Homo sapiens isolate:iSLK219 Transcriptome or Gene expression

Retinoic acid-inducible gene-I (RIG-I) is a cytosolic pathogen recognition receptor that initiates the innate immune response against many RNA viruses. RIG-I also has been shown to sense some DNA viruses, and host RNA polymerase III (RNA Pol III), a cytosolic DNA sensor, converts cytosolic AT-rich DNA into RNA to be sensed by RIG-I. We previously showed that the RIG-I restricts Kaposi Sarcoma-associated herpesvirus (KSHV) reactivation (J Virol. 2014 May;88(10):5778-87). In this study, we report that KSHV stimulates the RIG-I signaling pathway in an RNA Pol III-independent manner and subsequently induces type I IFN responses. Knockdown or inhibition of RNA Pol-III had no effect on IFN-ß induction by KSHV. By using CLIP (Cross-Linking and Immunoprecipitation) and RNA deep sequencing technologies, we identified multiple KSHV regions that give rise to RNA fragments binding to RIG-I, such as ORF810420-10496, ORF6411058-110675, Repeat region (LIR1)119059-119204, and ORF2543561-43650. The sequence dissimilarity between these fragments suggests that RIG-I detects a particular structure rather than a specific sequence motif. Synthesized ORF810420-10496 RNA stimulated RIG-I-dependent but RNA Pol III-independent IFN-ß signaling. In summary, some KSHV viral RNAs are sensed by RIG-I in an RNA Pol III-independent manner.