Volume 272, Number 19,
Issue of May 9, 1997
pp. 12265-12271
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.
NusA Is Required for Ribosomal Antitermination and for Modulation
of the Transcription Elongation Rate of both Antiterminated RNA and
mRNA
(Received for publication, October 11, 1996, and in revised form, February 14, 1997)
Ulla
Vogel
and
Kaj Frank
Jensen
¶
From the 
Department of Biological Chemistry and
¶ Center of Enzyme Research, Institute of Molecular Biology,
University of Copenhagen, Sølvgade 83H, DK-1307
Copenhagen K, Denmark
Ribosomal RNA (rRNA) is elongated twice as fast
as mRNA in vivo due to the presence of antitermination
sequences in the 5
part of the rRNA transcripts. A number of Nus
factors bind to RNA polymerase at the antitermination sites and help
confer resistance to Rho-dependent termination of
transcription. In this paper, the effects of the nusAcs10
allele on the elongation rate of both mRNA and antiterminated RNA
were investigated. The results indicate that NusA is required to
achieve a high elongation rate of RNA chains carrying the ribosomal
antitermination boxA and that antitermination is defective when the
rate of transcription elongation is decreased by the
nusAcs10 allele. Furthermore, the nusAcs10
allele had no significant effects on the elongation rate of normal
lacZ mRNA during steady state growth, but it abolished
the inhibition of lacZ mRNA elongation by guanosine
3,5-bis(diphosphate) (ppGpp). These results suggest that NusA is the
component of the transcription elongation complex required for
inhibition of mRNA elongation by ppGpp.
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