Matrix Attachment Regions Research Articles

Matrix attachment regions enhance transgene expression by manipulating position-dependent effects in stably transfected CHO-K1 cells.

We previously found that the position of matrix attachment regions (MARs) within the vector significantly affects its ability to enhance transgenic expression in the recombinant protein production. This study aims to systematically investigate the position-dependent impacts of MAR on transgene expression. We observed a significant increase in enhanced green fluorescent protein (eGFP) expression levels in stably transfected CHO-K1 cells with either MAR 1-68 or MAR X-29 when MARs located upstream of the promoter. This increase was especially evident with MAR flanked the expression cassette. Concurrently, a substantial increase was observed in the percentage of eGFP-expressing cells, with 97.8% and 96.0% in MAR-containing constructs versus 73.7% in MAR-absent constructs. Further analysis of erythropoietin (EPO) expression revealed that constructs with flanking MARs induced the highest EPO productivity. Bioinformatics analysis revealed that certain specific transcription factors are important in modulating the transcription process. In conclusion, vectors harboring both MARs around the expression cassette constitute an optimal construct for enhanced recombinant protein production in CHO-K1 cells. This insight underscores the importance of strategic MAR incorporation in vector design for optimized recombinant protein expression.

Research progress on the effect of sperm chromatin integrity on function and its detection methods.

Sperm chromatin not only carries genetic information such as paternal DNA, but also carries structural proteins, epigenetic information, and higher-order chromatin structures (such as matrix attachment regions and telomeres), etc. These information play an important role in embryonic development. This article mainly reviews the effects of these different information carried by sperm chromatin on sperm function and embryonic development and the research progress of related detection methods, in order to provide a theoretical basis and scientific diagnosis and treatment strategies for the etiology screening of clinical infertility, embryo arrest and recurrent miscarriage, so as to improve the pregnancy outcomes of natural conception and assisted reproduction. Keywords: sperm chromatin; epigenetics; sperm DNA damage; sperm function; higher-order chromatin structures.

Recombinant Protein Expression Optimizing: A Review of S/MAR, STAR, and UCOE, as a Chromatin-Modifying Element

The rapid growth of the global biopharmaceutical market in recent years indicates its importance in the biotechnology industry. The production of these medicinal products is one of the fastest-growing industries in the patient treatment field. Since 1980, processes have been developed to optimize the production of recombinant protein products upstream and downstream. In this regard, one promising approach is the engineering of expression vectors based on combinations of DNA regulatory elements found in euchromatin regions. This approach aims to achieve proper gene integration and facilitate its expression in the target cell, as epigenetic mechanisms can lead to instability of the desired gene in long-term cell cultures and gene silencing. To address this issue, genetically engineered vectors have been produced, which include components such as Matrix Attachment Regions (MARs), Scaffold Attachment Regions (SARs), Stabilizing Anti-Repressor Elements (STAREs), and Ubiquitous Chromatin Opening Elements (UCOE). These components can modify the chromatin environment to minimize gene silencing and enhance higher, more stable, and biologically active expression of recombinant molecules. In this review, we focus on different approaches and developments in the technology of expression vector engineering and their impact on increasing the production of recombinant proteins.

Design and validation of a reporter mouse to study the dynamic regulation of TFEB and TFE3 activity through in vivo imaging techniques

ABSTRACT TFEB and TFE3 belong to the MiT/TFE family of transcription factors that bind identical DNA responsive elements in the regulatory regions of target genes. They are involved in regulating lysosomal biogenesis, function, exocytosis, autophagy, and lipid catabolism. Precise control of TFEB and TFE3 activity is crucial for processes such as senescence, stress response, energy metabolism, and cellular catabolism. Dysregulation of these factors is implicated in various diseases, thus researchers have explored pharmacological approaches to modulate MiT/TFE activity, considering these transcription factors as potential therapeutic targets. However, the physiological complexity of their functions and the lack of suitable in vivo tools have limited the development of selective MiT/TFE modulating agents. Here, we have created a reporter-based biosensor, named CLEARoptimized, facilitating the pharmacological profiling of TFEB- and TFE3-mediated transcription. This innovative tool enables the measurement of TFEB and TFE3 activity in living cells and mice through imaging and biochemical techniques. CLEARoptimized consists of a promoter with six coordinated lysosomal expression and regulation motifs identified through an in-depth bioinformatic analysis of the promoters of 128 TFEB-target genes. The biosensor drives the expression of luciferase and tdTomato reporter genes, allowing the quantification of TFEB and TFE3 activity in cells and in animals through optical imaging and biochemical assays. The biosensor’s validity was confirmed by modulating MiT/TFE activity in both cell culture and reporter mice using physiological and pharmacological stimuli. Overall, this study introduces an innovative tool for studying autophagy and lysosomal pathway modulation at various biological levels, from individual cells to the entire organism. Abbreviations: CLEAR: coordinated lysosomal expression and regulation; MAR: matrix attachment regions; MiT: microphthalmia-associated transcription factor; ROI: region of interest; TBS: tris-buffered saline; TF: transcription factor; TFE3: transcription factor binding to IGHM enhancer 3; TFEB: transcription factor EB; TH: tyrosine hydroxylase; TK: thymidine kinase; TSS: transcription start site.

Chromatin attachment to the nuclear matrix represses hypocotyl elongation in Arabidopsis thaliana

The nuclear matrix is a nuclear compartment that has diverse functions in chromatin regulation and transcription. However, how this structure influences epigenetic modifications and gene expression in plants is largely unknown. In this study, we show that a nuclear matrix binding protein, AHL22, together with the two transcriptional repressors FRS7 and FRS12, regulates hypocotyl elongation by suppressing the expression of a group of genes known as SMALL AUXIN UP RNAs (SAURs) in Arabidopsis thaliana. The transcriptional repression of SAURs depends on their attachment to the nuclear matrix. The AHL22 complex not only brings these SAURs, which contain matrix attachment regions (MARs), to the nuclear matrix, but it also recruits the histone deacetylase HDA15 to the SAUR loci. This leads to the removal of H3 acetylation at the SAUR loci and the suppression of hypocotyl elongation. Taken together, our results indicate that MAR-binding proteins act as a hub for chromatin and epigenetic regulators. Moreover, we present a mechanism by which nuclear matrix attachment to chromatin regulates histone modifications, transcription, and hypocotyl elongation.

Non-Viral Episomal Vector Mediates Efficient Gene Transfer of the β-Globin Gene into K562 and Human Haematopoietic Progenitor Cells.

β-Thalassemia is a subgroup of inherited blood disorders associated with mild to severe anemia with few and limited conventional therapy options. Lately, lentiviral vector-based gene therapy has been successfully applied for disease treatment. However, the current development of non-viral episomal vectors (EV), non-integrating and non-coding for viral proteins, may be helpful in generating valid alternatives to viral vectors. We constructed a non-viral, episomal vector pEPβ-globin for the physiological β-globin gene based on two human chromosomal elements: the scaffold or matrix attachment region (S/MAR), allowing for long nuclear retention and non-integration and the β-globin replication initiation region (IR), allowing for enhancement of replication and establishment. After nucleofections into K562 cells with a transfection efficiency of 24.62 ± 7.7%, the vector induces stable transfection and is detected in long-term cultures as a non-integrating, circular episome expressing the β-globin gene efficiently. Transfections into CD34+ cells demonstrate an average efficiency of 15.57 ± 11.64%. In the colony-forming cell assay, fluorescent colonies are 92.21%, which is comparable to those transfected with vector pEP-IR at 92.68%. Additionally, fluorescent colonies produce β-globin mRNA at a physiologically 3-fold higher level than the corresponding non-transfected cells. Vector pEPβ-globin provides the basis for the development of therapeutic EV for gene therapy of β-thalassemias.

Combination of MAR and intron increase transgene expression of episomal vectors in CHO cells.

