Roles of ADAR and RNA editing in host-virus interaction and associated diseases

RNA editing events mediated by the ADAR family proteins constitute an integral step in generating the complexity and diversity of cellular RNA signatures, but the physiological consequences are largely unknown. Interestingly, given its interferon inducibility and previously described function of editing the viral RNA, ADAR1 represents a potentially critical determinant in the host response to viral infection and associated pathophysiology. Our recent high-throughput sequencing studies unveiled hitherto unrecognized RNA A-to-I(G) editing events on several gene transcripts implicated in the innate antiviral response, implying an ADAR1-based regulatory mechanism that underlies the cellular response to virus intrusion. However, the molecular mechanisms and cellular relevance of such regulatory circuitry are largely unresolved. In particular, what mode of regulation is achieved molecularly, how the genetic information recoding is manifested at the RNA and cellular level, and how this post-transcriptional regulation of innate immunity genes is coordinated with its physiological or pathophysiological roles remain to be answered. In this proposal, we have outlined and executed a set of synergistic experiments to further explore the interplay between RNA editing and innate antiviral mechanism. Overall, these studies will extend our understanding of the cellular role of ADAR1 and the regulation of RNA editing in general, taking it to new levels at which function is explored in a disease context. By establishing the regulatory network of ADAR1 in host-virus interaction and its pathophysiological relevance, these studies may have tremendous potential for the development of new therapeutic schemes for diseases or conditions associated with virus intrusion. A major goal of this research proposal is to ascertain the involvement of ADAR1 in the regulation of innate immunity by identifying its potential host targets. In the second year of the funding period, we have thoroughly analyzed the results from the next-generation RNA-Seq approach, from which a list of potential editing targets of ADAR1 has been outlined. Interestingly, a few of the confirmed candidate genes are functionally linked to virus RNA recognition, thereby implicating ADAR1 in the process of anti-viral defense. A key finding of our recent work is the detection of expression and A-to-I(G) editing of these RNA transcripts. Using Sanger sequencing, we were able to locate many novel edits that are targeted by the ADAR1 enzyme, Furthermore, our data revealed that ADAR1 was dispensable for RNA expression of target transcripts, but important for maintaining proper expression and translation levels of the protein products of the target genes. RNA immunoprecipitation assay further pinpointed a direction association of ADAR1 with the target mRNA transcripts. Together, these observations thus imply a role of this adenosine deaminase in the associated cellular pathway. We have also started to focus on the functional and mechanistic characterization of the altered editing events.

Project ID:PG10501-0414
External Project ID:NHRI-EX105-10321SI