Nanopore molecular trajectories of a eukaryotic reverse transcriptase reveal a long-range RNA structure sensing mechanism

Eukaryotic reverse transcriptases (RTs) can have essential or deleterious roles in normal human physiology and disease. Compared to well-studied helicases, it remains unclear how RTs overcome the ubiquitous RNA structural barriers during reverse transcription. Herein, we describe the development of a Mycobacterium smegmatis porin A (MspA) nanopore technique to sequence RNA to quantify the single-molecule kinetics of an RT from Bombyx mori with single-nucleotide resolution. By establishing a quadromer map that correlates RNA sequence and MspA ion current, we were able to quantify the RT’s dwell time at every single nucleotide step along its RNA template. By challenging the enzyme with various RNA structures, we found that during cDNA synthesis the RT can sense and actively destabilize RNA structures 11–12 nt downstream of its front boundary. The ability to sequence single molecules of RNA with nanopores paves the way to investigate the single-nucleotide activity of other processive RNA translocases.