Growth-promoting properties of Epstein-Barr virus EBER-1 RNA correlate with ribosomal protein L22 binding

J Virol. 2009 Oct;83(19):9844-53. doi: 10.1128/JVI.01014-09. Epub 2009 Jul 29.

Abstract

The Epstein-Barr virus (EBV)-encoded RNAs, EBER-1 and EBER-2, are highly abundant noncoding nuclear RNAs expressed during all forms of EBV latency. The EBERs have been shown to impart significant tumorigenic potential upon EBV-negative Burkitt lymphoma (BL) cells and to contribute to the growth potential of other B-cell lymphoma-, gastric carcinoma-, and nasopharyngeal carcinoma-derived cell lines. However, the mechanisms underlying this EBER-dependent enhancement of cell growth potential remain to be elucidated. Here we focused on the known interaction between EBER-1 and the cellular ribosomal protein L22 and the consequences of this interaction with respect to the growth-promoting properties of the EBERs. L22, a component of 60S ribosomal subunits, binds three sites on EBER-1, and a substantial fraction of available L22 is relocalized from nucleoli to the nucleoplasm in EBV-infected cells. To investigate the hypothesis that EBER-1-mediated relocalization of L22 in EBV-infected cells is critical for EBER-dependent functions, we investigated whether EBER-1 expression is necessary and sufficient for nucleoplasmic retention of L22. Following demonstration of this, we utilized RNA-protein binding assays and fluorescence localization studies to demonstrate that mutation of the L22 binding sites on EBER-1 prevents L22 binding and inhibits EBER-1-dependent L22 relocalization. Finally, the in vivo consequence of preventing L22 relocalization in EBER-expressing cells was examined in soft agar colony formation assays. We demonstrate that BL cells expressing mutated EBER-1 RNAs rendered incapable of binding L22 have significantly reduced capacity to enhance cell growth potential relative to BL cells expressing wild-type EBERs.

Publication types

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

MeSH terms

  • Base Sequence
  • Binding Sites
  • Cell Line, Tumor
  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism
  • HeLa Cells
  • Herpesvirus 4, Human / metabolism*
  • Humans
  • Models, Biological
  • Molecular Sequence Data
  • Mutation
  • Nucleic Acid Conformation
  • RNA, Viral / metabolism*
  • RNA-Binding Proteins / metabolism*
  • Ribosomal Proteins / metabolism*
  • Sequence Homology, Nucleic Acid

Substances

  • Epstein-Barr virus encoded RNA 1
  • RNA, Viral
  • RNA-Binding Proteins
  • Ribosomal Proteins
  • RPL22 protein, human