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Genomic structure of BORG. A, the linear map of the gene structure is shown. Three exons are indicated by shaded boxes. The location of restriction enzyme sites is shown with abbreviations: E, EcoRI; S, SacI. B, exon-intron boundaries of BORG. Exon and intron sequences are indicated by uppercase and lowercase letters, respectively . The approximate sizes of each intron are shown in parentheses. Conserved dinucleotides are indicated in boldface.
Source publication
Bone morphogenetic proteins (BMPs)/osteogenic proteins (OPs), members of the transforming growth factor-beta superfamily, have a wide variety of effects on many cell types including osteoblasts and chondroblasts, and play critical roles in embryonic development. BMPs transduce their effects through binding to two different types of serine/threonine...
Citations
... The bone morphogenetic proteins (BMP)/OPresponsive gene (BORG) represents a commonly targeted gene by BMPs. In the C2C12 mouse myoblast cell line, transfection with antisense oligonucleotides targeting BORG partially inhibited BMP-induced alkaline phosphatase activity, thereby impeding the differentiation of C2C12 cells into osteoblasts [52]. Nkx2.2 is a pivotal TF involved in the differentiation of neural stem cells into oligodendrocytes [53]. ...
... Similarly, maintenance of BCSC populations is contingent upon the niche in which they reside, as an optimized compendium of paracrine factors, ECM organization, and vascular and immune effector cells coalesce in permitting BCSC self-renewal and preventing their terminal differentiation (71). Interestingly, BORG expression is regulated by these same stromal components, including paracrine signals (e.g., TGF-, BMP2, and BMP7), hypoxia, nutrient deprivation, and mechanotransduction by the ECM (18,19,72). It therefore stands to reason that BORG, despite being solely localized to the nucleus (21), may function as an essential effector molecule that underlies the plasticity of BCSCs in response to evolving niche-derived signals, thereby enhancing the stemness and metastatic ability of BCSCs via its ability to induce 6 integrin and enhance ECM communication. ...
Triple-negative breast cancer (TNBC) is the most lethal subtype of breast cancer, with its aggressive phenotype being attributed to chemotherapy resistance, metastatic dissemination, and rapid disease recurrence. Breast cancer stem cells (BCSC) are significant contributors to tumor initiation, as well as to the acquisition of aggressive tumorigenic phenotypes, namely due to their ability to self-replicate and to produce heterogeneous differentiated tumor cells. To elucidate the underlying mechanisms that drive BCSC tumorigenicity in TNBC, we identified the long noncoding RNA (lncRNA) BMP/OP-Responsive Gene (BORG) as an enhancer of BCSC phenotypes. Indeed, we found BORG expression to: (i) correlate with stem cell markers Nanog, Aldh1a3, and Itga6 (α6 integrin/CD49f); (ii) enhance stem cell phenotypes in murine and human TNBC cells, and (iii) promote TNBC tumor initiation in mice. Mechanistically, BORG promoted BCSC phenotypes through its ability to interact physically with the E3 SUMO ligase TRIM28. Moreover, TRIM28 binding was observed in the promoter region of Itga6, whose genetic inactivation prevented BORG:TRIM28 complexes from: (i) inducing BCSC self-renewal and expansion in vitro, and (ii) eliciting BCSC metastatic outgrowth in the lungs of mice. Collectively, these findings implicate BORG:TRIM28 complexes as novel drivers of BCSC phenotypes in developing and progressing TNBCs.
Implications
This work establishes the lncRNA BORG as a driver of BCSC phenotypes and the aggressive behaviors of TNBCs, events critically dependent upon the formation of BORG:TRIM28 complexes and expression of α6 integrin.
... The spliced and polyadenylated lncRNA BORG regulates BMPinduced differentiation of C2C12 cells into osteoblastic cells and is exclusively localized to the nucleus (Takeda et al., 1998). The nuclear localization of BORG is mediated by a short AGCCC RNA motif. ...
