title: SuhB Associates with Nus Factors To Facilitate 30S Ribosome Biogenesis in Escherichia coli.
abstract: A complex of highly conserved proteins consisting of NusB, NusE, NusA, and NusG is required for robust expression of rRNA in Escherichia coli. This complex is proposed to prevent Rho-dependent transcription termination by a process known as "antitermination." The mechanism of this antitermination in rRNA is poorly understood but requires association of NusB and NusE with a specific RNA sequence in rRNA known as BoxA. Here, we identify a novel member of the rRNA antitermination machinery: the inositol monophosphatase SuhB. We show that SuhB associates with elongating RNA polymerase (RNAP) at rRNA in a NusB-dependent manner. Although we show that SuhB is required for BoxA-mediated antitermination in a reporter system, our data indicate that the major function of the NusB/E/A/G/SuhB complex is not to prevent Rho-dependent termination of rRNA but rather to promote correct rRNA maturation. This occurs through formation of a SuhB-mediated loop between NusB/E/BoxA and RNAP/NusA/G. Thus, we have reassigned the function of these proteins at rRNA and identified another key player in this complex.
  
  
  OBJECTIVE
  As RNA polymerase transcribes the rRNA operons in E. coli, it complexes with a set of proteins called Nus that confer enhanced rates of transcription elongation, correct folding of rRNA, and rRNA assembly with ribosomal proteins to generate a fully functional ribosome. Four Nus proteins were previously known, NusA, NusB, NusE, and NusG; here, we discover and describe a fifth, SuhB, that is an essential component of this complex. We demonstrate that the main function of this SuhB-containing complex is not to prevent premature transcription termination within the rRNA operon, as had been long claimed, but to enable rRNA maturation and a functional ribosome fully competent for translation.
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA.
authors.forename: Navjot
authors.initials: N
authors.lastname: Singh
authors.affiliation: Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Bubunenko
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA.
authors.forename: Carol
authors.initials: C
authors.lastname: Smith
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Abbott
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Stringer
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA.
authors.forename: Ronald
authors.initials: R
authors.lastname: Shi
authors.affiliation: Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
authors.forename: Donald L
authors.initials: DL
authors.lastname: Court
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York, USA Department of Biomedical Sciences, University at Albany, Albany, New York, USA joseph.wade@health.ny.gov.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Wade
mesh_terms: D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D012323:RNA Processing, Post-Transcriptional; D012335:RNA, Ribosomal / Q000378:metabolism*; D054680:Ribosome Subunits, Small, Bacterial / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D012335:RNA, Ribosomal; D012321:DNA-Directed RNA Polymerases; D010744:Phosphoric Monoester Hydrolases; C000612346:SuhB protein, E coli; C021822:myo-inositol-1 (or 4)-monophosphatase