title: Global Transcriptional Regulation of Backbone Genes in Broad-Host-Range Plasmid RA3 from the IncU Group Involves Segregation Protein KorB (ParB Family).
abstract: The KorB protein of the broad-host-range conjugative plasmid RA3 from the IncU group belongs to the ParB family of plasmid and chromosomal segregation proteins. As a partitioning DNA-binding factor, KorB specifically recognizes a 16-bp palindrome which is an essential motif in the centromere-like sequence parSRA3, forms a segrosome, and together with its partner IncC (ParA family) participates in active DNA segregation ensuring stable plasmid maintenance. Here we show that by binding to this palindromic sequence, KorB also acts as a repressor for the adjacent mobC promoter driving expression of the mobC-nicoperon, which is involved in DNA processing during conjugation. Three other promoters, one buried in the conjugative transfer module and two divergent promoters located at the border between the replication and stability regions, are regulated by KorB binding to additional KorB operators (OBs). KorB acts as a repressor at a distance, binding to OBs separated from their cognate promoters by between 46 and 1,317 nucleotides. This repressor activity is facilitated by KorB spreading along DNA, since a polymerization-deficient KorB variant with its dimerization and DNA-binding abilities intact is inactive in transcriptional repression. KorB may act as a global regulator of RA3 plasmid functions in Escherichia coli, since its overexpression in transnegatively interferes with mini-RA3 replication and stable maintenance of RA3.
authors: Institute of Biochemistry and Biophysics, Department of Microbial Biochemistry, Polish Academy of Sciences, Warsaw, Poland akulinska@ch.pw.edu.pl.|Warsaw University of Technology, Faculty of Chemistry, Institute of Biotechnology, Warsaw, Poland.
authors: Anna
authors: A
authors: Kulinska
authors: Institute of Biochemistry and Biophysics, Department of Microbial Biochemistry, Polish Academy of Sciences, Warsaw, Poland.|Warsaw University of Life Sciences, Faculty of Human Nutrition and Consumer Sciences, Laboratory of Food Chemistry, Warsaw, Poland.
authors: Jolanta
authors: J
authors: Godziszewska
authors: Institute of Biochemistry and Biophysics, Department of Microbial Biochemistry, Polish Academy of Sciences, Warsaw, Poland.|Warsaw University of Technology, Faculty of Chemistry, Institute of Biotechnology, Warsaw, Poland.
authors: Anna
authors: A
authors: Wojciechowska
authors: Institute of Biochemistry and Biophysics, Department of Microbial Biochemistry, Polish Academy of Sciences, Warsaw, Poland.
authors: Marta
authors: M
authors: Ludwiczak
authors: Institute of Biochemistry and Biophysics, Department of Microbial Biochemistry, Polish Academy of Sciences, Warsaw, Poland.
authors: Grazyna
authors: G
authors: Jagura-Burdzy
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins