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The transcription factor c-Myc suppresses MiR-23b and MiR-27b transcription during fetal distress and increases the sensitivity of neurons to hypoxia-induced apoptosis.

Chen Q, Zhang F, Wang Y, Liu Z, Sun A, Zen K, Zhang CY, Zhang Q - PLoS ONE (2015)

Bottom Line: However, the mechanism underlying this downregulation is not completely understood.Second, forced overexpression or knockdown of c-Myc could suppress or increase the expression of miR-23b-27b cluster polynucleotides.Finally, we showed that elevated c-Myc expression led to an increase in the Apaf-1 level by suppressing miR-23b-27b cluster expression and that this enhanced neuronal sensitivity to apoptosis.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pharmaceutical Biotechnology, Jiangsu Engineering Research Center for microRNA Biology and Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China.

ABSTRACT
Previous studies reported that the expression of miR-23b-27b cluster was downregulated in embryonic brain cortices during hypoxia-induced neuronal apoptosis. However, the mechanism underlying this downregulation is not completely understood. Here, we report that the transcription factor c-Myc plays an important role in regulating the expression of miR-23b-27b cluster during hypoxia. First, the c-Myc protein level was significantly elevated in embryonic brain cortices in a mouse model of fetal distress. Second, forced overexpression or knockdown of c-Myc could suppress or increase the expression of miR-23b-27b cluster polynucleotides. Third, we identified 2 conserved c-Myc binding sites (E-boxes) in the enhancer and promoter regions of miR-23b-27b cluster in the mouse genome. Finally, we showed that elevated c-Myc expression led to an increase in the Apaf-1 level by suppressing miR-23b-27b cluster expression and that this enhanced neuronal sensitivity to apoptosis. In summary, our study demonstrates that c-Myc may suppress the expression of the miR-23b-27b cluster, resulting in additional neuronal apoptosis during hypoxia.

No MeSH data available.


Related in: MedlinePlus

c-Myc acts on E-Boxes in the promoter of the miR-23b-27b cluster.A, Diagram representing the c-Myc binding sites in the miR-23b-27b cluster promoter region. B and C, ChIP assays were performed by IP with either anti-c-Myc antibody or control IgG. D, c-Myc regulates the promoter of the miR-23b-27b cluster. For the luciferase reporter assay, cells were co-transfected with empty vector or c-Myc plasmids and the luciferase reporter plasmid carrying promoter constructs containing site 1 or site 1 mutant (n = 3, unpaired t-test, ns, not significant,** P < 0.01).
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pone.0120217.g004: c-Myc acts on E-Boxes in the promoter of the miR-23b-27b cluster.A, Diagram representing the c-Myc binding sites in the miR-23b-27b cluster promoter region. B and C, ChIP assays were performed by IP with either anti-c-Myc antibody or control IgG. D, c-Myc regulates the promoter of the miR-23b-27b cluster. For the luciferase reporter assay, cells were co-transfected with empty vector or c-Myc plasmids and the luciferase reporter plasmid carrying promoter constructs containing site 1 or site 1 mutant (n = 3, unpaired t-test, ns, not significant,** P < 0.01).

Mentions: Because we demonstrated that c-Myc suppressed the expression of miR-23b and miR-27b, we next tested whether c-Myc could directly bind to the promoter region of miR-23b-27b cluster. We searched for the DNA response elements (the binding sites for c-Myc) in the genomic region containing the miRNA promoter. Approximately thirty kilobases of DNA sequence on chromosome 13 upstream of the mir-23b-27b cluster was analyzed for putative c-Myc-binding sites. c-Myc is known to bind to the canonical E-box sequence CACGTG, and we identified three putative binding sites matching sequence at 4 kb, 13 kb and 25 kb upstream from the transcriptional starting site (Fig. 4A).


The transcription factor c-Myc suppresses MiR-23b and MiR-27b transcription during fetal distress and increases the sensitivity of neurons to hypoxia-induced apoptosis.

Chen Q, Zhang F, Wang Y, Liu Z, Sun A, Zen K, Zhang CY, Zhang Q - PLoS ONE (2015)

c-Myc acts on E-Boxes in the promoter of the miR-23b-27b cluster.A, Diagram representing the c-Myc binding sites in the miR-23b-27b cluster promoter region. B and C, ChIP assays were performed by IP with either anti-c-Myc antibody or control IgG. D, c-Myc regulates the promoter of the miR-23b-27b cluster. For the luciferase reporter assay, cells were co-transfected with empty vector or c-Myc plasmids and the luciferase reporter plasmid carrying promoter constructs containing site 1 or site 1 mutant (n = 3, unpaired t-test, ns, not significant,** P < 0.01).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4363589&req=5

pone.0120217.g004: c-Myc acts on E-Boxes in the promoter of the miR-23b-27b cluster.A, Diagram representing the c-Myc binding sites in the miR-23b-27b cluster promoter region. B and C, ChIP assays were performed by IP with either anti-c-Myc antibody or control IgG. D, c-Myc regulates the promoter of the miR-23b-27b cluster. For the luciferase reporter assay, cells were co-transfected with empty vector or c-Myc plasmids and the luciferase reporter plasmid carrying promoter constructs containing site 1 or site 1 mutant (n = 3, unpaired t-test, ns, not significant,** P < 0.01).
Mentions: Because we demonstrated that c-Myc suppressed the expression of miR-23b and miR-27b, we next tested whether c-Myc could directly bind to the promoter region of miR-23b-27b cluster. We searched for the DNA response elements (the binding sites for c-Myc) in the genomic region containing the miRNA promoter. Approximately thirty kilobases of DNA sequence on chromosome 13 upstream of the mir-23b-27b cluster was analyzed for putative c-Myc-binding sites. c-Myc is known to bind to the canonical E-box sequence CACGTG, and we identified three putative binding sites matching sequence at 4 kb, 13 kb and 25 kb upstream from the transcriptional starting site (Fig. 4A).

Bottom Line: However, the mechanism underlying this downregulation is not completely understood.Second, forced overexpression or knockdown of c-Myc could suppress or increase the expression of miR-23b-27b cluster polynucleotides.Finally, we showed that elevated c-Myc expression led to an increase in the Apaf-1 level by suppressing miR-23b-27b cluster expression and that this enhanced neuronal sensitivity to apoptosis.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pharmaceutical Biotechnology, Jiangsu Engineering Research Center for microRNA Biology and Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China.

ABSTRACT
Previous studies reported that the expression of miR-23b-27b cluster was downregulated in embryonic brain cortices during hypoxia-induced neuronal apoptosis. However, the mechanism underlying this downregulation is not completely understood. Here, we report that the transcription factor c-Myc plays an important role in regulating the expression of miR-23b-27b cluster during hypoxia. First, the c-Myc protein level was significantly elevated in embryonic brain cortices in a mouse model of fetal distress. Second, forced overexpression or knockdown of c-Myc could suppress or increase the expression of miR-23b-27b cluster polynucleotides. Third, we identified 2 conserved c-Myc binding sites (E-boxes) in the enhancer and promoter regions of miR-23b-27b cluster in the mouse genome. Finally, we showed that elevated c-Myc expression led to an increase in the Apaf-1 level by suppressing miR-23b-27b cluster expression and that this enhanced neuronal sensitivity to apoptosis. In summary, our study demonstrates that c-Myc may suppress the expression of the miR-23b-27b cluster, resulting in additional neuronal apoptosis during hypoxia.

No MeSH data available.


Related in: MedlinePlus