Limits...
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.

Show MeSH

Related in: MedlinePlus

miR-130a regulates c-Myc levels(A–B) Overexpression of miR-130a decreases c-Myc levels. U2OS (A) or WI38 (B) cells transfected with control or miR-130a mimics were assayed for the relative expression of miR-130a normalized with U6 snRNA (top panels), c-myc mRNA normalized with GAPDH mRNA (middle panels) by RT-qPCR, and c-Myc protein levels (bottom panels) by IB. *p < 0.01, compared with control transfected cells. (C–D) Inhibition of miR-130a increases c-Myc levels. U2OS (C) or WI38 (D) cells transfected with control or miR-130a hairpin inhibitors were assayed for the relative expression of c-myc mRNA normalized with GAPDH mRNA (middle panels) by RT-qPCR and c-Myc protein expression (bottom panels) by IB. *p < 0.01, compared with control transfected cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4359220&req=5

Figure 2: miR-130a regulates c-Myc levels(A–B) Overexpression of miR-130a decreases c-Myc levels. U2OS (A) or WI38 (B) cells transfected with control or miR-130a mimics were assayed for the relative expression of miR-130a normalized with U6 snRNA (top panels), c-myc mRNA normalized with GAPDH mRNA (middle panels) by RT-qPCR, and c-Myc protein levels (bottom panels) by IB. *p < 0.01, compared with control transfected cells. (C–D) Inhibition of miR-130a increases c-Myc levels. U2OS (C) or WI38 (D) cells transfected with control or miR-130a hairpin inhibitors were assayed for the relative expression of c-myc mRNA normalized with GAPDH mRNA (middle panels) by RT-qPCR and c-Myc protein expression (bottom panels) by IB. *p < 0.01, compared with control transfected cells.

Mentions: miR-130a has recently been shown to suppress cancer cell growth and invasion through targeting the proto-oncogene MET [43] and several components in the mitogen-activated protein kinase (MAPK) pathway [44]. Therefore, we next examined whether miR-130a regulates c-Myc levels. As shown in Fig. 2A, overexpression of miR-130a significantly reduced the levels of both c-Myc protein and mRNA, compared to the negative mimic control, in U2OS cells. Conversely, suppression of endogenous miR-130a in U2OS cells by transfecting with miRIDIAN miR-130a hairpin inhibitor increased the levels of both c-Myc protein and mRNA as compared to the negative inhibitor control (Fig. 2C). Similar effects were also observed in primary human fibroblast WI38 cells (Figs. 2B and 2D), suggesting that the inhibition of c-Myc by miR-130a is not cell type-specific effect.


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 regulates c-Myc levels(A–B) Overexpression of miR-130a decreases c-Myc levels. U2OS (A) or WI38 (B) cells transfected with control or miR-130a mimics were assayed for the relative expression of miR-130a normalized with U6 snRNA (top panels), c-myc mRNA normalized with GAPDH mRNA (middle panels) by RT-qPCR, and c-Myc protein levels (bottom panels) by IB. *p < 0.01, compared with control transfected cells. (C–D) Inhibition of miR-130a increases c-Myc levels. U2OS (C) or WI38 (D) cells transfected with control or miR-130a hairpin inhibitors were assayed for the relative expression of c-myc mRNA normalized with GAPDH mRNA (middle panels) by RT-qPCR and c-Myc protein expression (bottom panels) by IB. *p < 0.01, compared with control transfected cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: miR-130a regulates c-Myc levels(A–B) Overexpression of miR-130a decreases c-Myc levels. U2OS (A) or WI38 (B) cells transfected with control or miR-130a mimics were assayed for the relative expression of miR-130a normalized with U6 snRNA (top panels), c-myc mRNA normalized with GAPDH mRNA (middle panels) by RT-qPCR, and c-Myc protein levels (bottom panels) by IB. *p < 0.01, compared with control transfected cells. (C–D) Inhibition of miR-130a increases c-Myc levels. U2OS (C) or WI38 (D) cells transfected with control or miR-130a hairpin inhibitors were assayed for the relative expression of c-myc mRNA normalized with GAPDH mRNA (middle panels) by RT-qPCR and c-Myc protein expression (bottom panels) by IB. *p < 0.01, compared with control transfected cells.
Mentions: miR-130a has recently been shown to suppress cancer cell growth and invasion through targeting the proto-oncogene MET [43] and several components in the mitogen-activated protein kinase (MAPK) pathway [44]. Therefore, we next examined whether miR-130a regulates c-Myc levels. As shown in Fig. 2A, overexpression of miR-130a significantly reduced the levels of both c-Myc protein and mRNA, compared to the negative mimic control, in U2OS cells. Conversely, suppression of endogenous miR-130a in U2OS cells by transfecting with miRIDIAN miR-130a hairpin inhibitor increased the levels of both c-Myc protein and mRNA as compared to the negative inhibitor control (Fig. 2C). Similar effects were also observed in primary human fibroblast WI38 cells (Figs. 2B and 2D), suggesting that the inhibition of c-Myc by miR-130a is not cell type-specific effect.

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