The number of long noncoding RNAs (lncRNAs) with characterized developmental and cellular functions continues to increase, but our understanding of the molecular mechanisms underlying lncRNA functions, and how they are dictated by RNA sequences, remains limited. Relatively short, conserved sequence motifs embedded in lncRNA transcripts are often important determinants of lncRNA localization, stability and interactions. Identifying such RNA motifs remains challenging due to the substantial length of lncRNA transcripts and the rapid evolutionary turnover of lncRNA sequences. Nevertheless, the recent discovery of specific RNA elements, together with their experimental interrogation, has enabled the first step in classifying heterogeneous lncRNAs into sub-groups with similar molecular mechanisms and functions. In this Review, we focus on lncRNAs with roles in development, cell differentiation and normal physiology in vertebrates, and we discuss the sequence elements defining their functions. We also summarize progress on the discovery of regulatory RNA sequence elements, as well as their molecular functions and interaction partners.
... BMP/OP-responsive gene (BORG) in a C2C12 mouse myoblast cell line which trans-differentiates into osteoblastic cells reacts to bone morphogenetic proteins (BMPs) (83), particularly alters the proliferation of disseminated BC cells. ...
Breast cancer (BC) remains the most frequently diagnosed cancer worldwide. Among breast cancer patients, distant metastasis and invasion is the leading cause of BC related death. Recently, long non-coding RNAs (lncRNAs), which used to be considered a genetic byproduct (owing to their unknown biological function), have been reported to be highly implicated in the development and progression of BC. In this review, we produce a summary of the functions and mechanisms of lncRNAs implicated in the different distant metastases of BC. The functions of lncRNAs have been divided into two types: oncogenic type and tumor suppressor. Furthermore, the majority of them exert their roles through the regulation of invasion, migration, epithelial—mesenchymal transition (EMT), and the metastasis process. In the final part, we briefly addressed future research prospects of lncRNAs, especially the testing methods through which to detect lncRNAs in the clinical work, and introduced several different tools with which to detect lncRNAs more conveniently. Although lncRNA research is still in the initial stages, it is a promising prognosticator and a novel therapeutic target for BC metastasis, which requires more research in the future.
... Although numerous lncRNAs have been linked to breast cancer tumorigenesis and metastasis [49] , the intergenic lncRNA BORG has recently emerged as a unique and formidable regulator of the metastatic competence and survival of breast cancer cells. Originally discovered in murine C2C12 myoblast cells treated with BMP2 or BMP7, BORG is a spliced and polyadenylated ~2.8 kb transcript that shows no evidence of an open reading frame and carries multiple conserved repeat sequence elements of unclear significance [50] . Collectively, these features implicate BORG as a lncRNA, whose primary sequence has been subject to several functional analyses. ...
... Tumor progression and metastatic competence are thought to rely heavily upon the intrinsic plasticity of malignant cells, which facilitates their adaptation to harsh foreign microenvironments in order to maintain viability [67,107] . Because BORG is largely regulated by extracellular paracrine factors (e.g., TGF-b, BMP-2, and BMP-7 [50,56] ) and the environmental cues, we surmise that BORG acts as a context-dependent, transcriptional rheostat for disseminated breast cancer cells, thereby dictating their engagement of proliferative and prosurvival pathways. Indeed, when faced with environmental or therapeutic stresses, the induction of BORG in malignant cells orchestrates a transcriptional signature that provokes aggressive tumorigenic states that ensures for their survival. ...
