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MicroRNA-130a associates with ribosomal protein L11 to suppress c-Myc expression in response to UV irradiation.

Li Y, Challagundla KB, Sun XX, Zhang Q, Dai MS - Oncotarget (2015)

Bottom Line: Yet, mechanism underlying UV-induced c-Myc reduction is not completely understood.Overexpression of miR-130a promotes the Ago2 binding to c-myc mRNA, significantly reduces the levels of both c-Myc protein and mRNA and inhibits cell proliferation.Inhibiting miR-130a significantly suppresses UV-mediated c-Myc reduction.

View Article: PubMed Central - PubMed

Affiliation: Departments of Molecular & Medical Genetics, School of Medicine and the OHSU Knight Cancer Institute, Oregon Health & Science University, Portland, OR 97239, USA.

ABSTRACT
The oncoprotein c-Myc is essential for cell growth and proliferation while its deregulated overexpression is associated with most human cancers. Thus tightly regulated levels and activity of c-Myc are critical for maintaining normal cell homeostasis. c-Myc is down-regulated in response to several types of stress, including UV-induced DNA damage. Yet, mechanism underlying UV-induced c-Myc reduction is not completely understood. Here we report that L11 promotes miR-130a targeting of c-myc mRNA to repress c-Myc expression in response to UV irradiation. miR-130a targets the 3'-untranslated region (UTR) of c-myc mRNA. Overexpression of miR-130a promotes the Ago2 binding to c-myc mRNA, significantly reduces the levels of both c-Myc protein and mRNA and inhibits cell proliferation. UV treatment markedly promotes the binding of L11 to miR-130a, c-myc mRNA as well as Ago2 in cells. Inhibiting miR-130a significantly suppresses UV-mediated c-Myc reduction. We further show that L11 is relocalized from the nucleolus to the cytoplasm where it associates with c-myc mRNA upon UV treatment. Together, these results reveal a novel mechanism underlying c-Myc down-regulation in response to UV-mediated DNA damage, wherein L11 promotes miR-130a-loaded miRISC to target c-myc mRNA.

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miR-130a inhibits cell proliferation(A–B) Overexpression of miR-130a inhibits cell cycle progression. U2OS cells were transfected with control or miR-130a mimic for 48 hours. The cells were trypsinized, stained with PI, and analyzed by flow cytometry. The histograms of PI staining from one representative experiment indicating the G1 (2N DNA), G2/M (4N DNA) and S (between G1 and G2/M phases) phases are shown in panel (A). The mean percentages of cells in different cell cycle phases from three independent experiments are shown in panel (B). *p < 0.05; **p < 0.01, compared with control transfected cells. (C–D) BrdU incorporation assays. U2OS cells were transfected with control or miR-130a mimic as above. At 48 hour post-transfection, the cells were incubated with BrdU for another 10 hours. The cells were fixed and stained with anti-BrdU antibodies (red) and DAPI (blue) (C). The average of BrdU-positive cells is shown in (D). **p < 0.01, compared with control transfected cells.
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Figure 4: miR-130a inhibits cell proliferation(A–B) Overexpression of miR-130a inhibits cell cycle progression. U2OS cells were transfected with control or miR-130a mimic for 48 hours. The cells were trypsinized, stained with PI, and analyzed by flow cytometry. The histograms of PI staining from one representative experiment indicating the G1 (2N DNA), G2/M (4N DNA) and S (between G1 and G2/M phases) phases are shown in panel (A). The mean percentages of cells in different cell cycle phases from three independent experiments are shown in panel (B). *p < 0.05; **p < 0.01, compared with control transfected cells. (C–D) BrdU incorporation assays. U2OS cells were transfected with control or miR-130a mimic as above. At 48 hour post-transfection, the cells were incubated with BrdU for another 10 hours. The cells were fixed and stained with anti-BrdU antibodies (red) and DAPI (blue) (C). The average of BrdU-positive cells is shown in (D). **p < 0.01, compared with control transfected cells.

Mentions: To understand the biological function of miR-130a inhibition of c-Myc, we examined whether miR-130a affects cell proliferation. To this end, U2OS cells were transfected with control or miR-130a mimic followed by cell cycle analysis. As shown in Fig 4A and 4B, overexpression of miR-130a significantly reduced the percentage of S phase cells with the concomitant accumulation of G1 phase cells, indicating the inhibition of cell cycle progression by miR-130a. BrdU incorporation assays (Figs. 4C, 4D) also showed significant reduction of S-phase cells by miR-130a transfection. These data clearly indicate that miR-130a negatively regulates cell cycle progression and proliferation.


