Kaposi's Sarcoma-Associated Herpesvirus-Encoded circRNAs Are Expressed in Infected Tumor Tissues and Are Incorporated into Virions
Kaposi's Sarcoma-Associated Herpesvirus-Encoded circRNAs Are Expressed in Infected Tumor Tissues and Are Incorporated into Virions
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DOI：
10.1128/mbio.03027-19
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发表时间：
2020-01-01
期刊：
影响因子：
6.4
通讯作者：
Chang, Yuan
中科院分区：
文献类型：
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作者：
Abere, Bizunesh;Li, Jinghui;Chang, Yuan
最近发现卡波西肉瘤相关疱疹病毒（KSHV）从几个KSHV基因中产生环状RNA（circRNA），最丰富的是K10（病毒干扰素调节因子4 [vIRF 4]），K7.3和多聚腺苷酸化核（PAN）RNA。为了确定这些circRNA的表达，检查了KSHV感染的细胞系、患者组织和纯化的病毒体。在6种原发性渗出性淋巴瘤（PEL）细胞系的检测中普遍检测到KSHV circRNA表达，但范围从紧密潜伏的KSHV和EB病毒双重感染的BC-1细胞中的低水平表达到仅KSHV的BCBL-1细胞中的大量表达，并自发产生病毒。一般来说，PAN/K7.3基因座广泛且双向地产生高于相应线性RNA水平的circRNA水平。然而，尽管线性vIRF 4 RNA被病毒诱导激活，但对应于特定KSHV环化位点（circ-vIRF 4）的RNA被最小程度地诱导。原位杂交显示，丰富的circ-vIRF 4在非诱导的PEL细胞。所有三种KSHV circRNA均以核酸酶保护形式从收集自用KSHV分子克隆感染的BrK. 219细胞的梯度纯化病毒体中分离。对于circ-vIRF 4，输出到细胞质的完全加工形式被掺入病毒颗粒中，但保留内含子的核形式没有。circ-vIRF 4的半衰期是其线性对应物的半衰期的两倍。通过原位杂交和逆转录-PCR（RT-PCR）检测保存超过25年的血清中的KSHV circRNA，其检出率高于相应的线性对应物。综上所述，KSHV circRNA在感染相关疾病中表达，可根据病毒的生命周期进行调控，并被整合到病毒颗粒中进行预先递送，提示其在早期感染中具有潜在功能。重要性KSHV最近被发现编码circRNA。circRNA由上游前体mRNA剪接供体外显子-内含子连接到受体位点的反向剪接产生，产生共价闭合的环。这项研究表明，对于一个KSHV区域，PAN/K7.3基因座，广泛和双向产生的circRNA水平平行于相应的线性RNA水平。然而，另一个KSHV环化位点（circ-vIRF 4）显示出与相应线性RNA不同的表达。所有KSHV circRNA都被整合到KSHV病毒体中，并在新感染的细胞中潜在地表达为立即早期产物。
Kaposi's sarcoma-associated herpesvirus (KSHV) has recently been found to generate circular RNAs (circRNAs) from several KSHV genes, most abundantly from K10 (viral interferon regulatory factor 4 [vIRF4]), K7.3, and polyadenylated nuclear (PAN) RNA. To define expression of these circRNAs, KSHV-infected cell lines, patient tissues, and purified virions were examined. KSHV circRNA expression was universally detected in tests of six primary effusion lymphoma (PEL) cell lines but ranged from low-level expression in BC-1 cells dually infected with tightly latent KSHV and Epstein-Barr virus to abundant expression in KSHV-only BCBL-1 cells with spontaneous virus production. Generally, the PAN/K7.3 locus broadly and bidirectionally generated circRNA levels that paralleled the corresponding linear RNA levels. However, RNA corresponding to a particular KSHV circularization site (circ-vIRF4) was minimally induced, despite linear vIRF4 RNA being activated by virus induction. In situ hybridization showed abundant circ-vIRF4 in noninduced PEL cells. All three KSHV circRNAs were isolated as nuclease-protected forms from gradient-purified virions collected from BrK.219 cells infected with a KSHV molecular clone. For circ-vIRF4, the fully processed form that is exported to the cytoplasm was incorporated into virus particles but the nuclear, intron-retaining form was not. The half-life of circ-vIRF4 was twice as long as that of its linear counterpart. The KSHV circRNAs could be detected at a higher rate than their corresponding linear counterparts by in situ hybridization in archival tissues and by reverse transcription-PCR (RT-PCR) in sera stored for over 25 years. In summary, KSHV circRNAs are expressed in infection-associated diseases, can be regulated depending on virus life cycle, and are incorporated into viral particles for preformed delivery, suggesting a potential function in early infection.IMPORTANCE KSHV has recently been found to encode circRNAs. circRNAs result from back-splicing of an upstream pre-mRNA splice donor exon-intron junction to an acceptor site, generating a covalently closed circle. This study revealed that for one KSHV region, the PAN/K7.3 locus, broadly and bidirectionally generated circRNA levels parallel corresponding linear RNA levels. Another KSHV circularization site (circ-vIRF4), however, showed expression that differed from that of the corresponding linear RNA. All KSHV circRNAs are incorporated into KSHV virions and are potentially expressed as immediate early products in newly infected cells.