Previous work has shown that the EF-1α promoter of episomal vectors maintains high-level transgene expression in stably transfected Chinese-hamster ovary (CHO) cells. However, the transgene expression levels need to be further increased. Here, we first incorporated matrix attachment regions (MAR), ubiquitous chromatin opening element (UCOE), stabilizing anti repressor elements 40 (STAR 40) elements into episomal vector at different sites and orientations, and systemically assessed their effects on transgene expression in transfected CHO-K1 cells. Results showed that enhanced green fluorescent protein (eGFP) expression levels increased remarkably when MAR X-29 was inserted upstream of the promoter, followed by the insertion of MAR-1 downstream of the poly A, and the orientation had no significant effect. Moreover, MAR X-29 combined with human cytomegalovirus intron (hCMVI) yielded the highest transgene expression levels (4.52-fold). Transgene expression levels were not exclusively dependent on transgene copy numbers and were not related to the mRNA expression level. In addition, vector with MAR X-29+ hCMVI can induce herpes simplex virus thymidine kinase (HSV-TK) protein expression, and the HSV-TK protein showed a cell-killing effect and an obvious bystander effect on HCT116 cells. In conclusion, the combination of MAR X-29 and hCMV intron can achieve high efficiency transgene expression mediated by episomal vectors in CHO-K1 cells. This article is protected by copyright. All rights reserved.

Structural insights into DNA recognition by the BEN domain of the transcription factor BANP

The BEN domain-containing transcription factors regulate transcription by recruiting chromatin-modifying factors to specific chromatin regions via their DNA-binding BEN domains. The BEN domain of BANP has been shown to bind to a CGCG DNA sequence or an AAA-containing matrix attachment regions DNA sequence. Consistent with these invivo observations, we identified an optimal DNA-binding sequence of AAATCTCG by protein binding microarray, which was also confirmed by our isothermal titration calorimetry and mutagenesis results. We then determined crystal structures of the BANP BEN domain in apo form and in complex with a CGCG-containing DNA, respectively, which revealed that the BANP BEN domain mainly used the electrostatic interactions to bind DNA with some base-specific interactions with the TC motifs. Our isothermal titration calorimetry results also showed that BANP bound to unmethylated and methylated DNAs with comparable binding affinities. Our complex structure of BANP-mCGCG revealed that the BANP BEN domain bound to the unmethylated and methylated DNAs in a similar mode and cytosine methylation did not get involved in binding, which is also consistent with our observations from the complex structures of the BEND6 BEN domain with the CGCG or CGmCG DNAs. Taken together, our results further elucidate the elements important for DNA recognition and transcriptional regulation by the BANP BEN domain-containing transcription factor.

ConFERMing the role of talin in integrin activation and mechanosignaling.

Talin (herein referring to the talin-1 form), is a cytoskeletal adapter protein that binds integrin receptors and F-actin, and is a key factor in the formation and regulation of integrin-dependent cell-matrix adhesions. Talin forms the mechanical link between the cytoplasmic domain of integrins and the actin cytoskeleton. Through this linkage, talin is at the origin of mechanosignaling occurring at the plasma membrane-cytoskeleton interface. Despite its central position, talin is not able to fulfill its tasks alone, but requires help from kindlin and paxillin to detect and transform the mechanical tension along the integrin-talin-F-actin axis into intracellular signaling. The talin head forms a classical FERM domain, which is required to bind and regulate the conformation of the integrin receptor, as well as to induce intracellular force sensing. The FERM domain allows the strategic positioning of protein-protein and protein-lipid interfaces, including the membrane-binding and integrin affinity-regulating F1 loop, as well as the interaction with lipid-anchored Rap1 (Rap1a and Rap1b in mammals) GTPase. Here, we summarize the structural and regulatory features of talin and explain how it regulates cell adhesion and force transmission, as well as intracellular signaling at integrin-containing cell-matrix attachment sites.

Abstract P6-11-01: Scaffold attachment factor B1 modulates cholesterol pathways in triple-negative breast cancer

