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Transcription antitermination in an Escherichia coli haemolysin operon is directed progressively by cis ‐acting DNA sequences upstream of the promoter region
Author(s) -
Koronakis V.,
Cross M.,
Hughes C.
Publication year - 1989
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.1365-2958.1989.tb00122.x
Subject(s) - operon , antitermination , biology , terminator (solar) , transcription (linguistics) , l arabinose operon , escherichia coli , gal operon , genetics , gene , lac operon , dna , trp operon , primer extension , microbiology and biotechnology , promoter , structural gene , rna , gene expression , ionosphere , linguistics , philosophy , physics , astronomy
Summary Export of haemolysin protein (HlyA) directed by the Escherichia coli pHly152 hly determinant is dependent upon transcriptional activation, primarily strong intra‐operon transcript antitermination imposed between the haemolysin structural genes hlyC and hlyA and the contiguous downstream export genes hlyB and hlyD . Transcript elongation was dictated by a DNA sequence several kb upstream of the rho‐independent terminator but could not be assigned to a discrete locus; on the contrary, it was progressive, increasing with the addition of up to 3.5kbp of operon‐proximal sequence containing the insertion elements IS2 and IS91. Antitermination was prominent throughout logarithmic growth but absent in stationary phase, and was effective only in cis but not in trans . Primer extension indicated that transcription activation utilized the native transcriptional start sites of the unactivated hly operon.