Limits...
miR-125b-1 is repressed by histone modifications in breast cancer cell lines.

Cisneros-Soberanis F, Andonegui MA, Herrera LA - Springerplus (2016)

Bottom Line: In this work we investigated the effect of histone modifications on the regulation of this gene promoter.H3K27me3 and H3K9me3 were enriched in MCF7 and MDA-MB-231 cells, respectively.We over-expressed KDM4B/JMJD2B to reactivate this miRNA, resulting in a three-fold increase in miR-125b expression compared with the same cell line without KDM4B/JMJD2B over-expression.

View Article: PubMed Central - PubMed

Affiliation: Unidad de Investigación Biomédica en Cáncer, Instituto Nacional de Cancerología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Avenida San Fernando 22, Mexico City, 14080 Mexico.

ABSTRACT

Purpose: Downregulation of miR-125b-1 is associated with poor prognosis in breast cancer patients. In this work we investigated the effect of histone modifications on the regulation of this gene promoter.

Methods and results: We evaluated the enrichment of two histone modifications involved in gene repression, H3K9me3 and H3K27me3, on the miR-125b-1 promoter in two breast cancer cell lines, MCF7 (luminal A subtype) and MDA-MB-231 (triple-negative subtype), compared to the non-transformed breast cell line MCF10A. H3K27me3 and H3K9me3 were enriched in MCF7 and MDA-MB-231 cells, respectively. Next, we used an EZH2 inhibitor to examine the reactivation of miR-125b-1 in MCF7 cells and evaluated the transcriptional levels of pri-miR-125b-1 and mature miR-125b by qRT-PCR. pri-miRNA and mature miRNA transcripts were both increased after treatment of MCF7 cells with the EZH2 inhibitor, whereas no effect on miR-125b-1 expression levels was observed in MDA-MB-231 and MCF10A cells. We subsequently evaluated the effect of miR-125b-1 reactivation on the expression and protein levels of BAK1, a target of miR-125b. We observed 60 and 70 % decreases in the expression and protein levels of BAK1, respectively, compared to cells that were not treated with the EZH2 inhibitor. We over-expressed KDM4B/JMJD2B to reactivate this miRNA, resulting in a three-fold increase in miR-125b expression compared with the same cell line without KDM4B/JMJD2B over-expression.

Conclusion: The miR-125b-1 is repressed by different epigenetic mechanisms depending on the breast cancer subtype and that miR-125b-1 reactivation specifically eliminates the effect of repressive histone modifications on the expression of an pro-apoptotic target.

No MeSH data available.


Related in: MedlinePlus

H3K9me3 and H3K27me3 are enriched on miR-125b-1 promoters in MDA-MB-231 and MCF7 breast cancer cells, respectively. To determine which histone modification was involved in miR-125b-1 repression, we evaluated H3K9me3 (a) and H3K27me3 (b) expression in the promoter regions by chromatin immunoprecipitation
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4930440&req=5

Fig2: H3K9me3 and H3K27me3 are enriched on miR-125b-1 promoters in MDA-MB-231 and MCF7 breast cancer cells, respectively. To determine which histone modification was involved in miR-125b-1 repression, we evaluated H3K9me3 (a) and H3K27me3 (b) expression in the promoter regions by chromatin immunoprecipitation

Mentions: Two promoters are associated with miR-125b-1 transcriptional regulation. The first is in a CpG island close to the miR-125b-1 sequence (Wang et al. 2013). This CpG island has an intermediate CpG content, and thus the transcriptional regulation of miR-125b-1 may be associated with DNA methylation and histone modifications (Weber et al. 2007; Marson et al. 2008). The second promoter is 55 kb upstream from the miR-125b-1 sequence. This promoter, which may regulate the transcription of the miR-125b-1, let-7a-2 and miR-100 genes (Chien et al. 2011), is not in a CpG island, and thus the regulation of these genes may be associated with histone modifications (Fig. 2).Fig. 2


miR-125b-1 is repressed by histone modifications in breast cancer cell lines.