MicroRNA-130a associates with ribosomal protein L11 to suppress c-Myc expression in response to UV irradiation.

Li Y, Challagundla KB, Sun XX, Zhang Q, Dai MS - Oncotarget (2015)

miR-130a inhibits cell proliferation(A–B) Overexpression of miR-130a inhibits cell cycle progression. U2OS cells were transfected with control or miR-130a mimic for 48 hours. The cells were trypsinized, stained with PI, and analyzed by flow cytometry. The histograms of PI staining from one representative experiment indicating the G1 (2N DNA), G2/M (4N DNA) and S (between G1 and G2/M phases) phases are shown in panel (A). The mean percentages of cells in different cell cycle phases from three independent experiments are shown in panel (B). *p < 0.05; **p < 0.01, compared with control transfected cells. (C–D) BrdU incorporation assays. U2OS cells were transfected with control or miR-130a mimic as above. At 48 hour post-transfection, the cells were incubated with BrdU for another 10 hours. The cells were fixed and stained with anti-BrdU antibodies (red) and DAPI (blue) (C). The average of BrdU-positive cells is shown in (D). **p < 0.01, compared with control transfected cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4359220&req=5

Figure 4: miR-130a inhibits cell proliferation(A–B) Overexpression of miR-130a inhibits cell cycle progression. U2OS cells were transfected with control or miR-130a mimic for 48 hours. The cells were trypsinized, stained with PI, and analyzed by flow cytometry. The histograms of PI staining from one representative experiment indicating the G1 (2N DNA), G2/M (4N DNA) and S (between G1 and G2/M phases) phases are shown in panel (A). The mean percentages of cells in different cell cycle phases from three independent experiments are shown in panel (B). *p < 0.05; **p < 0.01, compared with control transfected cells. (C–D) BrdU incorporation assays. U2OS cells were transfected with control or miR-130a mimic as above. At 48 hour post-transfection, the cells were incubated with BrdU for another 10 hours. The cells were fixed and stained with anti-BrdU antibodies (red) and DAPI (blue) (C). The average of BrdU-positive cells is shown in (D). **p < 0.01, compared with control transfected cells.
Mentions: To understand the biological function of miR-130a inhibition of c-Myc, we examined whether miR-130a affects cell proliferation. To this end, U2OS cells were transfected with control or miR-130a mimic followed by cell cycle analysis. As shown in Fig 4A and 4B, overexpression of miR-130a significantly reduced the percentage of S phase cells with the concomitant accumulation of G1 phase cells, indicating the inhibition of cell cycle progression by miR-130a. BrdU incorporation assays (Figs. 4C, 4D) also showed significant reduction of S-phase cells by miR-130a transfection. These data clearly indicate that miR-130a negatively regulates cell cycle progression and proliferation.

Bottom Line: Yet, mechanism underlying UV-induced c-Myc reduction is not completely understood.Overexpression of miR-130a promotes the Ago2 binding to c-myc mRNA, significantly reduces the levels of both c-Myc protein and mRNA and inhibits cell proliferation.Inhibiting miR-130a significantly suppresses UV-mediated c-Myc reduction.

View Article: PubMed Central - PubMed

Affiliation: Departments of Molecular & Medical Genetics, School of Medicine and the OHSU Knight Cancer Institute, Oregon Health & Science University, Portland, OR 97239, USA.

ABSTRACT
The oncoprotein c-Myc is essential for cell growth and proliferation while its deregulated overexpression is associated with most human cancers. Thus tightly regulated levels and activity of c-Myc are critical for maintaining normal cell homeostasis. c-Myc is down-regulated in response to several types of stress, including UV-induced DNA damage. Yet, mechanism underlying UV-induced c-Myc reduction is not completely understood. Here we report that L11 promotes miR-130a targeting of c-myc mRNA to repress c-Myc expression in response to UV irradiation. miR-130a targets the 3'-untranslated region (UTR) of c-myc mRNA. Overexpression of miR-130a promotes the Ago2 binding to c-myc mRNA, significantly reduces the levels of both c-Myc protein and mRNA and inhibits cell proliferation. UV treatment markedly promotes the binding of L11 to miR-130a, c-myc mRNA as well as Ago2 in cells. Inhibiting miR-130a significantly suppresses UV-mediated c-Myc reduction. We further show that L11 is relocalized from the nucleolus to the cytoplasm where it associates with c-myc mRNA upon UV treatment. Together, these results reveal a novel mechanism underlying c-Myc down-regulation in response to UV-mediated DNA damage, wherein L11 promotes miR-130a-loaded miRISC to target c-myc mRNA.

Show MeSH
Related in: MedlinePlus