Abstract Historically known as a tumor suppressor by estrogen receptor (ER) co-repression in breast cancer (BC), the matrix binding protein Scaffold Attachment Factor B1 (SAFB) binds scaffold or matrix attachment region DNA elements (S/MAR DNA) in eukaryotic DNA. SAFB1 plays a role in cellular stress response, DNA repair, differentiation, and apoptosis. SAFB loss in ER-independent BC and pancreatic cancer (PC) patients resulted in poor survival rates, hinting at the role of SAFB1 as a tumor suppressor. To understand the tumor suppressive mechanism of SAFB1, we performed shRNA-mediated knockdown (KD) of SAFB in PC cell lines and triple-negative breast cancer (TNBC) cells, an aggressive subgroup of BC. Analysis of onco-properties showed an increase in clonogenicity potential and cell proliferation in SAFB KDs in both PDACs and TNBCs cells. Further, RNA-Seq analysis of SAFB KDs in the TNBC cell line revealed activation of the mevalonate (MVA) pathway and the resulting cholesterol biosynthesis as the key metabolic change. Both pancreatic ductal adenocarcinoma (PDACs) and TNBC exhibited higher levels of MVA pathway gene expression upon loss of SAFB. Sterol regulatory element binding proteins (SREBP) 1 and 2 dictate cholesterol biosynthesis, and SREBP2 promotes tumor properties via the MVA pathway. Molecular and metabolic analysis of SAFB KD TNBC showed an increase in lipid droplets and SREBP2 maturation. Using Chromatin Immunoprecipitation and quantitative real-time PCR (ChIP-qPCR) in TNBC we demonstrate the direct binding of SAFB to the SREBP2 promoter region. In addition, byproducts of the MVA pathway have been shown to activate YAP/TAZ-dependent tissue homeostasis and tumorigenesis. We also observed increased YAP1 mRNA levels and decreased YAP1 (Ser127) phosphorylation with SAFB loss in TNBC, explaining the aggressive tumorigenicity gained with SAFB loss. Our study thus far suggests SAFB has overt control over the SREBP2-MVA-YAP1 pathway, and loss of SAFB results in an enhanced tumor phenotype. Citation Format: Meron Ghidey, Divya Murthy, Sukjin Yang, Songyeon Ahn, Jun Hyoung Park, Benny Kaipparettu. Scaffold attachment factor B1 modulates cholesterol pathways in triple-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-11-01.

Design of an artificial transcriptional system for production of high levels of recombinant proteins in tobacco (Nicotiana benthamiana).

Plants have recently received much attention as a means of producing recombinant proteins because they are easy to grow at a low cost and at a large scale. Although many plant protein expression systems have been developed, there remains a need for improved systems that deliver high yields of recombinant proteins. Transcription of the recombinant gene is a key step in increasing the yield of recombinant proteins. However, revealed strong promoters, terminators, and transcription factors that have been identified do not necessarily lead to high level production of recombinant proteins. Thus, in this study, a robust expression system was designed to produce high levels of recombinant protein consisting of a novel hybrid promoter, FM'M-UD, coupled with an artificial terminator, 3PRt. FM'M-UD contained fragments from three viral promoters (the promoters of Mirabilis mosaic caulimovirus (MMV) full-length transcript, the MMV subgenomic transcript, and figwort mosaic virus subgenomic transcript) and two types of cis-acting elements (four GAL4 binding sites and two zinc finger binding sites). The artificial terminator, 3PRt, consisted of the PINII and 35S terminators plus RB7, a matrix attachment region. The FM'M-UD promoter increased protein levels of reporters GFP, RBD : SD1 (part of S protein from SARS-CoV-2), and human interleukin-6 (hIL6) by 4-6-fold, 2-fold, and 6-fold, respectively, relative to those of the same reporters driven by the CaMV 35S promoter. Furthermore, when the FM'M-UD/3PRt expression cassette was expressed together with GAL4/TAC3d2, an artificial transcription factor that bound the GAL4 binding sites in FM'M-UD, levels of hIL6 increased by 10.7-fold, relative to those obtained from the CaMV 35S promoter plus the RD29B terminator. Thus, this novel expression system led to the production of a large amount of recombinant protein in plants.

Comprehensive in silico analysis of Phospholipase D gene family in economically important orchids

