cervical cancer.

Growth Factor Independence 1B-Mediated Transcriptional Repression and Lineage Allocation Require Lysine-Specific Demethylase 1-Dependent Recruitment of the BHC Complex

Growth factor independence 1B (GFI1B) coordinates assembly of transcriptional repressor complexes comprised of corepressors and histone-modifying enzymes to control gene expression programs governing lineage allocation in hematopoiesis. Enforced expression of GFI1B in K562 erythroleukemia cells favors erythroid over megakaryocytic differentiation, providing a platform to define molecular determinants of binary fate decisions triggered by GFI1B. We deployed proteome-wide proximity labeling to identify factors whose inclusion in GFI1B complexes depends upon GFI1B's obligate effector, lysine-specific demethylase 1 (LSD1). We show that GFI1B preferentially recruits core and putative elements of the BRAF-histone deacetylase (HDAC) (BHC) chromatin-remodeling complex (LSD1, RCOR1, HMG20A, HMG20B, HDAC1, HDAC2, PHF21A, GSE1, ZMYM2, and ZNF217) in an LSD1-dependent manner to control acquisition of erythroid traits by K562 cells. Among these elements, depletion of both HMG20A and HMG20B or of GSE1 blocks GFI1B-mediated erythroid differentiation, phenocopying impaired differentiation brought on by LSD1 depletion or disruption of GFI1B-LSD1 binding. These findings demonstrate the central role of the GFI1B-LSD1 interaction as a determinant of BHC complex recruitment to enable cell fate decisions driven by GFI1B.

Ion counting demonstrates a high electrostatic field generated by the nucleosome

In eukaryotes, a first step towards the nuclear DNA compaction process is the formation of a nucleosome, which is comprised of negatively charged DNA wrapped around a positively charged histone protein octamer. Often, it is assumed that the complexation of the DNA into the nucleosome completely attenuates the DNA charge and hence the electrostatic field generated by the molecule. In contrast, theoretical and computational studies suggest that the nucleosome retains a strong, negative electrostatic field. Despite their fundamental implications for chromatin organization and function, these opposing views of nucleosome electrostatics have not been experimentally tested. Herein, we directly measure nucleosome electrostatics and find that while nucleosome formation reduces the complex charge by half, the nucleosome nevertheless maintains a strong negative electrostatic field. Our studies highlight the importance of considering the polyelectrolyte nature of the nucleosome and its impact on processes ranging from factor binding to DNA compaction.

CXCL12-regulated miR-370-3p functions as a tumor suppressor gene by targeting HMGA2 in nonfunctional pituitary adenomas

Silencing of noncoding genes within the imprinted DLK1-MEG3 locus is exclusive to human nonfunctional pituitary adenomas (NFPAs), but the exact mechanism is still unclear. This study was designed to demonstrate the impact of CXCL12 on the expression of miRNAs within this locus and phenotypic alterations of NFPAs. Human NFPA samples were collected for screening differentially expressed miRNAs by CXCL12. Target mRNAs of the miRNAs were predicted and verified in vitro. Tumor phenotypic alterations were also tested. Another 51 NFPA samples were enrolled to examine the correlation and clinical features. The expression of miR-370 was decreased by CXCL12 treatment in NFPAs. miR-370-3p was predicted and verified to target HMGA2 as a tumor suppressor gene. Overexpression of HMGA2 inhibited its antitumor function. miR-370-3p was downregulated and HMGA2 was upregulated significantly in High grade NFPAs. In conclusion, the CXCL12/miR-370-3p/HMGA2 signaling pathway is involved in tumor growth and invasiveness of NFPAs.

KMT1 family methyltransferases regulate heterochromatin-nuclear periphery tethering via histone and non-histone protein methylation

Euchromatic histone methyltransferases (EHMTs), members of the KMT1 family, methylate histone and non-histone proteins. Here, we uncover a novel role for EHMTs in regulating heterochromatin anchorage to the nuclear periphery (NP) via non-histone methylation. We show that EHMTs methylate and stabilize LaminB1 (LMNB1), which associates with the H3K9me2-marked peripheral heterochromatin. Loss of LMNB1 methylation or EHMTs abrogates heterochromatin anchorage at the NP We further demonstrate that the loss of EHMTs induces many hallmarks of aging including global reduction of H3K27methyl marks and altered nuclear morphology. Consistent with this, we observe a gradual depletion of EHMTs, which correlates with loss of methylated LMNB1 and peripheral heterochromatin in aging human fibroblasts. Restoration of EHMT expression reverts peripheral heterochromatin defects in aged cells. Collectively, our work elucidates a new mechanism by which EHMTs regulate heterochromatin domain organization and reveals their impact on fundamental changes associated with the intrinsic aging process.