Although greater than 90% of breast cancer-related mortality can be attributed to metastases, the molecular mechanisms underpinning the dissemination of primary breast tumor cells and their ability to establish malignant lesions in distant tissues remain incompletely understood. Genomic and transcriptomic analyses identified a class of transcripts called long noncoding RNA (lncRNA), which interact both directly and indirectly with key components of gene regulatory networks to alter cell proliferation, invasion, and metastasis. We identified a pro-metastatic lncRNA BMP/OP-Responsive Gene (BORG) whose aberrant expression promotes metastatic relapse by reactivating proliferative programs in dormant disseminated tumor cells (DTCs). BORG expression is broadly and strongly induced by environmental and chemotherapeutic stresses, a transcriptional response that facilitates the survival of DTCs. Transcriptomic reprogramming in response to BORG resulted in robust signaling via survival and viability pathways, as well as decreased activation of cell death pathways. As such, BORG expression acts as a (1) marker capable of predicting which breast cancer patients are predisposed to develop secondary metastatic lesions; and (2) unique therapeutic target to maximize chemosensitivity of DTCs. Here we review the molecular and cellular factors that contribute to the pathophysiological activities of BORG during its regulation of breast cancer metastasis, chemoresistance, and disease recurrence.
... Long noncoding RNAs (lncRNAs) are defined as transcripts longer than 200 nucleotides and were originally regarded as transcriptional "noise" [11,12]. In recent years, many studies have reported that lncRNAs are involved in cell osteogenic differentiation, such as lncRNA BORG [13], lncRNA ANCR [14], and lncRNA DANCR [15]. Our previous microarray data revealed that numerous lncRNAs exhibit significant expression differences after irradiation. ...
... LncRNA plays an important role in regulating the osteogenic differentiation of BM-MSCs [13][14][15]. Thousands of lncRNAs are differentially expressed in BM-MSCs under normal in vitro osteogenic induction [30]. Several important lncRNAs of BM-MSC osteogenesis, including lncRNA-H19 [31,32], and lncRNA-ANCR [14], had been found. ...
Irradiation can greatly inhibit osteogenesis of bone marrow mesenchymal stem cells (BM-MSCs). However, the mechanism remains unclear.
Methods: We analyzed the expression profile of long noncoding RNAs (lncRNAs) in BM-MSCs using microarray data. LncRNA TUG1 (Taurine Upregulated Gene 1) was selected and tested in radiated BM-MSCs and non-radiated BM-MSCs. Functional analyses (in vitro) were performed to confirm the role of TUG1 in the osteogenic inhibition induced by irradiation. A RIP (RNA immunoprecipitation) assay was performed to detect the interaction of TUG1 and Smad5. Smad5 and the phosphorylated Smad5 (p-Smad5) were tested by western blot. The nuclear translocation of p-Smad5 were tested by immunofluorescence analysis. Furthermore, a series of Smad5 deletions was constructed to identify the TUG1 binding site of Smad5.
Results: We found that numerous lncRNAs, including TUG1, exhibit significant expression differences after irradiation. After irradiation TUG1 was significantly increased in BM-MSCs and inhibited osteogenesis. Furthermore, TUG1 directly bound to Smad5, an osteogenic enhancer. Although the phosphorylation level of Smad5 was increased following irradiation, osteogenesis of BM-MSCs was decreased. Mechanistically, TUG1 interacting with the 50-90 aa region of Smad5 and blocks the nuclear translocation of p-Smad5, abolishing osteogenic signalling after irradiation.
Conclusion: These results indicate that TUG1 is a negative regulator of Smad5 signalling and suppresses osteogenesis of BM-MSCs after irradiation.
... The expression of lncRNAs is robustly regulated by conditions that challenge the viability of breast cancer cells undergoing the process of metastasis (e.g., hypoxia and metabolic stress; [27]). Furthermore, we [24,28] and others [29] demonstrated that BORG expression is robustly induced in cells exposed to stress-associated cytokines. These findings, together with our recent study identifying BORG as a novel driver of metastatic progression [24], led us to surmise that upregulated BORG expression may function as a master regulator of cell survival signaling activated in response to cellular stressors experienced by breast cancer cells as they traverse the metastatic cascade. ...
