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Differential regulation of MAGE-A1 promoter activity by BORIS and Sp1, both interacting with the TATA binding protein.

Schwarzenbach H, Eichelser C, Steinbach B, Tadewaldt J, Pantel K, Lobanenkov V, Loukinov D - BMC Cancer (2014)

Bottom Line: Our findings show that BORIS and Sp1 have opposite effects on the regulation of MAGE-A1 gene expression.This differential regulation may be explained by direct protein-protein interaction of both factors or by interaction of MAGE-A1 promoter with BORIS alternatively spliced isoforms with different sequence specificity.We also show here that ectopic expression of BORIS can activate transcription from its own locus, inducing all its splice variants.

View Article: PubMed Central - PubMed

Affiliation: Department of Tumor Biology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, Hamburg 20246, Germany. hschwarz@uke.uni-hamburg.de.

ABSTRACT

Background: As cancer-testis MAGE-A antigens are targets for tumor immunotherapy, it is important to study the regulation of their expression in cancers. This regulation appears to be rather complex and at the moment controversial. Although it is generally accepted that MAGE-A expression is controlled by epigenetics, the exact mechanisms of that control remain poorly understood.

Methods: We analyzed the interplay of another cancer-testis gene, BORIS, and the transcription factors Ets-1 and Sp1 in the regulation of MAGE-A1 gene expression performing luciferase assays, quantitative real-time PCR, sodium bisulfite sequencing, chromatin immunoprecipitation assays and pull down experiments.

Results: We detected that ectopically expressed BORIS could activate and demethylate both endogenous and methylated reporter MAGE-A1 promoter in MCF-7 and micrometastatic BCM1 cancer cell lines. Overexpression of Ets-1 could not further upregulate the promoter activity mediated by BORIS. Surprisingly, in co-transfection experiments we observed that Sp1 partly repressed the BORIS-mediated stimulation, while addition of Ets-1 expression plasmid abrogated the Sp1 mediated repression of MAGE-A1 promoter. Both BORIS and Sp1 interacted with the TATA binding protein (hTBP) suggesting the possibility of a competitive mechanism of action between BORIS and Sp1.

Conclusions: Our findings show that BORIS and Sp1 have opposite effects on the regulation of MAGE-A1 gene expression. This differential regulation may be explained by direct protein-protein interaction of both factors or by interaction of MAGE-A1 promoter with BORIS alternatively spliced isoforms with different sequence specificity. We also show here that ectopic expression of BORIS can activate transcription from its own locus, inducing all its splice variants.

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BORIS mRNA expression in MDA-MB-468, MCF-7 and BCM1 cells,untreated or treated with 5-aza-CdR. RT-PCR products of BORIS mRNA were separated on an agarose gel.
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Fig2: BORIS mRNA expression in MDA-MB-468, MCF-7 and BCM1 cells,untreated or treated with 5-aza-CdR. RT-PCR products of BORIS mRNA were separated on an agarose gel.

Mentions: To further evaluate the stimulatory effect of BORIS on MAGE-A1 gene expression, we carried out knock-down experiments in MDA-MB-468 and MCF-7 cells. First, we determined the expression levels of BORIS in MDA-MB-468, MCF-7 and BCM1 cells by RT-PCR and gel electrophoresis. As expected, we found a similar expression profile of BORIS mRNA (Figure 2) to that detected by quantitative real-time PCR (Table 1). However, gel electrophoresis and quantitative real time showed no and low expression levels of BORIS in MCF-7 cells, respectively, but the tendency was similar. The additional stimulation with 5-aza-CdR showed that induction of BORIS expression may occur by DNA demethylation (Figure 2).


Differential regulation of MAGE-A1 promoter activity by BORIS and Sp1, both interacting with the TATA binding protein.

Schwarzenbach H, Eichelser C, Steinbach B, Tadewaldt J, Pantel K, Lobanenkov V, Loukinov D - BMC Cancer (2014)

BORIS mRNA expression in MDA-MB-468, MCF-7 and BCM1 cells,untreated or treated with 5-aza-CdR. RT-PCR products of BORIS mRNA were separated on an agarose gel.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230356&req=5

Fig2: BORIS mRNA expression in MDA-MB-468, MCF-7 and BCM1 cells,untreated or treated with 5-aza-CdR. RT-PCR products of BORIS mRNA were separated on an agarose gel.
Mentions: To further evaluate the stimulatory effect of BORIS on MAGE-A1 gene expression, we carried out knock-down experiments in MDA-MB-468 and MCF-7 cells. First, we determined the expression levels of BORIS in MDA-MB-468, MCF-7 and BCM1 cells by RT-PCR and gel electrophoresis. As expected, we found a similar expression profile of BORIS mRNA (Figure 2) to that detected by quantitative real-time PCR (Table 1). However, gel electrophoresis and quantitative real time showed no and low expression levels of BORIS in MCF-7 cells, respectively, but the tendency was similar. The additional stimulation with 5-aza-CdR showed that induction of BORIS expression may occur by DNA demethylation (Figure 2).

Bottom Line: Our findings show that BORIS and Sp1 have opposite effects on the regulation of MAGE-A1 gene expression.This differential regulation may be explained by direct protein-protein interaction of both factors or by interaction of MAGE-A1 promoter with BORIS alternatively spliced isoforms with different sequence specificity.We also show here that ectopic expression of BORIS can activate transcription from its own locus, inducing all its splice variants.

View Article: PubMed Central - PubMed

Affiliation: Department of Tumor Biology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, Hamburg 20246, Germany. hschwarz@uke.uni-hamburg.de.

ABSTRACT

Background: As cancer-testis MAGE-A antigens are targets for tumor immunotherapy, it is important to study the regulation of their expression in cancers. This regulation appears to be rather complex and at the moment controversial. Although it is generally accepted that MAGE-A expression is controlled by epigenetics, the exact mechanisms of that control remain poorly understood.

Methods: We analyzed the interplay of another cancer-testis gene, BORIS, and the transcription factors Ets-1 and Sp1 in the regulation of MAGE-A1 gene expression performing luciferase assays, quantitative real-time PCR, sodium bisulfite sequencing, chromatin immunoprecipitation assays and pull down experiments.

Results: We detected that ectopically expressed BORIS could activate and demethylate both endogenous and methylated reporter MAGE-A1 promoter in MCF-7 and micrometastatic BCM1 cancer cell lines. Overexpression of Ets-1 could not further upregulate the promoter activity mediated by BORIS. Surprisingly, in co-transfection experiments we observed that Sp1 partly repressed the BORIS-mediated stimulation, while addition of Ets-1 expression plasmid abrogated the Sp1 mediated repression of MAGE-A1 promoter. Both BORIS and Sp1 interacted with the TATA binding protein (hTBP) suggesting the possibility of a competitive mechanism of action between BORIS and Sp1.

Conclusions: Our findings show that BORIS and Sp1 have opposite effects on the regulation of MAGE-A1 gene expression. This differential regulation may be explained by direct protein-protein interaction of both factors or by interaction of MAGE-A1 promoter with BORIS alternatively spliced isoforms with different sequence specificity. We also show here that ectopic expression of BORIS can activate transcription from its own locus, inducing all its splice variants.

Show MeSH
Related in: MedlinePlus