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Mol Cell Biochem. 2016 Jun;417(1-2):141-53. doi: 10.1007/s11010-016-2721-2. Epub 2016 May 25.

Regulation of nucleolin expression by miR-194, miR-206, and HuR.

Author information

  • 1Department of Biochemistry and Molecular Biology, Medical University of South Carolina, P. O. Box 250509, Charleston, SC, 29425, USA.
  • 2Amity Centre for Medical Biotechnology, Amity Institute of Biotechnology, Amity University, Gautam Buddha Nagar Sec-125, Noida, 201301, India.
  • 3College of Medicine, Medical University of South Carolina, Charleston, SC, 29425, USA.
  • 4Division of Gastroenterology and Hepatology, Department of Medicine, Medical University of South Carolina, Charleston, SC, 29425, USA.
  • 5Department of Biochemistry and Molecular Biology, Medical University of South Carolina, P. O. Box 250509, Charleston, SC, 29425, USA. tholanik@musc.edu.

Abstract

Nucleolin is a proliferation-associated protein that is overexpressed in multiple types of cancer. The mechanisms leading to overexpression of nucleolin in specific cancers are not fully understood. This study found that nucleolin is notably elevated in breast cancer cell lines MCF-7 and MDA-231 compared to nonmalignant breast epithelial MCF-10A cells. In silico analyses revealed the presence of putative binding sites for microRNAs miR-194 and miR-206 in the 3'-untranslated region (3'-UTR) of Ncl mRNA. Transfection of the three cell lines with pre-miR-194 or pre-miR-206 specifically decreased the Ncl mRNA and protein expression. Treatments of the cells with antagomiR-194 or antagomiR-206 upregulated nucleolin expression ~2- to 3-fold. Co-transfection of cells with a reporter vector containing the Ncl 3'-UTR downstream from the Renilla luciferase gene and pre-miR-194 or pre-miR-206 led to a ~3-fold decrease in Renilla/firefly luciferase activity. Cytoplasmic levels of the RNA-binding protein HuR were higher in MCF-7 and MDA-231 cells than those in MCF-10A cells. RNA immunoprecipitation assays demonstrated that HuR binds to Ncl mRNA in all the three cell types. ShRNA-mediated knock-down of HuR induced a decrease in nucleolin expression, while exogenous expression of HuR led to upregulation of nucleolin expression. Analysis of the polysome-monosome distribution of Ncl mRNA in HuR knock-down cells demonstrated that HuR enhances the translation efficiency of Ncl mRNA. These findings demonstrate that nucleolin expression is down-regulated by miR-194 and miR-206 and upregulated by HuR.

KEYWORDS:

Breast cancer cells; MicroRNAs and RNA-binding proteins; Post-transcriptional control; Translational regulation of mRNA

PMID:
27221739
DOI:
10.1007/s11010-016-2721-2
[PubMed - in process]
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