Comparative Study of Photoswitchable Zinc-Finger Domain and AT-Hook Motif for Light-Controlled Peptide-DNA Binding

DNA-peptide interactions are involved in key life processes, including DNA recognition, replication, transcription, repair, organization, and modification. Development of tools that can influence DNA-peptide binding non-invasively with high spatiotemporal precision could aid in determining its role in cells and tissues. Here, the design, synthesis, and study of photocontrolled tools for sequence-specific small peptide-DNA major and minor groove interactions are reported, shedding light on DNA binding by transcriptionally active peptides. In particular, photoswitchable moieties were implemented in the peptide backbone or turn region. In each case, DNA binding was affected by photochemical isomerization, as determined in fluorescent displacement assays on model DNA strands, which provides promising tools for DNA modulation.

The expressions of HMGA2 and Thy1 in extrahepatic cholangiocarcinoma and their clinicopathological significances

AIMS

Extrahepatic cholangiocarcinoma is a malignant tumor and poor prognosis with intrinsic resistance to cytotoxic agents. The molecular mechanism associated with high malignancy and resistance to chemotherapy and radiotherapy has not been fully elucidated. This study aims to investigate the clinicopathological significances of HMGA2 and Thy1 expression in extrahepatic cholangiocarcinoma.

METHODS

The expressions of HMGA2 and Thy1 in 100 extrahepatic cholangiocarcinoma, 30 peritumoral tissues, 10 adenoma and 15 normal biliary tract tissues were assayed using EnVision immunohistochemistry.

RESULTS

The HMGA2 and Thy1 proteins were overexpression in extrahepatic cholangiocarcinoma compared to peritumoral tissues, adenoma, and normal biliary tract tissues (P < 0.05 or P < 0.01). Adenoma and pericancerous tissues with positive HMGA2 or/and Thy1 protein expression exhibited atypical hyperplasia. The positive correlation was found between the expression of HMGA2 and Thy1 in extrahepatic cholangiocarcinoma (P < 0.01). The positive rates of HMGA2 and Thy1 expression were significantly higher in cases with poor differentiation, lymph node metastasis, invasion, and TNM stage III or IV and no resection (biopsy only) (P < 0.05 or P < 0.01). Kaplan-Meier survival analysis showed that the survival of extrahepatic cholangiocarcinoma patients with positive HMGA2 and/or Thy1 expression is significantly shorter than patients with negative HMGA2 and/or Thy1 expression (P = 0.000). Cox multivariate analysis revealed that positive HMGA2 and/or Thy1 expressions were independently poor prognosis factors in extrahepatic cholangiocarcinoma patients. We calculated the AUC for HMGA2 (AUC = 0.610, 95%CI: 0.519-0.702), or Thy1 (AUC = 0.675, 95%CI: 0.588-0.762), respectively.

CONCLUSIONS

The present study indicated that positive HMGA2 and Thy1 expression are closely associated with the pathogenesis, clinical, pathological and biological behaviors, and poor prognosis in patients with extrahepatic cholangiocarcinoma.

Chromatin Stability as a Target for Cancer Treatment

In this essay, I propose that DNA-binding anti-cancer drugs work more via chromatin disruption than DNA damage. Success of long-awaited drugs targeting cancer-specific drivers is limited by the heterogeneity of tumors. Therefore, chemotherapy acting via universal targets (e.g., DNA) is still the mainstream treatment for cancer. Nevertheless, the problem with targeting DNA is insufficient efficacy due to high toxicity. I propose that this problem stems from the presumption that DNA damage is critical for the anti-cancer activity of these drugs. DNA in cells exists as chromatin, and many DNA-targeting drugs alter chromatin structure by destabilizing nucleosomes and inducing histone eviction from chromatin. This effect has been largely ignored because DNA damage is seen as the major reason for anti-cancer activity. I discuss how DNA-binding molecules destabilize chromatin, why this effect is more toxic to tumoral than normal cells, and why cells die as a result of chromatin destabilization.