• A total of 25 putative PLD proteins from the genomes of Phalaenopsis equestris (7) , Dendrobium catenatum (9) and Apostasia shenzhenica (9) were identified. • These proteins are comprised of two HKD domains and two additional domains; C2 and PXPH domains at N-terminal region. • The multiple sequence alignment, domain and motifs analysis revealed their conserved nature and homology structure simulation and Ramachadran plot analysis revealed the abundance of beta sheets in tertiary structures. • The presence of Root-specific element, DOF proteins binding domain, scaffold or matrix attachment region, pollen-specific, dehydration-responsive, light-responsive, gibberellin-responsive, ABA-responsive elements and Meja-responsive upstream cis- regulatory promoter elements indicated their role in various physiological processes. Phospholipase D (PLD) plays a fundamental role in various aspects of plant growth, development and stress responses. In present study, 25 putative PLD proteins from the genomes of Phalaenopsis equestris (7) , Dendrobium catenatum (9) and Apostasia shenzhenica (9) were identified on the basis of presence of two HKD domains and two additional domains; C2 and PXPH domains at N-terminal region. These proteins were clustered into five sub-groups (α, β, δ, ζ and φ) along with their orthologs in Arabidopsis thaliana and Oryza sativa upon phylogenetic analysis. Gene characterization divulged that most of the PePLD, DcPLD and AsPLD genes within the same sub-group exhibited similar exon-intron organization and highly conserved motifs. RNA-seq based spatio-temporal studies indicated differential expression in various vegetative and reproductive tissues. PePLDα 1 , DcPLDα 1 and AsPLDα 1 were showing significant expression in all the tissues, while for other genes the expression was limited either in vegetative or reproductive tissues. Homology structure simulation revealed the abundance of random coils in secondary structures and beta sheets in tertiary structures. The presence of specific upstream cis- regulatory promoter elements emphasized the role of PLD s in various physiological processes. This report is the first genome-wide characterization of the PLD gene family in orchids and shall provide new insight into the functional characterization of these genes.

Structural and developmental dynamics of Matrix associated regions in Drosophila melanogaster genome

BackgroundEukaryotic genome is compartmentalized into structural and functional domains. One of the concepts of higher order organization of chromatin posits that the DNA is organized in constrained loops that behave as independent functional domains. Nuclear Matrix (NuMat), a ribo-proteinaceous nucleoskeleton, provides the structural basis for this organization. DNA sequences located at base of the loops are known as the Matrix Attachment Regions (MARs). NuMat relates to multiple nuclear processes and is partly cell type specific in composition. It is a biochemically defined structure and several protocols have been used to isolate the NuMat where some of the steps have been critically evaluated. These sequences play an important role in genomic organization it is imperative to know their dynamics during development and differentiation.ResultsHere we look into the dynamics of MARs when the preparation process is varied and during embryonic development of D. melanogaster. A subset of MARs termed as “Core-MARs” present abundantly in pericentromeric heterochromatin, are constant unalterable anchor points as they associate with NuMat through embryonic development and are independent of the isolation procedure. Euchromatic MARs are dynamic and reflect the transcriptomic profile of the cell. New MARs are generated by nuclear stabilization, and during development, mostly at paused RNA polymerase II promoters. Paused Pol II MARs depend on RNA transcripts for NuMat association.ConclusionsOur data reveals the role of MARs in functionally dynamic nucleus and contributes to the current understanding of nuclear architecture in genomic context.

SMAR1 inhibits proliferation, EMT and Warburg effect of bladder cancer cells by suppressing the activity of the Wnt/β-catenin signaling pathway

ABSTRACT This study aimed to investigate the effects of scaffold matrix attachment region binding protein 1 (SMAR1) on the development of bladder cancer (BCa). SMAR1 expression in paired tumor and corresponding adjacent normal tissues from 55 BCa patients was detected by quantitative reverse transcription-polymerase chain reaction. BCa cells were transfected to regulate SMAR1 expression. BCa cells were treated with XAV-939, LiCl and 2-deoxyglucose. The effect of SMAR1 on the viability, proliferation, migration, invasion and Warburg effect of BCa cells was researched by counting kit-8, colony formation assay, Transwell and aerobic glycolysis assays. Western blot was performed to detect protein expression. BCa cell growth in vivo was recorded in nude mice. Immunohistochemical staining was performed for clinical and xenografted tumor tissue specimens. SMAR1 expression was down-regulated in BCa patients, associating with worse prognoses. SMAR1 knockdown enhanced the viability, proliferation, migration, invasion, EMT and Warburg effect of BCa cells. The opposite effect was found in the SMAR1 overexpression BCa cells. XAV-939 treatment reversed the elevation of β-catenin, c-Myc and Cyclin D1 proteins expression and Warburg effect in Bca cells post-SMAR1 knockdown. LiCl treatment abrogated the inhibition of β-catenin, c-Myc and Cyclin D1 proteins expression and Warburg effect proteins due to SMAR1 overexpression in BCa cells. SMAR1 overexpression inhibited the growth of BCa cells in vivo. SMAR1 might suppress the Wnt/β-catenin signaling pathway activity to inhibit the progression of BCa. It might be an effective treatment target for BCa.

