Tumor Suppressor Candidate Region Gene Research Articles

GLTSCR1 coordinates alternative splicing and transcription elongation of ZO1 to regulate colorectal cancer progression.

Alternative splicing (AS) and transcription elongation are vital biological processes, and their dysregulation causes multiple diseases, including tumors. However, the coregulatory mechanism of AS and transcription elongation in tumors remains unclear. This study demonstrates a novel AS pattern of tight junction protein 1 (ZO1) regulated by the RNA polymerase II elongation rate in colorectal cancer (CRC). Glioma tumor suppressor candidate region gene 1 (GLTSCR1) decreases the transcription elongation rate of ZO1 to provide a time window for binding of the splicing factor HuR to the specific motif in intron 22 of ZO1 and spliceosome recognition of the weak 3′ and 5′ splice sites in exon 23 to promote exon 23 inclusion. Since exon 23 inclusion in ZO1 suppresses migration and invasion of CRC cells, our findings suggest a novel potential therapeutic target for CRC.

GLTSCR1 Negatively Regulates BRD4-Dependent Transcription Elongation and Inhibits CRC Metastasis.

Frameshift mutations frequently occur in colorectal cancer (CRC) with microsatellite instability (MSI), but the nature and biological function of many MSI‐associated mutations remain elusive. Here, an MSI frameshift mutation is identified in glioma tumor suppressor candidate region gene 1 (GLTSCR1) that produces two C‐terminal‐truncated proteins. Additionally, GLTSCR1 is verified as a tumor suppressor that inhibits CRC metastasis. Through binding to bromodomains and the phosphorylation‐dependent interaction domain of bromodomain protein 4 (BRD4) via the C‐terminus, GLTSCR1 blocks oncogenic transcriptional elongation. However, truncated GLTSCR1 translocates into the cytoplasm and loses BRD4 binding domain, which induces the phosphorylation of RNA Pol II at Ser2 and dephosphorylation at Ser5, then increases oncogenic transcriptional elongation. Importantly, GLTSCR1 deficiency decreases sensitivity to bromodomain and extra terminal domain inhibitors. This study highlights the molecular mechanism of the GLTSCR1‐BRD4 interaction, which is a potential therapeutic target for CRC.

A non-canonical BRD9-containing BAF chromatin remodeling complex regulates naive pluripotency in mouse embryonic stem cells

The role of individual subunits in the targeting and function of the mammalian BRG1-associated factors (BAF) complex in embryonic stem cell (ESC) pluripotency maintenance has not yet been elucidated. Here we find that the Bromodomain containing protein 9 (BRD9) and Glioma tumor suppressor candidate region gene 1 (GLTSCR1) or its paralog GLTSCR1-like (GLTSCR1L) define a smaller, non-canonical BAF complex (GBAF complex) in mouse ESCs that is distinct from the canonical ESC BAF complex (esBAF). GBAF and esBAF complexes are targeted to different genomic features, with GBAF co-localizing with key regulators of naive pluripotency, which is consistent with its specific function in maintaining naive pluripotency gene expression. BRD9 interacts with BRD4 in a bromodomain-dependent fashion, which leads to the recruitment of GBAF complexes to chromatin, explaining the functional similarity between these epigenetic regulators. Together, our results highlight the biological importance of BAF complex heterogeneity in maintaining the transcriptional network of pluripotency.

High levels of glioma tumor suppressor candidate region gene 1 predicts a poor prognosis for prostate cancer.

