Growth-promoting properties of Epstein-Barr virus EBER-1 RNA correlate with ribosomal protein L22 binding.
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.
Houmani
Jennifer L
JL
Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA.
Davis
Christopher I
CI
Ruf
Ingrid K
IK
D001483:Base Sequence; D001665:Binding Sites; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D006367:HeLa Cells; D004854:Herpesvirus 4, Human / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D012367:RNA, Viral / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid
C099537:Epstein-Barr virus encoded RNA 1; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D012269:Ribosomal Proteins; C067169:RPL22 protein, human