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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

Knockdown of c-Myc recovers the miR-23b and miR-27b levels decreased by hypoxia.A, Representative western blot images for c-Myc in the primary cortical neurons pre-transfected with control or c-Myc siRNAs under conditions of normoxia or hypoxia for 6 h. The relative amounts of the c-Myc protein were quantified by densitometry (n = 3, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001). B, Quantitative RT-PCR detection of the expression of mature and primary form of miR-23b and miR-27b in primary cortical neurons pre-transfected with siRNA under conditions of normoxia or hypoxia for 6 h (n = 5, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001). C and D, Representative western blot images for Apaf-1 (C) and quantitative RT-PCR detection of Apaf-1 mRNA expression (D) in the primary cortical neurons pre-transfected with control or c-Myc siRNAs under conditions of normoxia or hypoxia for 24 h. Relative amounts of Apaf-1 protein were quantified by densitometry (n = 3, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001).
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pone.0120217.g005: Knockdown of c-Myc recovers the miR-23b and miR-27b levels decreased by hypoxia.A, Representative western blot images for c-Myc in the primary cortical neurons pre-transfected with control or c-Myc siRNAs under conditions of normoxia or hypoxia for 6 h. The relative amounts of the c-Myc protein were quantified by densitometry (n = 3, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001). B, Quantitative RT-PCR detection of the expression of mature and primary form of miR-23b and miR-27b in primary cortical neurons pre-transfected with siRNA under conditions of normoxia or hypoxia for 6 h (n = 5, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001). C and D, Representative western blot images for Apaf-1 (C) and quantitative RT-PCR detection of Apaf-1 mRNA expression (D) in the primary cortical neurons pre-transfected with control or c-Myc siRNAs under conditions of normoxia or hypoxia for 24 h. Relative amounts of Apaf-1 protein were quantified by densitometry (n = 3, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001).

Mentions: We further sought to investigate the role of c-Myc in neuronal apoptosis induced by hypoxia. Cortical neurons were transfected with the c-Myc siRNA; 48 h later, the neurons received anaerobic treatment (6 h), and we found that knocking down c-Myc expression restored the miR-23b and miR-27b levels (Fig. 5A-B).


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)

Knockdown of c-Myc recovers the miR-23b and miR-27b levels decreased by hypoxia.A, Representative western blot images for c-Myc in the primary cortical neurons pre-transfected with control or c-Myc siRNAs under conditions of normoxia or hypoxia for 6 h. The relative amounts of the c-Myc protein were quantified by densitometry (n = 3, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001). B, Quantitative RT-PCR detection of the expression of mature and primary form of miR-23b and miR-27b in primary cortical neurons pre-transfected with siRNA under conditions of normoxia or hypoxia for 6 h (n = 5, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001). C and D, Representative western blot images for Apaf-1 (C) and quantitative RT-PCR detection of Apaf-1 mRNA expression (D) in the primary cortical neurons pre-transfected with control or c-Myc siRNAs under conditions of normoxia or hypoxia for 24 h. Relative amounts of Apaf-1 protein were quantified by densitometry (n = 3, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4363589&req=5

pone.0120217.g005: Knockdown of c-Myc recovers the miR-23b and miR-27b levels decreased by hypoxia.A, Representative western blot images for c-Myc in the primary cortical neurons pre-transfected with control or c-Myc siRNAs under conditions of normoxia or hypoxia for 6 h. The relative amounts of the c-Myc protein were quantified by densitometry (n = 3, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001). B, Quantitative RT-PCR detection of the expression of mature and primary form of miR-23b and miR-27b in primary cortical neurons pre-transfected with siRNA under conditions of normoxia or hypoxia for 6 h (n = 5, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001). C and D, Representative western blot images for Apaf-1 (C) and quantitative RT-PCR detection of Apaf-1 mRNA expression (D) in the primary cortical neurons pre-transfected with control or c-Myc siRNAs under conditions of normoxia or hypoxia for 24 h. Relative amounts of Apaf-1 protein were quantified by densitometry (n = 3, one-way ANOVA with Newman-Keuls multiple comparison test, ns, not significant, *** P<0.001).
Mentions: We further sought to investigate the role of c-Myc in neuronal apoptosis induced by hypoxia. Cortical neurons were transfected with the c-Myc siRNA; 48 h later, the neurons received anaerobic treatment (6 h), and we found that knocking down c-Myc expression restored the miR-23b and miR-27b levels (Fig. 5A-B).

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