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标题：Circular DNA tumor viruses make circular RNAs
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作者：Tuna Toptan ; Bizunesh Abere ; Michael A. Nalesnik 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2018
卷号：115
期号：37
页码：E8737-E8745
DOI：10.1073/pnas.1811728115
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Epstein−Barr virus (EBV) and Kaposi’s sarcoma herpesvirus (KSHV) cause ∼2% of all human cancers. RNase R-resistant RNA sequencing revealed that both gammaherpesviruses encode multiple, uniquely stable, circular RNAs (circRNA). EBV abundantly expressed both exon-only and exon−intron circRNAs from the BamHI A rightward transcript (BART) locus (circBARTs) formed from a spliced BART transcript and excluding the EBV miRNA region. The circBARTs were expressed in all verified EBV latency types, including EBV-positive posttransplant lymphoproliferative disease, Burkitt lymphoma, nasopharyngeal carcinoma, and AIDS-associated lymphoma tissues and cell lines. Only cells infected with the B95-8 EBV strain, with a 12-kb BART locus deletion, were negative for EBV circBARTs. Less abundant levels of EBV circRNAs originating from LMP2- and BHLF1-encoding genes were also identified. The circRNA sequencing of KSHV-infected primary effusion lymphoma cells revealed a KSHV-encoded circRNA from the vIRF4 locus (circvIRF4) that was constitutively expressed. In addition, KSHV polyadenylated nuclear (PAN) RNA locus generated a swarm (>100) of multiply backspliced, low-abundance RNase R-resistant circRNAs originating in both sense and antisense directions consistent with a novel hyperbacksplicing mechanism. In EBV and KSHV coinfected cells, exon-only EBV circBARTs were located more in the cytoplasm, whereas the intron-retaining circBARTs were found in the nuclear fraction. KSHV circvIRF4 and circPANs were detected in both nuclear and cytoplasmic fractions. Among viral circRNAs tested, none were found in polysome fractions from KSHV−EBV coinfected BC1 cells, although low-abundance protein translation from viral circRNAs could not be excluded. The circRNAs are a new class of viral transcripts expressed in gammaherpesvirus-related tumors that might contribute to viral oncogenesis.
关键词：Epstein−Barr virus ; Kaposi sarcoma virus ; circular RNA ; cancer ; herpesvirus