J. Biol. Chem., Vol. 265, Issue 11, 6055-6060, 04, 1990
The RNA antiterminator causes transcription pausing in the leader region of the tryptophan operon
JR Roesser and C Yanofsky
Department of Biological Sciences, Stanford University, California 94305.
In vitro transcription studies with a trp leader DNA template derived from
a double deletion mutant of Serratia marcescens revealed that the
transcription complex pauses synthesis of part of the RNA antiterminator,
structure 2:3. Pausing was enhanced by NusA protein and was dependent on
the concentration of UTP in the transcription reaction mixture. A weak
antiterminator pause also was detected during transcription of the
wild-type S. marcescens trp leader template in the presence of NusA protein
and 1 microM UTP. Transcription pausing following synthesis of the
antiterminator also was observed in a cell- free transcription-translation
system. Antiterminator-induced pausing may play an important role in vivo
by delaying synthesis of RNA segment 4. This delay may influence basal
level control in cells with an excess of tryptophan. In addition, formation
of the antiterminator pause structure may introduce a more stringent
tryptophan starvation requirement for RNA polymerase to read through the
attenuator.