Ribosomal protein S4 is a transcription factor with properties remarkably similar to NusA, a protein involved in both non-ribosomal and ribosomal RNA antitermination

Open Access
Publisher Website
Google Scholar
Abstract
Escherichia coli ribosomal RNA (rRNA) operons contain antitermination motifs necessary for forming terminator‐resistant transcription complexes. In preliminary work, we isolated ‘antiterminating’ transcription complexes and identified four new proteins potentially involved in rRNA transcription antitermination: ribosomal (r‐) proteins S4, L3, L4 and L13. We show here that these r‐proteins and Nus factors lead to an 11‐fold increase in terminator read‐through in in vitro transcription reactions. A significant portion of the effect was a result of r‐protein S4. We show that S4 acted as a general antitermination factor, with properties very similar to NusA. It retarded termination and increased read‐through at Rho‐dependent terminators, even in the absence of the rRNA antiterminator motif. High concentrations of NusG showed reduced antitermination by S4. Like rrn antitermination, S4 selectively antiterminated at Rho‐dependent terminators. Lastly, S4 tightly bound RNA polymerase in vivo. Our results suggest that, like NusA, S4 is a general transcription antitermination factor that associates with RNA polymerase during normal transcription and is also involved in rRNA operon antitermination. A model for key r‐proteins playing a regulatory role in rRNA synthesis is presented.