Glioma tumor suppressor candidate region gene 1 (GLTSCR1) is associated with the progression of oligodendroglioma. However, there has been little study of GLTSCR1 in prostate cancer. In the present study, the association between the expression of GLTSCR1, and the progression and prognosis of tumors in patients with prostate cancer was assessed. An immunohistochemical analysis was performed using a human tissue microarray for GLTSCR1 at the protein expression level and the immunostaining results were evaluated against clinical variables of patients with prostate cancer. Subsequently, The Cancer Genome Atlas (TCGA) was used to validate the analysis results at the mRNA level and to study the prognostic value of GLTSCR1 in prostate cancer. Immunohistochemistry and TCGA data analysis revealed that GLTSCR1 expression in the prostate cancer tissues was significantly higher than that in the benign prostate tissues (immunoreactivity score, P=0.015; mRNA levels: cancer, 447.7±6.45 vs. benign, 343.5±4.21; P<0.001). Additionally, the increased GLTSCR1 protein expression was associated with certain clinical variables in the prostate cancer tissues, including advanced clinical stage (P<0.001), enhanced tumor invasion (P=0.003), lymph node metastasis (P=0.003) and distant metastasis (P=0.001). TCGA data revealed similar results, demonstrating that the upregulation of GLTSCR1 mRNA expression was associated with the Gleason score (P<0.001), enhanced tumor invasion (P=0.011), lymph node metastasis (P=0.001) and distant metastasis (P=0.002). Furthermore, Kaplan-Meier analysis suggested that among all patients, high GLTSCR1 expression indicated a decreased overall survival (P=0.028) and biochemical recurrence (BCR)-free survival (P=0.004), compared with patients with low GLTSCR1 expression. Finally, multivariate analysis revealed that the expression of GLTSCR1 was an independent predictor of poor BCR-free survival (P=0.049). The present study suggested that the increased expression of GLTSCR1 was associated with the progression of prostate cancer. Furthermore, GLTSCR1 may be a novel biomarker that is able to predict the clinical outcome in prostate cancer patients.

GLTSCR1, ATM, PPP1R13L and CD3EAP Genetic Variants and Lung Cancer Risk in a Chinese Population.

Genetic variants in glioma tumor suppressor candidate region gene 1 (GLTSCR1) and ATM serine/threonine kinase (ATM) have been associated with various cancer risks. Epidemiological studies also revealed the association of variants of GLTSCR1 and ATM genes with different brain tumors. However, little is known about the relationship between both gene polymorphisms and lung cancer risk. We conducted a Chinese hospital-based casecontrol study involving 384 lung cancer cases and 387 cancer-free controls. No significant differences in the single polymorphism (GLTSCR1 rs1035938 and ATM rs11212592) association were found in five genetic models (co-dominant, dominant, recessive, overdominant and log-additive models) (adjusted by smoking duration). Join effect of three SNPs (PPP1R13L rs1970764, CD3EAP rs967591, GLTSCR1 rs1035938) on chromosome 19q13.3 showed that the designated haplotype8 (rs 1970764G-rs967591A-rs1035938C) [OR (95% CI)=1.60(1.11-2.32), P/0.012] andhaplotype8 (rs1970764G-rs967591G-rs1035938T) [OR (95% CI)=2.45 (1.17-5.12), P=0.018] were associated with increased risk of lung cancer (adjusted by smoking duration). The analysis of multifactor dimensionality reduction revealed that two 3-way models were the best fit models in analyses of 2 loci (P<0.001) or 4 loci (Р=0.015-0.016). The entropy-based analysis indicated the strongest synergistic effect between PPP1R13L rs1970764 and ATM rs11212592 in analysis of four genes. In conclusion, our study suggests that haplotypes consisting of PPP1R13L rs1970764-CD3EAP rs961591-GLTSCR1 rs1035938 on Chr19q13.3, interaction of smoking and GLTSCR1 rs1035938-ATM rs11212592, and synergistic action of PPP1R13L rs1970764 and ATM rs11212592 may associate with lung cancer risk in the Chinese population.

Glioma tumor suppressor candidate region gene 1 (GLTSCR1) and its paralog GLTSCR1-like form SWI/SNF chromatin remodeling subcomplexes

