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Interrelated effects of DNA supercoiling, ppGpp, and low salt on melting within the Escherichia coli ribosomal RNA rrnB P 1 promoter
Author(s) -
Ohlsen Kari L.,
Gralla Jay D.
Publication year - 1992
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1992.tb01400.x
Subject(s) - dna supercoil , biology , dna , stringent response , rna , plasmid , escherichia coli , ribosomal rna , in vivo , microbiology and biotechnology , biophysics , biochemistry , genetics , gene , dna replication
Summary The formation of complexes containing high levels of DNA melting at the ribosomal RNA rrnB P1 promoter in vitro is shown to be facilitated by DNA supercoiling or low salt. The effector nucleotide ppGpp is ineffective under these conditions. The loss of supercoils or addition of salt increases the effectiveness of ppGpp in inhibiting formation of these complexes. In vivo plasmid DNA supercoiling is shown to decrease during starvation protocols that also increase levels of ppGpp. The results suggest that ppGpp regulation may be affected by the state of DNA supercoiling in vivo.