HMGB2 promotes the malignancy of human gastric cancer and indicates poor survival outcome

HMGB2 is an important protein in carcinogenesis. However, little is known about the specific role of HMGB2 in gastric cancer. In the present study, HMGB2 expression was evaluated in 198 primary gastric cancer tissues and their adjacent nontumor controls. The correlation between HMGB2 expression and clinico-pathological features and survival was assessed. The effect of HMGB2 on cell proliferation, invasion, and glycolysis was examined in vitro. The expression of HMGB2 was significantly increased in human gastric cancer when compared with nontumor tissues (P < .001). High HMGB2 expression correlated with large tumor size (P = .001), advanced T stage (P = .007), and presence of lymph node metastasis (P = .004). Moreover, high HMGB2 expression was validated as an independent prognostic factor in both univariate and multivariate analyses (P < .05). Experimentally, silencing HMGB2 expression by stable transfected shRNA significantly decreased the proliferation, invasion, and glycolysis of gastric cancer cells. In conclusion, HMGB2 is a novel prognostic biomarker for survival in gastric cancer, and knockdown HMGB2 expression in gastric cancer cells attenuated proliferation and invasion, and impaired glycolysis in gastric cancer cells. Hence, HMGB2 may serve as a new biomarker and a potential therapeutic target in gastric cancer.

Loss of high-mobility group N5 contributes to the promotion of human endometrial stromal cell decidualization

PURPOSE

High-mobility group N (HMGN) proteins are the only non-histone proteins that specifically bind within the nucleosome between core histones and DNA. Among them, HMGN5 is one of the candidates that could participate in mouse endometrial decidualization; however, the specific role of HMGN5 remains to be clarified in human endometrial stromal cells (HESCs).

METHODS

Primary HESCs were isolated from hysterectomy specimens and incubated with or without 8-bromo-cyclic adenosine monophosphate (8-br-cAMP) and medroxyprogesterone acetate (MPA).

RESULTS

We demonstrated that HMGN5 expression in decidualized HESCs stimulated by 8-br-cAMP and MPA decreased significantly. The inhibition of HMGN5 expression by small interfering RNA (siRNA) induced the major decidual marker genes expression, including IGFBP1 (insulin-like growth factor binding protein 1) and PRL (prolactin). In addition, microRNA-542-3p (miR-542-3p), which was identified as a regulatory miRNA of IGFBP1 during decidualization, was significantly suppressed by HMGN5 siRNA. However, the expression of HMGN5 was not alternated by miR-542-3p overexpression.

CONCLUSIONS

These findings suggest that the down-regulation of HMGN5 plays a role in the promotion of human endometrial stromal decidualization and acts upstream of miR-542-3p.

High mobility group A2 (HMGA2) promotes EMT via MAPK pathway in prostate cancer

Studies have shown that High mobility group A2 (HMGA2), a non-histone protein, can promote epithelial-mesenchymal transition (EMT), which plays a critical role in prostate cancer progression and metastasis. Interestingly, full-length or wild-type HMGA2 and truncated (lacking the 3'UTR) HMGA2 isoforms are overexpressed in several cancers. However, there are no studies investigating the expression and differential roles of WT vs truncated HMGA2 isoforms in prostate cancer. Immunohistochemical staining of prostate tissue microarray revealed low membrane expression in normal epithelial prostate cells, and that expression increased with tumor grade as well as a switch from predominantly cytoplasmic HMGA2 in lower tumor grades, to mostly nuclear in high grade and bone metastatic tissue. LNCaP cells stably overexpressing wild-type HMGA2 displayed nuclear localization of HMGA2 and induction of EMT associated with increased Snail, Twist and vimentin expression compared to LNCaP Neo control cells, as shown by immunofluorescence and western blot analyses. This was associated with increased cell migration on collagen shown using boyden chamber assay. Conversely, LNCaP cells overexpressing truncated HMGA2 showed cytoplasmic HMGA2 expression that did not induce EMT yet displayed increased cell proliferation and migration compared to LNCaP Neo. Both wild-type and truncated HMGA2 increased levels of phospho-ERK, and interestingly, treatment with U0126, MAPK inhibitor, antagonized wild-type HMGA2-mediated EMT and cell migration, but did not affect truncated HMGA2-mediated cell proliferation or migration. Therefore, although both wild-type and truncated HMGA2 may promote prostate tumor progression, wild-type HMGA2 acts by inducing EMT via MAPK pathway.