... g Scatter plot depicting quantification and correlation of internally normalized expression of BORG and hallmark NF-κB-associated transcripts in 18 RNA-seq datasets (16 derived from normal or malignant mammary tissues, 1 derived from airway epithelial cells, 1 derived from osteosarcoma cells) BORG expression in TNBCs remain to be fully elucidated. Although BORG expression is responsive to cytokine administration and microenvironmental composition [24,28,29], no unifying regulatory pathway capable of reliably controlling the transcriptional regulation of BORG has emerged. Curiously, the promoter region of BORG harbors multiple motifs containing high sequence homology for the p50/p65 NF-κB consensus DNA-binding sequence (Supplementary Fig. 4a), thereby implicating NF-κB as a potential inducer of BORG expression. ...
Disseminated breast cancer cells employ adaptive molecular responses following cytotoxic therapeutic insult which promotes their survival and subsequent outgrowth. Here we demonstrate that expression of the pro-metastatic lncRNA BORG (BMP/OP-Responsive Gene) is greatly induced within triple-negative breast cancer (TNBC) cells subjected to environmental and chemotherapeutic stresses commonly faced by TNBC cells throughout the metastatic cascade. This stress-mediated induction of BORG expression fosters the survival of TNBC cells and renders them resistant to the cytotoxic effects of doxorubicin both in vitro and in vivo. The chemoresistant traits of BORG depend upon its robust activation of the NF-κB signaling axis via a novel BORG-mediated feed-forward signaling loop, and via its ability to bind and activate RPA1. Indeed, genetic and pharmacologic inhibition of NF-κB signaling or the DNA-binding activity of RPA1 abrogates the pro-survival features of BORG and renders BORG-expressing TNBCs sensitive to doxorubicin-induced cytotoxicity. These findings suggest that therapeutic targeting of BORG or its downstream molecular effectors may provide a novel means to alleviate TNBC recurrence.
... In addition, accumulating evidence indicates that lncRNAs regulate gene expression through their interactions with DNAs, RNAs and proteins (6). Recent studies have also demonstrated that numerous lncRNAs are involved in the regulation of osteogenic differentiation of MSCs (7)(8)(9). However, the potential functions and regulatory mechanisms of lncRNAs that are associated with the osteogenic differentiation of hBMSCs remain to be elucidated. ...
Long non‑coding RNAs (lncRNAs) are a specific group of RNA molecules that do not encode proteins. They have been shown to serve important regulatory functions in various biological and cell differentiation processes. However, the potential functions and regulatory mechanisms of lncRNAs that are associated with the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) remain to be elucidated. The present study aimed to investigate lncRNAs that are differentially expressed during the osteogenic differentiation of hBMSCs, along with the potential functions of those lncRNAs. To this end, three groups of hBMSCs were stimulated to undergo osteogenic differentiation for 7 days. Known lncRNAs, unknown lncRNAs and mRNAs that demonstrated differential expression prior to and following the osteogenic differentiation of hBMSCs were screened using lncRNA high‑throughput sequencing. In addition, 12 lncRNAs were selected for reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) validation of the accuracy of the sequencing results. The potential functions and possible targets of the differentially expressed lncRNAs were analyzed using bioinformatics technologies (gene ontology, Kyoto Encyclopedia of Genes and Genomes and gene co‑expression network analysis). In total, 64 lncRNAs were differentially expressed by at least two‑fold in hBMSCs prior to and following osteogenic differentiation; these included seven known lncRNAs (two upregulated and five downregulated lncRNAs) and 57 unknown lncRNAs (35 upregulated and 22 downregulated lncRNAs). In addition, 409 mRNAs (257 upregulated and 152 downregulated mRNAs) were differentially expressed by at least two‑fold. The RT‑qPCR results obtained for 12 selected differentially expressed lncRNAs were consistent with the sequencing results. The gene co‑expression network analysis of lncRNAs and mRNAs demonstrated that four lncRNAs (ENSG00000238042, lnc_1269, lnc_1369 and lnc_1708) may serve important roles in the osteogenic differentiation of hBMSCs. In conclusion, during the osteogenic differentiation of hBMSCs, the lncRNA expression profile changed significantly; certain of the observed differentially expressed lncRNAs may be derived from protein‑coding genes and may serve important roles in osteogenic differentiation.
