Epstein-Barr Virus BHRF1 Micro- and Stable RNAs during Latency III and after Induction of Replication

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Abstract
Epstein-Barr virus (EBV) microRNAs miR-BHRF1-1, -2, and -3 have been detected in latency III-infected lymphoblasts, where they are encoded within EBNA transcripts (X. Cai, A. Schafer, S. Lu, J. P. Bilello, R. C. Desrosiers, R. Edwards, N. Raab-Traub, and B. R. Cullen, PLoS Pathog. 2:e23, 2006). In latency III-infected lymphoblasts, we have also identified a stable 1.3-kb RNA, which begins 3′ to miR-BHRF1-1, includes the BHRF1 open reading frame, and ends near miR-BHRF1-2. This 1.3-kb RNA is the residue of Drosha cleavage of the BHRF1 microRNAs from EBNA transcripts. Early after induction of EBV replication in latency I-infected Akata lymphoblasts, BHRF1 spliced 1.4-kb mRNA accumulated along with low levels of miR-BHRF1-2 and -3 and a 0.9-kb Drosha or miR-BHRF1-2 cleavage product of BHRF1 mRNA. The turning on of latency III infection at 48 to 72 h after induction of EBV replication was associated with higher miR-BHRF1-1, -2, and -3 levels; accumulation of the 1.3-kb RNA residue in the nucleus; abundant BHRF1 spliced 1.4-kb mRNA in the cytoplasm; and more abundant 0.9-kb mRNA cleavage product in the cytoplasm. These findings implicate miR-BHRF1-2 in 3′ cleavage of BHRF1 mRNA in the cytoplasm and Drosha in cleavage of latency III EBNA and EBV replication-associated BHRF1 transcripts in the nucleus.