High-mobility group nucleosome binding domain 1 (HMGN1) functions as a Th1-polarizing alarmin

High-mobility group (HMG) nucleosome binding domain 1 (HMGN1), which previously was thought to function only as a nucleosome-binding protein that regulates chromatin structure, histone modifications, and gene expression, was recently discovered to be an alarmin that contributes extracellularly to the generation of innate and adaptive immune responses. HMGN1 promotes DC recruitment through interacting with a Gαi protein-coupled receptor (GiPCR) and activates DCs predominantly through triggering TLR4. HMGN1 preferentially promotes Th1-type immunity, which makes it relevant for the fields of vaccinology, autoimmunity, and oncoimmunology. Here, we discuss the alarmin properties of HMGN1 and update recent advances on its roles in immunity and potential applications for immunotherapy of tumors.

Hmgb3 Induces the Differentiation of Uterine Stromal Cells Through Targeting Ptn

Uterine decidualization is crucial for placenta formation and pregnancy maintenance. Although previous studies have reported that high mobility group box 3 (Hmgb3) is involved in the regulation of cellular proliferation and differentiation, little is known regarding its physiological role in uterine decidualization. Here, in situ hybridization result exhibited a dynamic expression pattern of Hmgb3 messenger RNA (mRNA) during early gestation, and it was mainly localized to the decidua on days 6 to 8 of gestation. Consistently, elevated Hmgb3 expression was noted in the decidualizing stromal cells after intraluminal oil infusion. In uterine luminal epithelium of ovariectomized mice, estrogen induced the accumulation of Hmgb3 mRNA, which was dependent on the existence of implanting blastocyst. Simultaneously, Hmgb3 could stimulate the proliferation of uterine stromal cells and promote the expression of Prl8a2, a reliable marker for stromal cell differentiation. Further analysis evidenced that Hmgb3 might modulate the expression of pleiotropin (Ptn) in uterine stromal cells. Moreover, silencing of Ptn could impede the upregulation of Prl8a2 elicited by Hmgb3 overexpression, while overexpression of Ptn reversed the repressive effects of Hmgb3 siRNA on Prl8a2 expression. Collectively, Hmgb3 may direct uterine decidualization through targeting Ptn.

Prognostic Value of HMGA2 in Human Cancers: A Meta-Analysis Based on Literatures and TCGA Datasets

Background: Emerging evidences have shown that the high-mobility group protein A2 (HMGA2) can aberrantly express in human cancers, and it could be an unfavorable prognostic factor in cancer patients. However, the prognostic value of HMGA2 was still unclear. Therefore, in this study, we explored the potential prognostic value of HMGA2 in human cancers by using meta-analysis based on published literatures and The Cancer Genome Atlas (TCGA) datasets.

Methods: Through searching PubMed, Embase, Web of Science and Cochrane Library databases, we were able to identify the studies evaluating the prognostic value of HMGA2 in cancers. Then, UALCAN and TCGA datasets were used to validate the results of our meta-analysis.

Results: In all, 15 types of cancers were included in this meta-analysis. Pooled results showed that high level of HMGA2 was significantly correlated with poor OS (HR = 1.88, 95% confidence interval (CI) = 1.68-2.11, P < 0.001) and poor DFS (HR = 2.49, 95% CI = 1.44-4.28, P = 0.001) in cancer patients. However, subgroup analyses revealed that the high expressed HMGA2 was associated with poor OS in head and neck cancer, gastric cancer and colorectal cancer, but not esophageal cancer and ovarian cancer. Based on TCGA datasets, we analyzed 9944 patients with 33 types of cancers. Significant association between HMGA2 overexpression and poor OS was found in 14 types of cancers. Taken together, consistent results were observed in clear cell renal cell carcinoma, esophageal adenocarcinoma, head and neck cancer, hepatocellular carcinoma, ovarian carcinoma, and pancreatic ductal adenocarcinoma.

Conclusion: Our meta-analysis showed the significance of HMGA2 and its prognostic value in various cancers. High level of HMGA2 could be associated with poor OS in patients with clear cell renal cell carcinoma, head and neck cancer, hepatocellular carcinoma and pancreatic ductal adenocarcinoma, but not esophageal adenocarcinoma and ovarian carcinoma.

