title: Suppression of a dnaKJ deletion by multicopy dksA results from non-feedback-regulated transcripts that originate upstream of the major dksA promoter.
abstract: DksA is an RNA polymerase (RNAP) binding transcription factor that controls expression of a large number of genes in concert with the small-molecule "alarmone" ppGpp. DksA also aids in the resolution of conflicts between RNAP and DNA polymerase (DNAP) during genome replication. DksA was originally identified as a multicopy suppressor of the temperature sensitivity caused by deletion of the genes coding for the DnaKJ chaperone system. Here, we address a longstanding question regarding the role of DksA in ΔdnaKJ suppression. We demonstrate that DksA expression from a multicopy plasmid is necessary and sufficient for suppression, that overexpression occurs despite the fact that the major dksA promoter is feedback regulated in wild-type cells, and that weak, non-feedback-regulated transcription originating upstream of the major promoter for the dksA gene accounts for overexpression. We tentatively rule out three potential explanations for suppression related to known functions of DnaKJ. Because a determinant in DksA needed for the regulation of transcription initiation, but not for resolution of RNAP-DNAP conflicts, is needed to bypass the need for DnaKJ, we suggest that suppression results from an unidentified product whose promoter is directly or indirectly regulated by DksA.
authors.affiliation: Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA.
authors.forename: Pete
authors.initials: P
authors.lastname: Chandrangsu
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Sang Ho
authors.initials: SH
authors.lastname: Choi
authors.forename: Richard L
authors.initials: RL
authors.lastname: Gourse
mesh_terms: D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000378:metabolism; D005246:Feedback; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D050956:HSP40 Heat-Shock Proteins / Q000172:deficiency* / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000172:deficiency* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D013489:Suppression, Genetic; D014158:Transcription, Genetic
chemical_list: C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C090751:dksA protein, E coli; C063842:dnaK protein, E coli