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Histone-like Protein HU and Bacterial DNA Topology: Suppression of an HU Deficiency by Gyrase Mutations
Ist Teil von
Journal of molecular biology, 1996-02, Vol.256 (1), p.66-76
Ort / Verlag
England: Elsevier Ltd
Erscheinungsjahr
1996
Link zum Volltext
Quelle
Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
Beschreibungen/Notizen
The abundant bacterial protein called HU has the ability to wrap and bend DNA
in vitro, and thus it has long been thought to play a role in DNA supercoiling. In the absence of HU,
Escherichia coliformed tiny colonies on agar, rapidly accumulated suppressor mutations, and was hypersensitive to novobiocin. |vertsb|Three types of evidence implicated gyrase in the suppression of an HU deficiency. First, spontaneous suppressors that restored normal growth and reduced sensitivity to novobiocin mapped in
gyrB, one of the genes encoding DNA gyrase. Second, a pair of known
gyrBmutations (gyrB-203 Ts
gyrB-221Nov
R|1ru|) allowed normal growth at permissive (30°C) but not at intermediate (37°C) conditions. Third, introduction of a
gyrB-expressing plasmid restored normal colony size. DNA supercoiling comparisons showed that chromosomal supercoiling decreased in the absence of HU and increased toward wild-type levels in the presence of a spontaneous
gyrBsuppressor. Taken together, these data establish that HU has a physiological role in chromosomal DNA topology, probably by facilitating the action of gyrase.