New and Old Genes Associated with Primary and Established Responses to Paclitaxel Treatment in Ovarian Cancer Cell Lines

Development of drug resistance is the main reason for low chemotherapy effectiveness in treating ovarian cancer. Paclitaxel (PAC) is a chemotherapeutic drug used in the treatment of this cancer. We analysed the development of PAC resistance in two ovarian cancer cell lines. Exposure of drug-sensitive cell lines (A2780 and W1) to PAC was used to determine the primary response. An established response was determined in PAC-resistant sublines of the A2780 and W1 cell lines. qRT-PCR was performed to measure the expression levels of specific genes. We observed decreased expression of the PCDH9, NSBP1, MCTP1 and SEMA3A genes in the PAC-resistant cell lines. Short-term exposure to PAC led to increased expression of the MDR1 and BCRP genes in the A2780 and W1 cell lines. In the A2780 cell line, we also observed increased expression of the C4orf18 gene and decreased expression of the PCDH9 and SEMA3A genes after PAC treatment. In the W1 cell line, short-term treatment with PAC upregulated the expression of the ALDH1A1 gene, a marker of Cancer stem cells (CSCs). Our results suggest that downregulation of the PCDH9, NSBP1, MCTP1 and SEMA3A genes and upregulation of the MDR1, BCRP, C4orf18 and ALDH1A1 genes may be related to PAC resistance.

Lessons from the Crypt: HMGA1-Amping up Wnt for Stem Cells and Tumor Progression

High mobility group A1 (HMGA1) chromatin remodeling proteins are enriched in aggressive cancers and stem cells, although their common function in these settings has remained elusive until now. Recent work in murine intestinal stem cells (ISC) revealed a novel role for Hmga1 in enhancing self-renewal by amplifying Wnt signaling, both by inducing genes expressing Wnt agonist receptors and Wnt effectors. Surprisingly, Hmga1 also "builds" a stem cell niche by upregulating Sox9, a factor required for differentiation to Paneth cells; these cells constitute an epithelial niche by secreting Wnt and other factors to support ISCs. HMGA1 is also highly upregulated in colon cancer compared with nonmalignant epithelium and SOX9 becomes overexpressed during colon carcinogenesis. Intriguingly, HMGA1 is overexpressed in diverse cancers with poor outcomes, where it regulates developmental genes. Similarly, HMGA1 induces genes responsible for pluripotency and self-renewal in embryonic stem cells. These findings demonstrate that HMGA1 maintains Wnt and other developmental transcriptional networks and suggest that HMGA1 overexpression fosters carcinogenesis and tumor progression through dysregulation of these pathways. Studies are now needed to determine more precisely how HMGA1 modulates chromatin structure to amplify developmental genes and how to disrupt this process in cancer therapy. Cancer Res; 78(8); 1890-7. ©2018 AACR.

HMGB2 is associated with malignancy and regulates Warburg effect by targeting LDHB and FBP1 in breast cancer

Background

High-mobility group box 2 (HMGB2) is implicated in tumorigenesis in various cancers. However, the clinical significance of HMGB2 signaling in human breast cancer progression remains unknown.

Methods

We investigated HMGB2 expression in 185 cases of primary breast cancer and matched normal breast tissue specimens, and explored the underlying mechanisms of altered HMGB2 expression as well as the impact of this altered expression on breast cancer growth and on aerobic glycolysis using in vitro and animal models of breast cancer.

Results

HMGB2 was more highly expressed in tumor-cell nuclei of breast cancer cells than in the adjacent normal breast tissues (P < 0.05). Higher HMGB2 expression correlated with larger tumor size (P = 0.003) and advanced tumor stage (P = 0.033). A Cox proportional hazards model revealed that HMGB2 expression was an independent prognostic factor for breast cancer after radical resection (P < 0.05). Experimentally, knockdown of HMGB2 expression by stable transfected shRNA significantly decreased the growth and glycolysis of breast cancer cells both in vitro and in mouse models. Mechanically, promotion of breast cancer progression by HMGB2 directly and significantly correlated with activation of LDHB expression and inactivation of FBP1 expression.

Conclusions

These results disclose a novel role for HMGB2 in reprogramming the metabolic process in breast cancer cells by targeting LDHB and FBP1 and provide potential prognostic predictors for breast cancer patients.