The mammalian SWI/SNF chromatin remodeling complex is a heterogeneous collection of related protein complexes required for gene regulation and genome integrity. It contains a central ATPase (BRM or BRG1) and various combinations of 10-14 accessory subunits (BAFs for BRM/BRG1 Associated Factors). Two distinct complexes differing in size, BAF and the slightly larger polybromo-BAF (PBAF), share many of the same core subunits but are differentiated primarily by having either AT-rich interaction domain 1A/B (ARID1A/B in BAF) or ARID2 (in PBAF). Using density gradient centrifugation and immunoprecipitation, we have identified and characterized a third and smaller SWI/SNF subcomplex. We termed this complex GBAF because it incorporates two mutually exclusive paralogs, GLTSCR1 (glioma tumor suppressor candidate region gene 1) or GLTSCR1L (GLTSCR1-like), instead of an ARID protein. In addition to GLTSCR1 or GLTSCR1L, the GBAF complex contains BRD9 (bromodomain-containing 9) and the BAF subunits BAF155, BAF60, SS18, BAF53a, and BRG1/BRM. We observed that GBAF does not contain the core BAF subunits BAF45, BAF47, or BAF57. Even without these subunits, GBAF displayed in vitro ATPase activity and bulk chromatin affinity comparable to those of BAF. GBAF associated with BRD4, but, unlike BRD4, the GBAF component GLTSCR1 was not required for the viability of the LNCaP prostate cancer cell line. In contrast, GLTSCR1 or GLTSCR1L knockouts in the metastatic prostate cancer cell line PC3 resulted in a loss in proliferation and colony-forming ability. Taken together, our results provide evidence for a compositionally novel SWI/SNF subcomplex with cell type-specific functions.

The nucleolar protein GLTSCR2 is required for efficient viral replication.

Glioma tumor suppressor candidate region gene 2 protein (GLTSCR2) is a nucleolar protein. In the investigation of the role of GLTSCR2 that played in the cellular innate immune response to viral infection, we found GLTSCR2 supported viral replication of rhabdovirus, paramyxovirus, and coronavirus in cells. Viral infection induced translocation of GLTSCR2 from nucleus to cytoplasm that enabled GLTSCR2 to attenuate type I interferon IFN-β and support viral replication. Cytoplasmic GLTSCR2 was able to interact with retinoic acid-inducible gene I (RIG-I) and the ubiquitin-specific protease 15 (USP15), and the triple interaction induced USP15 activity to remove K63-linked ubiquitination of RIG-I, leading to attenuation of RIG-I and IFN-β. Blocking cytoplasmic translocation of GLTSCR2, by deletion of its nuclear export sequence (NES), abrogated its ability to attenuate IFN-β and support viral replication. GLTSCR2-mediated attenuation of RIG-I and IFN-β led to alleviation of host cell innate immune response to viral infection. Our findings suggested that GLTSCR2 contributed to efficient viral replication, and GLTSCR2 should be considered as a potential target for therapeutic control of viral infection.

Role of GLTSCR2 in the regulation of telomerase activity and chromosome stability.

Telomerase is essential for regulating telomeres, and its activation is a critical step in cellular immortalization and tumorigenesis. The transcriptional activation of human telomerase reverse transcriptase (hTERT) is critical for telomerase expression. Although several transcriptional activators have been identified, factors responsible for enhancing the hTERT promoter remain to be fully elucidated. In the present study, the role of glioma tumor-suppressor candidate region gene2 (GLTSCR2) in telomerase regulation was analyzed. A doxycyclin-inducible green fluorescent protein (GFP)-tagged GLTSCR2-expressing adenovirus (Ad‑GLT/GFP) was used for the transduction of SK‑Hep‑1 and T98G cancer cells, and normal human umbilical vein endothelial cells. Changes in telomerase activity using telomere repeat amplification protocol assay were assessed, and the gene expression levels of hTERT were then examined. To investigate chromosome instability and senescence, Giemsa and β-galactosidase staining was performed. The results revealed that overexpression of GLTSCR2 significantly increased telomerase activity in the cancer and normal cell lines. This increase was consistent with increases in the protein and mRNA expression levels of hTERT. In luciferase assays, the hTERT promoter was activated by GLTSCR2. Knockdown of GLTSCR2 led to the downregulation of telomerase activity, abnormal nuclear morphology as a marker of chromosome instability, significant suppression of growth rate, alterations in cellular morphology and, eventually, cellular senescence. Taken together, the results of the present study suggested that GLTSCR2 is crucially involved in the positive regulation of telomerase and chromosome stability.

Gene expression analysis in MCF-7 breast cancer cells treated with recombinant bromelain.