Generation of a host cell line containing a MAR-rich landing pad for site-specific integration and expression of transgenes.

In recent years, targeted gene integration (TI) has been introduced as a strategy for the generation of recombinant mammalian cell lines for the production of biotherapeutics. Besides reducing the immense heterogeneity within a pool of recombinant transfectants, TI also aims at shortening the duration of the current cell line development process. Here we describe the generation of a host cell line carrying Matrix‐Attachment Region (MAR)‐rich landing pads (LPs), which allow for the simultaneous and site‐specific integration of multiple genes of interest (GOIs). We show that several copies of each chicken lysozyme 5'MAR‐based LP containing either BxB1 wild type or mutated recombination sites, integrated at one random chromosomal locus of the host cell genome. We further demonstrate that these LP‐containing host cell lines can be used for the site‐specific integration of several GOIs and thus, generation of transgene‐expressing stable recombinant clones. Transgene expression was shown by site‐specific integration of heavy and light chain genes coding for a monospecific antibody (msAb) as well as for a bi‐specific antibody (bsAb). The genetic stability of the herein described LP‐based recombinant clones expressing msAb or bsAb was demonstrated by cultivating the recombinant clones and measuring antibody titers over 85 generations. We conclude that the host cell containing multiple copies of MAR‐rich landing pads can be successfully used for stable expression of one or several GOIs.

Dynamics of nuclear matrix attachment regions during 5th instar posterior silk gland development in Bombyx mori

BackgroundChromatin architecture is critical for gene expression during development. Matrix attachment regions (MARs) control and regulate chromatin dynamics. The position of MARs in the genome determines the expression of genes in the organism. In this study, we set out to elucidate how MARs temporally regulate the expression of the fibroin heavy chain (FIBH) gene during development. We addressed this by identifying MARs and studying their distribution and differentiation, in the posterior silk glands of Bombyx mori during 5th instar development.ResultsOf the MARs identified on three different days, 7.15% MARs were common to all 3 days, whereas, 1.41, 19.27 and 52.47% MARs were unique to day 1, day 5, and day 7, respectively highlighting the dynamic nature of the matrix associated DNA. The average chromatin loop length based on the chromosome wise distribution of MARs and the distances between these MAR regions decreased from day 1 (253.91 kb) to day 5 (73.54 kb) to day 7 (39.19 kb). Further significant changes in the MARs in the vicinity of the FIBH gene were found during different days of 5th instar development which implied their role in the regulation and expression of the FIBH gene.ConclusionsThe presence of MARs in the flanking regions of genes found to exhibit differential expression during 5th instar development indicates their possible role in the regulation of their expression. This reiterates the importance of MARs in the genomic functioning as regulators of the molecular mechanisms in the nucleus. This is the first study that takes into account the tissue specific genome-wide MAR association and the potential role of these MARs in developmentally regulated gene expression. The current study lays a foundation to understand the genome wide regulation of chromatin during development.

Chromatin Reorganization during Myoblast Differentiation Involves the Caspase-Dependent Removal of SATB2.

The induction of lineage-specific gene programs are strongly influenced by alterations in local chromatin architecture. However, key players that impact this genome reorganization remain largely unknown. Here, we report that the removal of the special AT-rich binding protein 2 (SATB2), a nuclear protein known to bind matrix attachment regions, is a key event in initiating myogenic differentiation. The deletion of myoblast SATB2 in vitro initiates chromatin remodeling and accelerates differentiation, which is dependent on the caspase 7-mediated cleavage of SATB2. A genome-wide analysis indicates that SATB2 binding within chromatin loops and near anchor points influences both loop and sub-TAD domain formation. Consequently, the chromatin changes that occur with the removal of SATB2 lead to the derepression of differentiation-inducing factors while also limiting the expression of genes that inhibit this cell fate change. Taken together, this study demonstrates that the temporal control of the SATB2 protein is critical in shaping the chromatin environment and coordinating the myogenic differentiation program.

