Project description:The study involved transcriptome analysis using RNA-seq knockdown of BORIS/CTCFL gene expression in K652 cancer cell line using inducible shRNA. The K562 cell line is the only cancer cell line that is known to be dependent on BORIS for proliferation and self-renewal of stemness. The goal of the study was to investigate the early/immediate transcriptional response to BORIS downregulation (over 10-fold reduction in protein level) using an inducible shRNA.
Project description:The study involved transcriptome analysis using RNA-seq knockdown of BORIS/CTCFL gene expression in K652 cancer cell line using inducible shRNA. The K562 cell line is the only cancer cell line that is known to be dependent on BORIS for proliferation and self-renewal of stemness. The goal of the study was to investigate the early/immediate small RNA transcriptional response to BORIS downregulation (over 10-fold reduction in protein level) using an inducible shRNA.
Project description:A common aberration in cancer is the activation of germline-specific proteins. The DNA-binding proteins among them generate novel chromatin states, not found in normal cells. The chromatin architecture protein CTCF has a germline-specific paralog BORIS/CTCFL, which is often erroneously activated in cancers. Another common feature of malignancies is the changed expression and epigenetic states of genomic repeats. The investigation of BORIS and CTCF binding to DNA repeats in cancer cell lines by ChIP-chip revealed three classes: elements cohabited by BORIS and CTCF, CTCF-bound only, or BORIS-only.
Project description:Melanoma is the deadliest form of skin cancer, due to its tendency to metastasize early. Brother of Regulator of Imprinted Sites (BORIS), also known as CCCTC binding factor-Like (CTCFL), is a transcription regulator that becomes ectopically expressed in melanoma. We recently showed that BORIS contributes to melanoma phenotype switching by altering the gene expression program of proliferative melanoma cells in favor of a more invasive phenotype. However, how BORIS alters the transcriptome remains unclear. Here, ATAC-seq was used to study BORIS-mediated chromatin accessibility alterations in proliferative melanoma cells. Genes that gained promoter accessibility following ectopic BORIS expression, were enriched for melanoma-specific invasive genes as well as invasion-associated biological processes, while promoters of genes associated with proliferation show reduce accessibility. Integration of ATAC-Seq and RNA-Seq data demonstrates that increased chromatin accessibility is associated with transcriptional upregulation of genes involved in tumor progression processes, and the aberrant activation of oncogenic transcription factors, while reduced chromatin accessibility and downregulated genes, were associated with repressed activity of tumor suppressors. Together, these findings indicate that BORIS mediates transcriptional reprogramming in melanoma cells by altering chromatin accessibility and gene expression, shifting the cellular transcription landscape of proliferative melanoma cells towards a pro-invasive genetic signature.
Project description:The identification of prognostic biomarkers is a priority for patients suffering from high-grade serous ovarian cancer (SOC), which accounts for >70% of ovarian cancer (OC) deaths. Meanwhile borderline ovarian cancer (BOC) is a low malignancy tumor and usually patients undergo surgery with low probabilities of recurrence. However, SOC remains the most lethal neoplasm due to the lack of biomarkers for early diagnosis and prognosis. In this regard BORIS (CTCFL), a CTCF paralog, is a promising cancer biomarker that is overexpressed and controls transcription in several cancer types, mainly in OC. Studies suggest that BORIS has an important function in OC by altering gene expression, but the effect and extent to which BORIS influences transcription in OC from a genome-wide perspective is unclear. Here we sought to identify BORIS target genes in an OC cell line (OVCAR3) with potential biomarker use in OC tumor samples. To achieve this, we performed in vitro knockout (KO) and knockdown (KD) experiments of BORIS in OVCAR3 cell line followed by expression microarrays and bioinformatics network enrichment analysis to identify relevant BORIS target genes.
Project description:CTCF and BORIS (CTCFL), two paralogous mammalian proteins sharing nearly identical DNA binding domains, are thought to function in mutually exclusive manners in DNA binding and transcriptional regulation. Here we show that these two proteins co-occupy a specific subset of regulatory elements consisting of clustered CTCF binding motifs (termed 2xCTSes). BORIS occupancy at 2xCTSes is largely invariant in BORIS-positive cancer cells, with the genomic pattern recapitulating the germline-specific BORIS binding to chromatin. In contrast to the single-motif CTCF target sites (1xCTSes), the 2xCTS elements are preferentially found at active promoters and enhancers, both in cancer and germ cells. 2xCTSes are also enriched in genomic regions that escape histone to protamine replacement in human and mouse sperm. Depletion of BORIS gene leads to altered transcription of a large number of genes and the differentiation of K562 cells, while the ectopic expression of this CTCF paralog leads to specific changes in transcription in MCF7 cells. In summary, we discover two functionally and structurally different classes of CTCF binding regions, 2xCTSes and 1xCTSes, revealed by their predisposition to bind BORIS. We propose that 2xCTSes play key roles in the transcriptional program of cancer and germ cells Genome-wide mapping of CTCF and BORIS occupancies in both germ and cancer cells. ChIP-seq and expression profiling by high throughput sequencing
Project description:Ctcfl, a paralog of Ctcf, also known as BORIS (Brother of Regulator of Imprinted Sites), is a testis expressed gene whose function is largely unknown. As a cancer testis antigen, it is often expressed in tumor cells and also seen in two benign human vascular malformations, juvenile angiofibromas (JA) and infantile hemangiomas (IH). To better understand the function of Ctcfl we created tetracycline-inducible Ctcfl transgenic mice. We show that when Ctcfl expression is induced during embryogenesis, it results in intrauterine growth retardation, developmental eye malformations, multi-organ pathologies, vascular defects, and early neonatal lethality. This phenotype resembles prior mouse models which perturb the TGFB pathway. Embryonic stem cells with the Ctcfl transgene reproduce the same phenotype in ES cell: tetraploid chimeras. RNA-Seq of the Ctcfl ES cells revealed 14 genes, including a number of transcription factors/ co-activators, and signal transduction pathway genes that are significantly deregulated by Ctcfl expression. Bioinformatics analysis revealed the TGFB pathway to be most affected by embryonic Ctcfl expression. We propose that our transgenic mice reiterate a developmental program normally reserved for spermatogenesis that results in multiple organ pathology when expressed in embryogenesis as a result of the TGFB pathway dysregulation. Understanding of the phenotypic consequence of Ctcfl expression in non-testicular cells and elucidating downstream targets of Ctcfl has the potential to explain its role as a cancer testis antigen (CTA) and its involvement in two, if not more, human vascular malformations.
