This project focuses on understanding the natural role of RNA interference (RNAi) in divergent organisms. RNAi has generated much excitement as a mechanism of gene regulation and as a laboratory tool for experimental gene silencing. This project will develop an integrated program of research and teaching to understand the natural functions of RNAi during viral infection. In plants and insects, RNAi is a primary antiviral defense response, recognizing and preventing gene expression from harmful nucleic acids. It is likely that RNAi also plays an antiviral role in nematodes. However, because no viruses that are fully infectious in the nematode have been isolated, this speculation has yet to be fully verified. In mammals, there are conflicting views as to whether RNAi functions as an antiviral defense, and this remains a hotly debated topic. Unpublished data from the Sullivan lab shows that viral infection of mammalian cells triggers an innate immune response that inhibits RNAi activity. These data suggest that in contrast to insects and plants, RNAi in mammalian cells is not playing an antiviral role during the early times post-infection. This project will test the model that viral infection of mammalian cells triggers some component of the innate immune response that modifies the RNAi effector machinery (Aim 1); thus, repressing RNAi activity to allow for more robust expression of the protein-based immune response that is unique to higher order vertebrates (Aim 2). In addition, members of the lab will isolate wild nematodes in an effort to identify natural viruses that are fully infectious in the powerful laboratory model nematode C. elegans. These viruses will then be used to fully test the notion that RNAi is an antiviral defense in nematodes (Aim 3). This research will significantly contribute to our understanding of the regulation of the RNAi and cellular host antiviral responses across multiple phyla. The insights gained from this project will be of value to both the basic virology and RNAi fields.
BROADER IMPACTS: The apparently opposite roles RNAi plays in mammalian cells compared to other organisms such as insects (and likely nematodes) represents a marvelous teaching tool for better understanding broad biological concepts such as evolution. The CAREER research activities are integrated within a wider plan for education activities that incorporate cutting edge research opportunities for students in the laboratory, classroom and field: (1) In the laboratory, these goals will be achieved through mentoring graduate, undergraduate, and high school students in hypothesis-driven research projects that span the disciplines of molecular biology, bioinformatics, virology, and RNAi. (2) In the classroom, education and research will be integrated through two very different classes. A completely re-vamped advanced virology undergraduate class has been developed at UT. It focuses on active learning and incorporates the latest molecular techniques and issues of importance to the student demographic (including evolution as a driving force in the "cat and mouse" game of viral interactions with the host). The second course is a component of a 4-week outreach program for 9th graders that participate in the UT Austin University Jumpstart program, and is unique in that these young students participate in a real world science project, with the goal being to isolate the first nematode virus. Studies of wild and laboratory nematodes allow for a cost-effective way to introduce numerous science neophytes to field work, laboratory work, and hypothesis-driven experimentation. The ultimate goal of this course is to discover, culture, and sequence numerous nematode viruses (AKA the "worm virome"), while in the process exposing high school students from underprivileged backgrounds to state-of-the-art laboratory techniques and providing the opportunity to tackle a real world problem in science. It is anticipated that exposing these young students to personal interactions with a university professor will provide inspiration and resources to help foster a future involving college studies in the natural sciences.
