J. Biol. Chem., Vol. 262, Issue 9, 3940-3943, Mar, 1987
Stringent control in Escherichia coli applies also to transcription by T7 RNA polymerase
M Yamagishi, JR Cole, M Nomura, FW Studier and JJ Dunn
During amino acid starvation the synthesis of rRNA and tRNA is specifically
inhibited (stringently controlled) in wild type Escherichia coli but not in
relaxed strains carrying the relA mutation. We have found that the in vivo
transcription of a hybrid rrnB rRNA operon, in which the normal promoter
region has been replaced by the lambda PL promoter, is under stringent
control even though this promoter lacks the "stringent discriminator"
sequence postulated to be required for stringent control. Furthermore, we
have found that transcription of the rrnB operon from a phage T7 promoter,
as well as T7 genes in general, by phage T7 RNA polymerase is also subject
to stringent control in vivo. These results are consistent with the idea
that stringent control acts in a relatively nonspecific manner to inhibit
some step(s) in transcription that are often rate-limiting for very active
transcription. The relative simplicity of transcription by phage T7 RNA
polymerase should offer a good system to study the molecular mechanisms of
stringent control.