The contributing molecular pathways underlying the pathogenesis of breast cancer need to be better characterized. The principle of our study was to better understand the genetic mechanism of oncogenesis for human breast cancer and to discover new possible tumor markers for use in clinical practice. We used complimentary DNA (cDNA) microarrays to compare gene expression profiles of treated Michigan Cancer Foundation-7 (MCF-7) with recombinant bromelain and untreated MCF-7. SpringGene analysis was carried out of differential expression followed by Ingenuity Pathway Analysis (IPA), to understand the underlying consequence in developing disease and disorders. We identified 1,102 known genes differentially expressed to a significant degree (p<0.001) changed between the treatment. Within this gene set, 20 genes were significantly changed between treated cells and the control cells with cutoff fold change of more than 1.5. These genes are RNA-binding motif, single-stranded interacting protein 1 (RBMS1), ribosomal protein L29 (RPL29), glutathione S-transferase mu 2 (GSTM2), C15orf32, Akt3, B cell translocation gene 1 (BTG1), C6orf62, C7orf60, kinesin-associated protein 3 (KIFAP3), FBXO11, AT-rich interactive domain 4A (ARID4A), COPS2, TBPL1|SLC2A12, TMEM59, SNORD46, glioma tumor suppressor candidate region gene 2 (GLTSCR2), and LRRFIP. Our observation on gene expression indicated that recombinant bromelain produces a unique signature affecting different pathways, specific for each congener. The microarray results give a molecular mechanistic insight and functional effects, following recombinant bromelain treatment. The extent of changes in genes is related to and involved significantly in gap junction signaling, amyloid processing, cell cycle regulation by BTG family proteins, and breast cancer regulation by stathmin1 that play major roles.

GLTSCR2/PICT1 links mitochondrial stress and Myc signaling

Mitochondrial defects underlie a multitude of human diseases. Genetic manipulation of mitochondrial regulatory pathways represents a potential therapeutic approach. We have carried out a high-throughput overexpression screen for genes that affect mitochondrial abundance or activity using flow-cytometry-based enrichment of a cell population expressing a high-complexity, concentration-normalized pool of human ORFs. The screen identified 94 candidate mitochondrial regulators including the nuclear protein GLTSCR2, also known as PICT1. GLTSCR2 enhances mitochondrial function and is required for the maintenance of oxygen consumption, consistent with a pivotal role in the control of cellular respiration. RNAi inactivation of the Caenorhabditis elegans ortholog of GLTSCR2 reduces respiration in worms, indicating functional conservation across species. GLTSCR2 controls cellular proliferation and metabolism via the transcription factor Myc, and is induced by mitochondrial stress, suggesting it may constitute a significant component of the mitochondrial signaling pathway.

Nucleolar protein GLTSCR2 stabilizes p53 in response to ribosomal stresses

p53 is a key regulator of cell growth and death by controlling cell cycle progression and apoptosis under conditions of stress such as DNA damage or oncogenic stimulation. As these processes are critical for cell function and inhibition of tumor development, p53 regulatory pathways are strictly monitored in cells. Recently, it was recognized that nucleolar proteins, including nucleophosmin/B23, ribosomal protein L11, and alternate reading frame (ARF), form the nucleolus-ARF-murine double minute 2 (MDM2) axis in p53 regulatory pathways, which increases p53 stability by suppressing the activity of MDM2. In this work, we show that nucleolar protein glioma tumor-suppressor candidate region gene 2 (GLTSCR2) translocates to the nucleoplasm under ribosomal stress, where it interacts with and stabilizes p53 and inhibits cell cycle progression without the involvement of the major upstream p53 regulator, ARF. Furthermore, ectopic expression of GLTSCR2 significantly suppressed growth of cancer cells in a xenograft animal model via p53-dependent pathway. Our data identify GLTSCR2 as a new member of the nucleolus-nucleoplasmic axis for p53 regulation. ARF-independent direct regulation of p53 by GLTSCR2 may be a key mechanism and therapeutic target for cell death or growth inhibition when nucleolus-ARF-p53 pathways are inactivated by genetic or epigenetic modifications of ARF, which are the second most common types of genetic change observed in human cancers.

GLTSCR2 (glioma tumor suppressor candidate region gene 2)

Review on GLTSCR2 (glioma tumor suppressor candidate region gene 2), with data on DNA, on the protein encoded, and where the gene is implicated.

