A high-affinity interaction between NusA and the <i>rrn nut</i> site in <i>Mycobacterium tuberculosis</i>

Abstract

The bacterial NusA protein enhances transcriptional pausing and termination and is known to play an essential role in antitermination. Antitermination is signaled by a nut-like cis-acting RNA sequence comprising boxB, boxA, and boxC. In the present study, we demonstrate a direct, specific high-affinity interaction between the rrn leader nut-like sites and the NusA proteins of Mycobacterium tuberculosis and Escherichia coli. This NusA-RNA interaction relies on the conserved region downstream of boxA, the boxC region, thus demonstrating a key function of this element. We have established an in vivo assay for antitermination in mycobacteria and use this to show that the M. tuberculosis rrn nut-like site enhances transcriptional read-through of untranslated RNA consistent with an antitermination signal within this site. Finally, we present evidence that this NusA-RNA interaction affects transcriptional events further downstream.