Increased expression of high-mobility group nucleosomal-binding domain 2 protein in various tumor cell lines

High mobility group nucleosomal-binding domain 2 (HMGN2) is an abundant non-histone nuclear protein of vertebrates and invertebrates. The aim of the present study was to characterize the endogenous expression of HMGN2 in various types of tumor cell. Western blotting was performed to analyze HMGN2 expression in the following tumor cell lines: H1975, HSC-4, MDA-MB-468, MDA-MB-231, SCC-25 and THP-1. Periodontal ligament cells (PDLCs) were included as a noncancerous control. HMGN2 was detected in human oral squamous cell carcinoma tissues by immunohistochemical analysis. The results demonstrated that the expression of HMGN2 was increased in the majority of tumor cell lines, particularly MDA-MB-468 and THP-1 cells, compared with PDLCs. The expression of HMGN2 in oral squamous cell carcinoma tissue was significantly increased compared with the expression in normal tissue. Furthermore, the expression of HMGN2 in metastatic oral squamous cell carcinoma tissues was increased compared with that in its non-metastatic counterpart. These results indicated that HMGN2 may serve an important function in the growth and metastasis of tumor cells.

Binding of high mobility group A proteins to the mammalian genome occurs as a function of AT-content

Genomic location can inform on potential function and recruitment signals for chromatin-associated proteins. High mobility group (Hmg) proteins are of similar size as histones with Hmga1 and Hmga2 being particularly abundant in replicating normal tissues and in cancerous cells. While several roles for Hmga proteins have been proposed we lack a comprehensive description of their genomic location as a function of chromatin, DNA sequence and functional domains. Here we report such a characterization in mouse embryonic stem cells in which we introduce biotin-tagged constructs of wild-type and DNA-binding domain mutants. Comparative analysis of the genome-wide distribution of Hmga proteins reveals pervasive binding, a feature that critically depends on a functional DNA-binding domain and which is shared by both Hmga proteins. Assessment of the underlying queues instructive for this binding modality identifies AT richness, defined as high frequency of A or T bases, as the major criterion for local binding. Additionally, we show that other chromatin states such as those linked to cis-regulatory regions have little impact on Hmga binding both in stem and differentiated cells. As a consequence, Hmga proteins are preferentially found at AT-rich regions such as constitutively heterochromatic regions but are absent from enhancers and promoters arguing for a limited role in regulating individual genes. In line with this model, we show that genetic deletion of Hmga proteins in stem cells causes limited transcriptional effects and that binding is conserved in neuronal progenitors. Overall our comparative study describing the in vivo binding modality of Hmga1 and Hmga2 identifies the proteins’ preference for AT-rich DNA genome-wide and argues against a suggested function of Hmga at regulatory regions. Instead we discover pervasive binding with enrichment at regions of higher AT content irrespective of local variation in chromatin modifications.

We investigated the chromosomal location of a group of highly abundant nuclear proteins. Our genome-wide results for Hmga1 and Hmga2 reveal a unique binding modality indicating preference for DNA rich in A or T bases in vivo. Importantly this preferential binding to AT-rich sequences occurs throughout the genome irrespectively of other local chromatin features. Genomic location and loss of function experiments challenge the view that Hmga proteins act as local modulators of transcriptional regulation but rather argue for a role as structural components of chromatin.

Epigenetic Basis of Cellular Senescence and Its Implications in Aging

Cellular senescence is a tumor suppressive response that has become recognized as a major contributor of tissue aging. Senescent cells undergo a stable proliferative arrest that protects against neoplastic transformation, but acquire a secretory phenotype that has long-term deleterious effects. Studies are still unraveling the effector mechanisms that underlie these senescence responses with the goal to identify therapeutic interventions. Such effector mechanisms have been linked to the dramatic remodeling in the epigenetic and chromatin landscape that accompany cellular senescence. We discuss these senescence-associated epigenetic changes and their impact on the senescence phenotypes, notably the proliferative arrest and senescence associated secretory phenotype (SASP). We also explore possible epigenetic targets to suppress the deleterious effects of senescent cells that contribute towards aging.

Silencing HMGN5 suppresses cell growth and promotes chemosensitivity in esophageal squamous cell carcinoma

Previous study has demonstrated that high mobility group nucleosome-binding domain 5 (HMGN5) is involved in tumorigenesis and the development of multidrug resistance in several human cancers. However, the role of HMGN5 in esophageal squamous cell carcinoma (ESCC) remains unclear. Here, we showed that HMGN5 was significantly upregulated in ESCC cells. Knockdown of HMGN5 significantly inhibited cell growth and induced cell apoptosis of ESCC cells. Moreover, knockdown of HMGN5 increased the sensitivity of ESCC cells towards cisplatin. By contrast, overexpression of HMGN5 showed the opposite effects. Further experiments demonstrated that HMGN5 regulated the expression of multidrug resistance 1, cyclin B1, and Bcl-2. Overall, our results reveal that HMGN5 promotes tumor progression of ESCC and is also an important regulator of chemoresistance. Our study suggests that inhibition of HMGN5 may be a potential strategy for improving effectiveness of ESCC treatment.

Interplay between H1 and HMGN epigenetically regulates OLIG1&2 expression and oligodendrocyte differentiation

An interplay between the nucleosome binding proteins H1 and HMGN is known to affect chromatin dynamics, but the biological significance of this interplay is still not clear. We find that during embryonic stem cell differentiation loss of HMGNs leads to down regulation of genes involved in neural differentiation, and that the transcription factor OLIG2 is a central node in the affected pathway. Loss of HMGNs affects the expression of OLIG2 as well as that of OLIG1, two transcription factors that are crucial for oligodendrocyte lineage specification and nerve myelination. Loss of HMGNs increases the chromatin binding of histone H1, thereby recruiting the histone methyltransferase EZH2 and elevating H3K27me3 levels, thus conferring a repressive epigenetic signature at Olig1&2 sites. Embryonic stem cells lacking HMGNs show reduced ability to differentiate towards the oligodendrocyte lineage, and mice lacking HMGNs show reduced oligodendrocyte count and decreased spinal cord myelination, and display related neurological phenotypes. Thus, the presence of HMGN proteins is required for proper expression of neural differentiation genes during embryonic stem cell differentiation. Specifically, we demonstrate that the dynamic interplay between HMGNs and H1 in chromatin epigenetically regulates the expression of OLIG1&2, thereby affecting oligodendrocyte development and myelination, and mouse behavior.

Proteins Recognizing DNA: Structural Uniqueness and Versatility of DNA-Binding Domains in Stem Cell Transcription Factors

Proteins in the form of transcription factors (TFs) bind to specific DNA sites that regulate cell growth, differentiation, and cell development. The interactions between proteins and DNA are important toward maintaining and expressing genetic information. Without knowing TFs structures and DNA-binding properties, it is difficult to completely understand the mechanisms by which genetic information is transferred between DNA and proteins. The increasing availability of structural data on protein-DNA complexes and recognition mechanisms provides deeper insights into the nature of protein-DNA interactions and therefore, allows their manipulation. TFs utilize different mechanisms to recognize their cognate DNA (direct and indirect readouts). In this review, we focus on these recognition mechanisms as well as on the analysis of the DNA-binding domains of stem cell TFs, discussing the relative role of various amino acids toward facilitating such interactions. Unveiling such mechanisms will improve our understanding of the molecular pathways through which TFs are involved in repressing and activating gene expression.

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.

Association between HMGB1 and asthma: a literature review

Background

Recently, some studies demonstrated that HMGB1, as proinflammatory mediator belonging to the alarmin family, has a key role in different acute and chronic immune disorders. Asthma is a complex disease characterised by recurrent and reversible airflow obstruction associated to airway hyper-responsiveness and airway inflammation.

Objective

This literature review aims to analyse advances on HMGB1 role, employment and potential diagnostic application in asthma.

Methods

We reviewed experimental studies that investigated the pathogenetic role of HMGB in bronchial airway hyper-responsiveness, inflammation and the correlation between HMGB1 level and asthma.

Results

A total of 19 studies assessing the association between HMGB1 and asthma were identified.

Conclusions

What emerged from this literature review was the confirmation of HMGB-1 involvement in diseases characterised by chronic inflammation, especially in pulmonary pathologies. Findings reported suggest a potential role of the alarmin in being a stadiation method and a marker of therapeutic efficacy; finally, inhibiting HMGB1 in humans in order to contrast inflammation should be the aim for future further studies.

