TY - JOUR T1 - Editing of Epstein-Barr virus-encoded BART6 microRNAs controls their dicer targeting and consequently affects viral latency. JF - J Biol Chem Y1 - 2010 A1 - Iizasa, Hisashi A1 - Wulff, Bjorn-Erik A1 - Alla, Nageswara R A1 - Maragkakis, Manolis A1 - Megraw, Molly A1 - Hatzigeorgiou, Artemis A1 - Iwakiri, Dai A1 - Takada, Kenzo A1 - Wiedmer, Andreas A1 - Showe, Louise A1 - Lieberman, Paul A1 - Nishikura, Kazuko KW - Cell Line, Tumor KW - Epstein-Barr Virus Infections KW - Epstein-Barr Virus Nuclear Antigens KW - Gene Silencing KW - Herpesvirus 4, Human KW - Humans KW - Immediate-Early Proteins KW - MicroRNAs KW - Ribonuclease III KW - RNA Editing KW - RNA, Viral KW - Trans-Activators KW - Viral Proteins KW - Virus Latency AB -

Certain primary transcripts of miRNA (pri-microRNAs) undergo RNA editing that converts adenosine to inosine. The Epstein-Barr virus (EBV) genome encodes multiple microRNA genes of its own. Here we report that primary transcripts of ebv-miR-BART6 (pri-miR-BART6) are edited in latently EBV-infected cells. Editing of wild-type pri-miR-BART6 RNAs dramatically reduced loading of miR-BART6-5p RNAs onto the microRNA-induced silencing complex. Editing of a mutation-containing pri-miR-BART6 found in Daudi Burkitt lymphoma and nasopharyngeal carcinoma C666-1 cell lines suppressed processing of miR-BART6 RNAs. Most importantly, miR-BART6-5p RNAs silence Dicer through multiple target sites located in the 3'-UTR of Dicer mRNA. The significance of miR-BART6 was further investigated in cells in various stages of latency. We found that miR-BART6-5p RNAs suppress the EBNA2 viral oncogene required for transition from immunologically less responsive type I and type II latency to the more immunoreactive type III latency as well as Zta and Rta viral proteins essential for lytic replication, revealing the regulatory function of miR-BART6 in EBV infection and latency. Mutation and A-to-I editing appear to be adaptive mechanisms that antagonize miR-BART6 activities.

VL - 285 IS - 43 ER - TY - JOUR T1 - Frequency and fate of microRNA editing in human brain. JF - Nucleic Acids Res Y1 - 2008 A1 - Kawahara, Yukio A1 - Megraw, Molly A1 - Kreider, Edward A1 - Iizasa, Hisashi A1 - Valente, Louis A1 - Hatzigeorgiou, Artemis G A1 - Nishikura, Kazuko KW - Adenosine KW - Adenosine Deaminase KW - Animals KW - Base Sequence KW - Brain KW - Humans KW - Inosine KW - Mice KW - MicroRNAs KW - Molecular Sequence Data KW - RNA Editing KW - RNA Precursors KW - RNA Processing, Post-Transcriptional KW - RNA-Binding Proteins AB -

Primary transcripts of certain microRNA (miRNA) genes (pri-miRNAs) are subject to RNA editing that converts adenosine to inosine (A-->I RNA editing). However, the frequency of the pri-miRNA editing and the fate of edited pri-miRNAs remain largely to be determined. Examination of already known pri-miRNA editing sites indicated that adenosine residues of the UAG triplet sequence might be edited more frequently. In the present study, therefore, we conducted a large-scale survey of human pri-miRNAs containing the UAG triplet sequence. By direct sequencing of RT-PCR products corresponding to pri-miRNAs, we examined 209 pri-miRNAs and identified 43 UAG and also 43 non-UAG editing sites in 47 pri-miRNAs, which were highly edited in human brain. In vitro miRNA processing assay using recombinant Drosha-DGCR8 and Dicer-TRBP (the human immuno deficiency virus transactivating response RNA-binding protein) complexes revealed that a majority of pri-miRNA editing is likely to interfere with the miRNA processing steps. In addition, four new edited miRNAs with altered seed sequences were identified by targeted cloning and sequencing of the miRNAs that would be processed from edited pri-miRNAs. Our studies predict that approximately 16% of human pri-miRNAs are subject to A-->I editing and, thus, miRNA editing could have a large impact on the miRNA-mediated gene silencing.

VL - 36 IS - 16 ER -