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Journal of Bacteriology, March 2004, p. 1304-1310, Vol. 186, No. 5
0021-9193/04/$08.00+0 DOI: 10.1128/JB.186.5.1304-1310.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
King Faisal Specialist Hospital and Research Centre, Radiation Biology Laboratory, Biomedical Physics Department, Riyadh 11211, Saudi Arabia,1 Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111,2 Department of Biology, Georgia State University, Atlanta, Georgia 303033
Received 29 August 2003/ Accepted 24 November 2003
Similarities between lambda and rRNA transcription antitermination have led to suggestions that they involve the same Nus factors. However, direct in vivo confirmation that rRNA antitermination requires all of the lambda Nus factors is lacking. We have therefore analyzed the in vivo role of NusB and NusG in rRNA transcription antitermination and have established that both are essential for it. We used a plasmid test system in which reporter gene mRNA was measured to monitor rRNA antiterminator-dependent bypass of a Rho-dependent terminator. A comparison of terminator read-through in a wild-type Escherichia coli strain and that in a nusB::IS10 mutant strain determined the requirement for NusB. In the absence of NusB, antiterminator-dependent terminator read-through was not detected, showing that NusB is necessary for rRNA transcription antitermination. The requirement for NusG was determined by comparing rRNA antiterminator-dependent terminator read-through in a strain overexpressing NusG with that in a strain depleted of NusG. In NusG-depleted cells, termination levels were unchanged in the presence or absence of the antiterminator, demonstrating that NusG, like NusB, is necessary for rRNA transcription antitermination. These results imply that NusB and NusG are likely to be part of an RNA-protein complex formed with RNA polymerase during transcription of the rRNA antiterminator sequences that is required for rRNA antiterminator-dependent terminator read-through.
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