Role of Nhp6 and Hmo1 in SWI/SNF occupancy and nucleosome landscape at gene regulatory regions

Diverse chromatin modifiers are involved in regulation of gene expression at the level of transcriptional regulation. Among these modifiers are ATP-dependent chromatin remodelers, where the SWI/SNF complex is the founding member. It has been observed that High Mobility Group (HMG) proteins can influence the activity of a number of these chromatin remodelers. In this context, we have previously demonstrated that the yeast HMG proteins Nhp6 and Hmo1 can stimulate SWI/SNF activity. Here, we studied the genome-wide binding patterns of Nhp6, Hmo1 and the SWI/SNF complex, finding that most of gene promoters presenting high occupancy of this complex also display high enrichment of these HMG proteins. Using deletion mutant strains we demonstrate that binding of SWI/SNF is significantly reduced at numerous genomic locations by deletion of NHP6 and/or deletion of HMO1. Moreover, alterations in the nucleosome landscape take place at gene promoters undergoing reduced SWI/SNF binding. Additional analyses show that these effects also correlate with alterations in transcriptional activity. Our results suggest that, besides the ability to stimulate SWI/SNF activity, these HMG proteins are able to assist the loading of this complex onto gene regulatory regions.

MicroRNA-409-3p Represses Glioma Cell Invasion and Proliferation by Targeting High-Mobility Group Nucleosome-Binding Domain 5

Emerging evidence has suggested that aberrantly expressed microRNAs (miRNAs) are associated with glioma development and progression. The aberrant expression of miR-409-3p has been reported in several human cancers. However, little is known about the function of miR-409-3p in gliomas. The aim of this study was to investigate the specific role and molecular mechanism of miR-409-3p in gliomas. In the present study, we found that miR-409-3p was downregulated in glioma tissue and cell lines. Overexpression of miR-409-3p inhibited glioma cell invasion and proliferation, whereas suppression of miR-409-3p promoted glioma cell invasion and proliferation. High-mobility group nucleosome-binding domain 5 (HMGN5), a well-known oncogene in gliomas, was identified as a functional target of miR-409-3p using bioinformatics, dual-luciferase reporter assay, real-time quantitative polymerase chain reaction, and Western blot analysis. Furthermore, miR-409-3p was found to regulate the expression of matrix metalloproteinase 2 and cyclin D1. Restoration of HMGN5 expression significantly reversed the inhibitory effects of miR-409-3p overexpression on glioma cell invasion and proliferation. Taken together, our results suggest that miR-409-3p inhibits glioma cell invasion and proliferation by targeting HMGN5, representing a potential therapeutic target for glioma.

The High Mobility Group A1 (HMGA1) Transcriptome in Cancer and Development

BACKGROUND & OBJECTIVES

Chromatin structure is the single most important feature that distinguishes a cancer cell from a normal cell histologically. Chromatin remodeling proteins regulate chromatin structure and high mobility group A (HMGA1) proteins are among the most abundant, nonhistone chromatin remodeling proteins found in cancer cells. These proteins include HMGA1a/HMGA1b isoforms, which result from alternatively spliced mRNA. The HMGA1 gene is overexpressed in cancer and high levels portend a poor prognosis in diverse tumors. HMGA1 is also highly expressed during embryogenesis and postnatally in adult stem cells. Overexpression of HMGA1 drives neoplastic transformation in cultured cells, while inhibiting HMGA1 blocks oncogenic and cancer stem cell properties. Hmga1 transgenic mice succumb to aggressive tumors, demonstrating that dysregulated expression of HMGA1 causes cancer in vivo. HMGA1 is also required for reprogramming somatic cells into induced pluripotent stem cells. HMGA1 proteins function as ancillary transcription factors that bend chromatin and recruit other transcription factors to DNA. They induce oncogenic transformation by activating or repressing specific genes involved in this process and an HMGA1 "transcriptome" is emerging. Although prior studies reveal potent oncogenic properties of HMGA1, we are only beginning to understand the molecular mechanisms through which HMGA1 functions. In this review, we summarize the list of putative downstream transcriptional targets regulated by HMGA1. We also briefly discuss studies linking HMGA1 to Alzheimer's disease and type-2 diabetes.

CONCLUSION

Further elucidation of HMGA1 function should lead to novel therapeutic strategies for cancer and possibly for other diseases associated with aberrant HMGA1 expression.