Poster abstracts

Poster number 73 submitted by Benjamin Warner

A crucial role for the leader-trailer helix and minor role for the antitermination complex in biogenesis of the 30S ribosomal subunit

Benjamin Warner (Department of Microbiology, The Ohio State University), Ralf Bundschuh (Department of Physics, The Ohio State University), Kurt Fredrick (Department of Microbiology, The Ohio State University)

Ribosome biogenesis occurs co-transcriptionally and entails ribosomal (r) RNA folding, r protein binding, rRNA processing, and rRNA modification. In most bacteria, rRNAs are transcribed with tRNAs, and the primary transcript contains leader, trailer, and spacer sequences. Transcription of these long operons involves a modified RNA polymerase, called the antitermination complex, which is recruited by cis-acting RNA elements (boxB, boxA, and boxC) in the leader and spacer regions of the operon. Sequences flanking the rRNAs are complementary and form long helices known as leader-trailer helices. In this work, we interrogate the functional roles of these RNA elements in 30S subunit biogenesis. We find that the structure of the leader-trailer helix is absolutely essential, although its primary sequence can vary. By contrast, loss of boxA only modestly impacts 30S production, indicating a relatively minor role for the antitermination complex. Two adjacent leader helices, termed here hA and hB, are also largely dispensable, consistent with the variable presence of these elements across the Enterobacteriaceae. The fact that the leader-trailer helix is crucial for 30S biogenesis in vivo but unnecessary for efficient reconstitution of the 30S subunits in vitro implies important differences between the two processes.

Keywords: ribosome biogenesis, RNA structure, precursor RNA