Cisneros-Soberanis F, Andonegui MA, Herrera LA - Springerplus (2016)

H3K9me3 and H3K27me3 are enriched on miR-125b-1 promoters in MDA-MB-231 and MCF7 breast cancer cells, respectively. To determine which histone modification was involved in miR-125b-1 repression, we evaluated H3K9me3 (a) and H3K27me3 (b) expression in the promoter regions by chromatin immunoprecipitation
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4930440&req=5

Fig2: H3K9me3 and H3K27me3 are enriched on miR-125b-1 promoters in MDA-MB-231 and MCF7 breast cancer cells, respectively. To determine which histone modification was involved in miR-125b-1 repression, we evaluated H3K9me3 (a) and H3K27me3 (b) expression in the promoter regions by chromatin immunoprecipitation
Mentions: Two promoters are associated with miR-125b-1 transcriptional regulation. The first is in a CpG island close to the miR-125b-1 sequence (Wang et al. 2013). This CpG island has an intermediate CpG content, and thus the transcriptional regulation of miR-125b-1 may be associated with DNA methylation and histone modifications (Weber et al. 2007; Marson et al. 2008). The second promoter is 55 kb upstream from the miR-125b-1 sequence. This promoter, which may regulate the transcription of the miR-125b-1, let-7a-2 and miR-100 genes (Chien et al. 2011), is not in a CpG island, and thus the regulation of these genes may be associated with histone modifications (Fig. 2).Fig. 2

Bottom Line: In this work we investigated the effect of histone modifications on the regulation of this gene promoter.H3K27me3 and H3K9me3 were enriched in MCF7 and MDA-MB-231 cells, respectively.We over-expressed KDM4B/JMJD2B to reactivate this miRNA, resulting in a three-fold increase in miR-125b expression compared with the same cell line without KDM4B/JMJD2B over-expression.

View Article: PubMed Central - PubMed

Affiliation: Unidad de Investigación Biomédica en Cáncer, Instituto Nacional de Cancerología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Avenida San Fernando 22, Mexico City, 14080 Mexico.

ABSTRACT

Purpose: Downregulation of miR-125b-1 is associated with poor prognosis in breast cancer patients. In this work we investigated the effect of histone modifications on the regulation of this gene promoter.

Methods and results: We evaluated the enrichment of two histone modifications involved in gene repression, H3K9me3 and H3K27me3, on the miR-125b-1 promoter in two breast cancer cell lines, MCF7 (luminal A subtype) and MDA-MB-231 (triple-negative subtype), compared to the non-transformed breast cell line MCF10A. H3K27me3 and H3K9me3 were enriched in MCF7 and MDA-MB-231 cells, respectively. Next, we used an EZH2 inhibitor to examine the reactivation of miR-125b-1 in MCF7 cells and evaluated the transcriptional levels of pri-miR-125b-1 and mature miR-125b by qRT-PCR. pri-miRNA and mature miRNA transcripts were both increased after treatment of MCF7 cells with the EZH2 inhibitor, whereas no effect on miR-125b-1 expression levels was observed in MDA-MB-231 and MCF10A cells. We subsequently evaluated the effect of miR-125b-1 reactivation on the expression and protein levels of BAK1, a target of miR-125b. We observed 60 and 70 % decreases in the expression and protein levels of BAK1, respectively, compared to cells that were not treated with the EZH2 inhibitor. We over-expressed KDM4B/JMJD2B to reactivate this miRNA, resulting in a three-fold increase in miR-125b expression compared with the same cell line without KDM4B/JMJD2B over-expression.

Conclusion: The miR-125b-1 is repressed by different epigenetic mechanisms depending on the breast cancer subtype and that miR-125b-1 reactivation specifically eliminates the effect of repressive histone modifications on the expression of an pro-apoptotic target.

No MeSH data available.


Related in: MedlinePlus