Degradation of cellular mir-27 by a novel, highly abundant viral transcript is important for efficient virus replication in vivo.

• Main Authors: Lisa Marcinowski, Mélanie Tanguy, Astrid Krmpotic, Bernd Rädle, Vanda J Lisnić, Lee Tuddenham, Béatrice Chane-Woon-Ming, Zsolt Ruzsics, Florian Erhard, Corinna Benkartek, Marina Babic, Ralf Zimmer, Joanne Trgovcich, Ulrich H Koszinowski, Stipan Jonjic, Sébastien Pfeffer, Lars Dölken
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2012-02-01
• Series: PLoS Pathogens
• Online Access: https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22346748/pdf/?tool=EBI
• ISSN: 1553-7366; 1553-7374

Cytomegaloviruses express large amounts of viral miRNAs during lytic infection, yet, they only modestly alter the cellular miRNA profile. The most prominent alteration upon lytic murine cytomegalovirus (MCMV) infection is the rapid degradation of the cellular miR-27a and miR-27b. Here, we report that this regulation is mediated by the ∼1.7 kb spliced and highly abundant MCMV m169 transcript. Specificity to miR-27a/b is mediated by a single, apparently optimized, miRNA binding site located in its 3'-UTR. This site is easily and efficiently retargeted to other cellular and viral miRNAs by target site replacement. Expression of the 3'-UTR of m169 by an adenoviral vector was sufficient to mediate its function, indicating that no other viral factors are essential in this process. Degradation of miR-27a/b was found to be accompanied by 3'-tailing and -trimming. Despite its dramatic effect on miRNA stability, we found this interaction to be mutual, indicating potential regulation of m169 by miR-27a/b. Most interestingly, three mutant viruses no longer able to target miR-27a/b, either due to miRNA target site disruption or target site replacement, showed significant attenuation in multiple organs as early as 4 days post infection, indicating that degradation of miR-27a/b is important for efficient MCMV replication in vivo.