... Furthermore, 3ʹUTRs can be separately expressed and convey genetic functions in trans 71 , and may be further processed to produce subsidiary species 72 . lncRNAs are expressed in stem cells 73 , muscles 74 , T cells 75 , mammary gland 76 , and neurons 77 , as well as in malignant neoplasms and other diseases 76,[78][79][80] . This expression it seems to be partly controlled by conventional transcription factors 64,81 . ...
Epigenetics, present a new discipline that attempts to explain significant differences in phenotypes among patients with the same disease. In contrast to the other epigenetic mechanisms that modulate gene transcription, non-coding RNAs act at the post-transcriptional level. They directly modulate the gene expression of mRNA genes leading to mRNA target cleavage and degradation and translation repression. Bioinformatic predictions indicate that non coding RNAs may be involved in the regulation of 60% of the coding genes and each non-coding RNA can have multiple target genes, and each gene may be regulated by more than one non-coding RNAs. In the last decade several studies have shown a significant role of non-coding RNAs in the regulation of bone metabolism and function of bone cells opening a new era in the understanding of bone biology in health and disease.
... Included amongst the 17 differentially expressed lncRNAs identified via this method was BORG, which is an intergenic lncRNA approximately 2.8 kb in length that is essential in driving cell survival in response to a wide variety of cellular stress insults (e.g., heat shock, hypoxia, and nutrient deprivation 14 ;Valadkhan et al.,unpublished data). Disseminated tumor cells also face immense metabolic, oxidative, and physical stresses during transit to and within the metastatic microenvironment. ...
... Historically, the functions of BORG have been discerned in various murine cell-based systems (e.g., myoblasts, bone marrow stromal cells, mammary epithelial cells) 14,24 , which prompted us to initially investigate the potential associations of BORG with breast cancer development and metastasis across several murine breast cancer models. In doing so, we quantified BORG expression across the murine 4T1 progression series 25 , which is a model of TNBC comprised of the nonmalignant 67NR, systemically invasive but non-metastatic 4T07, and the highly metastatic 4T1 cell lines. ...
... D2.HAN cells were engineered to stably express firefly luciferase by transfection with pNifty-CMV-luciferase, followed by zeocin selection (500 μg/ml; Invitrogen) as described 33 . The full-length BORG transcript and mutant BORG deletions were created as described 14 and used to transfect D2.OR cells, followed by selection with G418 (500 μg/ ml) to generate stable cell lines. Similarly, doxycycline-controlled expression of BORG was generated via VSVG lentiviral co-transduction of D2.OR cells with M2-rTTA vector and vectors expressing BORG under control of the Tet-Response Element (pLVX-tight-puro). ...
Long noncoding RNAs (lncRNAs) have emerged as potent regulators of breast cancer development and progression, including the metastatic spread of disease. Through in silico and biological analyses, we identified a novel lncRNA, BMP/OP-Responsive Gene (BORG), whose expression directly correlates with aggressive breast cancer phenotypes, as well as with metastatic competence and disease recurrence in multiple clinical cohorts. Mechanistically, BORG elicits the metastatic outgrowth of latent breast cancer cells by promoting the localization and transcriptional repressive activity of TRIM28, which binds BORG and induces substantial alterations in carcinoma proliferation and survival. Moreover, inhibiting BORG expression in metastatic breast cancer cells impedes their metastatic colonization of the lungs of mice, implying that BORG acts as a novel driver of the genetic and epigenetic alterations that underlie the acquisition of metastatic and recurrent phenotypes by breast cancer cells.