Quantification of Epigenetic DNA Modifications in the Subchromatin Structure Matrix Attachment Regions by Stable Isotope Dilution UHPLC-MS/MS Analysis.

To date, subchromatin structure-based quantification of epigenetic DNA modifications is limited. Matrix attachment regions (MARs), an important subchromatin structure, contain DNA elements that specifically bind chromatin to the nuclear matrix in eukaryotes and are involved in a number of diseases. Here, we exploited a high-salt extraction-based subchromatin fractionation approach for the isolation of MAR DNA and other fractions and further developed heavy stable isotope-diluted ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) for the specific quantification of epigenetic DNA modifications in the subchromatin structures. By this approach, we showed for the first time that the content of a DNA demethylation intermediate, 5-hydroxymethylcytosine (5hmdC), in MARs decreased significantly in four tested cell lines compared to the contents in genomic DNA. In particular, the content of DNA 5hmdC in the MARs of 293T cell lines decreased the most at approximately 41.09%. Together, our findings implicate that MAR DNA is less sensitive than genomic DNA to DNA demethylation.

SATB2 expression in human tumors: A tissue microarray study on more than 15,000 tumors

Abstract Introduction/Objective Introduction: Special AT-rich sequence-binding protein 2 (SATB2) binds to DNA in specific nuclear matrix attachment regions and facilitates chromatin remodeling. SATB2 immunostaining is commonly used as a marker for colorectal adenocarcinoma and osteosarcoma. Methods/Case Report Methods: To comprehensively evaluate SATB2 expression in normal and tumor tissues, a tissue microarray containing 15,012 samples from 120 different tumor types and subtypes and 608 samples of 76 different normal tissue types were analyzed by immunohistochemistry. Results (if a Case Study enter NA) Result: SATB2 positivity was found in 89 different tumor types including 59 with at least one moderately positive and 38 tumor types with at least one strongly positive tumor. Most frequent and strongest expression were found in adenomas (94-96%), adenocarcinomas (86%) and various subtypes of neuroendocrine neoplasms (43-100%) of the colorectum and appendix, Merkel cell carcinoma (74%), osteosarcomas (60%), and papillary renal cell carcinoma (RCC) (52%). In colorectal cancer, weak SATB2 expression was linked to high pT (p<0.0001), nodal metastasis (p<0.0001), right-sided tumor location (p<0.0001), microsatellite instability (p=0.0004), and BRAF mutations (p<0.0224). In papillary RCC, low SATB2 was associated with high pT (p=0.0197), distant metastasis (p=0.042), and reduced tumor specific survival (p=0.0395). In clear cell RCC, low SATB2 was linked to high pT (p<0.0001), high UICC stage (p<0.0001), high Thoenes grade (p=0.0178), and reduced recurrence free survival (p=0.0216). Conclusion SATB2 expression can occur in many different tumor entities. Strong SATB2 expression argues for a colorectal tumor origin within adenocarcinomas and neuroendocrine neoplasms. Weak SATB2 expression reflects cancer progression and poor prognosis in colorectal and kidney cancer.

35. CELL-TYPE-SPECIFIC PATTERNS OF DNA METHYLATION IN THE DEVELOPING HUMAN BRAIN

Matrix attachment region (MAR)-binding protein (MARBP) has profound influence on gene transcriptional control by tethering genes to the nuclear scaffold. MARBP SATB2 is recently known as a versatile regulator functioning in the differentiation of multiple cell types including embryonic stem cells, osteoblasts and immunocytes. Roles of SATB2 in erythroid cells and its working mechanism in orchestrating target gene expression are largely unexplored. We show here that SATB2 is expressed in erythroid cells and activates γ-globin genes by binding to MARs in their promoters and recruiting histone acetylase PCAF. Further analysis in higher-order chromatin structure shows that SATB2 affects physical proximity of human Gγ- and Aγ-globin promoters via self-association. We also found that SATB2 interacts with SATB1, which specifically activates ϵ-globin gene expression. Our results establish SATB2 as a novel γ-globin gene regulator and provide a glimpse of the differential and cooperative roles of SATB family proteins in modulating clustered genes transcription and mediating higher-order chromatin structures.