Project description:Brother of Regulator of Imprinted Sites (BORIS) is a DNA binding protein with high similarity to CCCTC binding factor (CTCF), a multifunctional transcription factor that plays an important role in genome organization. Like CTCF, BORIS plays a role in transcriptional regulation. BORIS becomes aberrantly expressed in melanoma with a higher frequency in metastatic tumors compared to primary tumors, which indicates a role for BORIS in melanoma progression. Currently, little is known about the role of BORIS in melanoma. To gain insight into the functional role of BORIS in melanoma we established doxycycline-inducible BORIS expression in the MM057 melanoma cell line that harbors a proliferation-associated transcriptome. Next, we used RNA-seq to investigate BORIS-mediated transcriptional changes. We show that differentially expressed genes are enriched among invasion-related processes and gene signatures, indicating that BORIS expression contributes to an EMT-like switch from a proliferation to invasion-associated transcriptome. In agreement with these findings, we demonstrate that BORIS overexpression leads to reduced proliferation and increased migration and invasion. Taken together, these data indicate that expression of BORIS promotes a switch from a proliferative to invasive state at both the transcriptional and phenotypic level in melanoma cell lines.
Project description:Pervasive usage of alternative promoters leads to deregulation of gene expression in carcinogenesis and may drive the emergence of new genes in spermatogenesis. However, little is known regarding the mechanisms underpinning the activation of alternative promoters. In our present study, we uncovered a novel mechanism by which alternative cancer-testis-specific transcription is activated from the intergenic and intronic clustered CTCF binding sites, which are transcriptionally inert in normal somatic cells. BORIS/CTCFL, a paralog of CTCF with cancer-testis-specific expression forms a heterodimer with CTCF at the clustered binding sites thus triggering epigenetic reprogramming of these sites into units of active transcription. BORIS binding to CTCF sites leads to the recruitment of chromatin-remodeling factor SRCAP, with subsequent replacement of H2A histone with H2A.Z, therefore creating a more relaxed chromatin state in the nucleosomes flanking the clustered binding sites. This facilitates opening of chromatin beyond CTCF/BORIS binding sites and paves the way to the recruitment of multiple additional transcription factors, thereby activating transcription from a given binding site. We demonstrate that the CTCF binding sites, epigenetically reprogrammed by ectopic BORIS expression can drive the expression of cancer-testis genes, long-noncoding RNAs, retro-pseudogenes, and dormant transposable elements harbored by activated long transcripts. Taking together, our results reveal that BORIS functions as a transcription factor that epigenetically reprograms clustered CTCF binding sites into transcriptional start sites, promoting transcription from alternative promoters in both germ cells and cancer cells.
Project description:High-grade serous carcinoma (HGSC) is the most aggressive and predominant form of epithelial ovarian cancer and the leading cause of gynecological cancer death. We have previously shown that CTCFL (also known as BORIS, Brother of the Regulator of Imprinted Sites) is expressed in a large proportion of ovarian cancers, which is associated with global and promoter-specific DNA hypomethylation, advanced tumor stage, and poor prognosis. To explore its functional role in HGSC, we expressed BORIS in human fallopian tube secretory epithelial cells (FTSEC), the presumptive cell of origin for HGSC. BORIS-expressing cells exhibited increased motility and invasion, and BORIS expression was associated with alterations in several cancer-associated gene expression networks, including fatty acid metabolism, TNF signaling, cell migration, and ECM-receptor interactions. Importantly, GALNT14, a glycosyltransferase gene previously implicated in cancer cell migration and invasion, was highly induced by BORIS, and GALNT14 knockdown significantly abrogated BORIS-induced cell motility and invasion. In addition, in silico analyses provided evidence for BORIS and GALNT14 co-expression in several human cancers. Finally, ChIP-seq demonstrated that expression of BORIS in FTSEC cells was associated with de novo and enhanced binding of CTCF at hundreds of loci, many of which correlated with activation of transcription at target genes, including GALNT14. Taken together, our data indicate that BORIS may promote cell motility and invasion in HGSC via upregulation of GALNT14, and suggests BORIS as a potential therapeutic target in this malignancy.