Repression of VEGFA by CA-rich element-binding microRNAs is modulated by hnRNP L

EMBO J. 2011 Apr 6;30(7):1324-34. doi: 10.1038/emboj.2011.38. Epub 2011 Feb 22.

Abstract

Expression of vascular endothelial growth factor-A (VEGFA) by tumour-associated macrophages is critical for tumour progression and metastasis. Hypoxia, a common feature of the neoplastic microenvironment, induces VEGFA expression by increased transcription, translation, and mRNA stabilization. Here, we report a new mechanism of VEGFA regulation by hypoxia that involves reversal of microRNA (miRNA)-mediated silencing of VEGFA expression. We show that the CA-rich element (CARE) in the human VEGFA 3'-UTR is targeted by at least four miRNAs. Among these miRNAs, miR-297 and -299 are endogenously expressed in monocytic cells and negatively regulate VEGFA expression. Unexpectedly, hypoxia completely reverses miRNA-mediated repression of VEGFA expression. We show that heterogeneous nuclear ribonucleoprotein L (hnRNP L), which also binds the VEGFA 3'-UTR CARE, prevents miRNA silencing activity. Hypoxia induces translocation of nuclear hnRNP L to the cytoplasm, which markedly increases hnRNP L binding to VEGFA mRNA thereby inhibiting miRNA activity. In summary, we describe a novel regulatory mechanism in which the interplay between miRNAs and RNA-binding proteins influences expression of a critical hypoxia-inducible angiogenic protein. These studies may contribute to provide miRNA-based anticancer therapeutic tools.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions
  • Cell Line, Tumor
  • Gene Expression Regulation*
  • Heterogeneous-Nuclear Ribonucleoprotein L / metabolism*
  • Humans
  • Hypoxia
  • MicroRNAs / metabolism*
  • Models, Biological
  • Vascular Endothelial Growth Factor A / biosynthesis*

Substances

  • 3' Untranslated Regions
  • Heterogeneous-Nuclear Ribonucleoprotein L
  • MicroRNAs
  • VEGFA protein, human
  • Vascular Endothelial Growth Factor A