Determining if NUS Factors are Essential in Bacteria

Abstract

Escherichia coil, a gram-negative bacterium, has several transcription antitermination proteins or N-utilization substances, Nus. RNA polymerase is modified by the combination of these Nus factors so that transcription may proceed through multiple transcription terminator signals. The Nus proteins include NusA, NusB, NusG and NusE. Classical studies have shown these Nus factors may be important for cell function. This research shows that antitermination of transcription is a basic process of bacterial life and these Nus factors are essential for expression of important genes. Thus the genes add to the minimal set of genes required to support life. Two approaches were used to accomplish this task. First, an experimental detection using recombineering was used to empirically show that Nus factors are essential for bacterial growth. Second using a bioinformatics approach, minimal bacteria genomes were analyzed for the presence of Nus factors and compared with the genomic distribution of the non-essential genes frdA and ibp. Conserved structural motifs were found for the Nus factors. Absolute conservation of Nus factors in minimal genomes strongly predicted their essentiality in bacteria.