Non-erythroid beta spectrin interacting proteins and their effects on spectrin tetramerization

With yeast two-hybrid methods, we used a C-terminal fragment (residues 1697–2145) of non-erythroid beta spectrin (βII-C), including the region involved in the association with alpha spectrin to form tetramers, as the bait to screen a human brain cDNA library to identify proteins interacting with βII-C. We applied stringent selection steps to eliminate false positives and identified 17 proteins that interacted with βII-C (IPβII-C s). The proteins include a fragment (residues 38–284) of “THAP domain containing, apoptosis associated protein 3, isoform CRA g”, “glioma tumor suppressor candidate region gene 2” (residues 1-478), a fragment (residues 74–442) of septin 8 isoform c, a fragment (residues 704–953) of “coatomer protein complex, subunit beta 1, a fragment (residues 146–614) of zinc-finger protein 251, and a fragment (residues 284–435) of syntaxin binding protein 1. We used yeast three-hybrid system to determine the effects of these βII-C interacting proteins as well as of 7 proteins previously identified to interact with the tetramerization region of non-erythroid alpha spectrin (IPαII-N s) [1] on spectrin tetramer formation. The results showed that 3 IPβII-C s were able to bind βII-C even in the presence of αII-N, and 4 IPαII-N s were able to bind αII-N in the presence of βII-C. We also found that the syntaxin binding protein 1 fragment abolished αII-N and βII-C interaction, suggesting that this protein may inhibit or regulate non-erythroid spectrin tetramer formation.

The expression of GLTSCR2, a candidate tumor suppressor, is reduced in seborrheic keratosis compared to normal skin

Glioma tumor-suppressor candidate region gene 2 (GLTSCR2) is a recently identified nuclear protein that interacts with the tumor suppressor PTEN. GLTSCR2 regulates the stability of PTEN, and is therefore believed to have a tumor suppressive function. In a recent study, we demonstrated that GLTSCR2 often exhibits genetic alterations and down-regulation in glioblastoma specimens. However, GLTSCR2 expression levels in human tumors and its mechanism of tumor suppression remain largely unknown. We performed an immunohistochemical examination of GLTSCR2 expression in samples of seborrheic keratosis (SK, n=69), a common benign skin tumor, and normal skin ( n=23), and assessed the relationship between GLTSCR2 expression and the patients' clinicopathologic factors. Our results showed that GLTSCR2 expression in SK was significantly lower than in normal skin ( p<0.001), and this decreased expression of GLTSCR2 was associated with patient age ( p=0.045). Using in situ hybridization analysis, we found that mRNA expression of GLTSCR2 was reduced in tumor cells compared to normal skin. This is the first study analyzing the expression of GLTSCR2, a putative tumor suppressor, in SK and normal skin. Our results show a down-regulation of this protein in SK, indicating that GLTSCR2 may have a protective effect on the development of SK.

The putative tumor suppressor gene GLTSCR2 induces PTEN-modulated cell death

Glioma tumor suppressor candidate region gene 2 (GLTSCR2/PICT-1) is localized within the well-known 1.4-Mb tumor suppressive region of chromosome 19q, which is frequently altered in various human tumors, including diffuse gliomas. Aside from its localization on the chromosome, several lines of evidence, such as PTEN phosphorylation, support that GLTSCR2 partakes in the suppression of tumor growth and development. However, much remains unknown about the molecular mechanisms of the tumor suppressive activity of GLTSCR2. The purpose of this study was to investigate the molecular mechanisms of GLTSCR2 in cell death pathways in association with its binding partner PTEN. In this work, we show that GLTSCR2 is a nucleus-localized protein with a discrete globular expression pattern. In addition to phosphorylating PTEN, GLTSCR2 induces caspase-independent PTEN-modulated apoptotic cell death when overexpressed. However, the cytotoxic activity of GLTSCR2 is independent of its ability to phosphorylate PTEN, suggesting that the GLTSCR2-induced cell death pathway is divergent from PTEN-induced death pathways. Our results suggest that the induction of PTEN-modulated apoptosis is one of the putative mechanisms of tumor suppressive activity by GLTSCR2.