Upregulation of the cell-cycle regulator RGC-32 in Epstein-Barr virus-immortalized cells

• Published in: PloS one Vol. 6; no. 12; p. e28638
• Main Authors: Schlick, Sandra N, Wood, C David, Gunnell, Andrea, Webb, Helen M, Khasnis, Sarika, Schepers, Aloys, West, Michelle J
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 06.12.2011; Public Library of Science (PLoS)
• Subjects: Analysis; B cells; B-Lymphocytes - metabolism; B-Lymphocytes - virology; Biology; Breast cancer; Burkitt's lymphoma; CDC2 Protein Kinase - biosynthesis; Cell activation; Cell cycle; Cell Cycle Proteins - biosynthesis; Cell Line, Tumor; Colon; Colon cancer; Cooperation; Core Binding Factor Alpha 2 Subunit - biosynthesis; Deoxyribonucleic acid; DNA; Epstein-Barr virus; Flow Cytometry - methods; G2 Phase; Gene expression; Gene Expression Profiling; Genes; Genetic transformation; Health aspects; Herpesvirus 4, Human - metabolism; Humans; Infection; Infections; Kinases; Latency; Latent infection; Life sciences; Lymphocytes; Lymphocytes B; Lymphoma; Lymphomas; Medicine; Muscle Proteins - biosynthesis; Nerve Tissue Proteins - biosynthesis; Ovarian cancer; Ovarian carcinoma; Pathogenesis; Phosphorylation; Plasmids - metabolism; Polyribosomes - metabolism; Protein Biosynthesis; Proteins; Retinal ganglion cells; Ribosomes; RNA; RNA polymerase; RNA, Messenger - metabolism; Tissues; Transcription activation; Transcription, Genetic; Transformation; Translation; Translation initiation; Tumors; Up-Regulation; Viral infections; Viruses; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0028638

Epstein-Barr virus (EBV) is implicated in the pathogenesis of multiple human tumours of lymphoid and epithelial origin. The virus infects and immortalizes B cells establishing a persistent latent infection characterized by varying patterns of EBV latent gene expression (latency 0, I, II and III). The CDK1 activator, Response Gene to Complement-32 (RGC-32, C13ORF15), is overexpressed in colon, breast and ovarian cancer tissues and we have detected selective high-level RGC-32 protein expression in EBV-immortalized latency III cells. Significantly, we show that overexpression of RGC-32 in B cells is sufficient to disrupt G2 cell-cycle arrest consistent with activation of CDK1, implicating RGC-32 in the EBV transformation process. Surprisingly, RGC-32 mRNA is expressed at high levels in latency I Burkitt's lymphoma (BL) cells and in some EBV-negative BL cell-lines, although RGC-32 protein expression is not detectable. We show that RGC-32 mRNA expression is elevated in latency I cells due to transcriptional activation by high levels of the differentially expressed RUNX1c transcription factor. We found that proteosomal degradation or blocked cytoplasmic export of the RGC-32 message were not responsible for the lack of RGC-32 protein expression in latency I cells. Significantly, analysis of the ribosomal association of the RGC-32 mRNA in latency I and latency III cells revealed that RGC-32 transcripts were associated with multiple ribosomes in both cell-types implicating post-initiation translational repression mechanisms in the block to RGC-32 protein production in latency I cells. In summary, our results are the first to demonstrate RGC-32 protein upregulation in cells transformed by a human tumour virus and to identify post-initiation translational mechanisms as an expression control point for this key cell-cycle regulator.