Directed Evolution of an Epitranscriptomic Toolkit

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PROJECT SUMMARY/ABSTRACT The post-transcriptional modification of RNA is critical for RNA stability, trafficking, and translation into proteins. In humans, disruption of the most prevalent RNA modification, N6-methyladenosine (m6A), has been linked to diseases such as cancer. To better understand the role of m6A in disease pathogenesis, biologists require robust methods for mapping m6A sites within RNA. Despite recent progress, existing methods require numerous steps, lack selectivity and sensitivity, or demonstrate sequence bias. The long-term goal of this project is to address these limitations by developing enzymes that can detect m6A and applying these tools for epitranscriptomic analysis of cancer cells. Two strategies will be pursued in parallel: 1) Evolve reverse- transcriptases, which polymerize DNA using RNA as a template, to incorporate a nucleotide “marker” into DNA at m6A sites during reverse transcription of cellular RNA. This would facilitate direct readout of m6A without the requirement for antibody-based pulldowns. 2) Engineer deaminases to mark m6A sites. Adenine deaminases convert adenine (A) to inosine (I), which is read as guanine (G) by polymerases. Thus, engineering deaminases to selectively deaminate m6A, rather than A, would result in a mark that can be located by RNA sequencing. Finally, the evolved reverse transcriptase and deaminase platforms will be thoroughly biochemically characterized and implemented for m6A sequencing of mammalian cells to establish the proposed platform. The development and dissemination of these tools will have a broad impact by facilitating studies of m6A and its role in human health.