title: DNA replication defects in a mutant deficient in the thioredoxin homolog YbbN.
abstract: Escherichia coli contains two thioredoxins, Trx1 and Trx2, and a thioredoxin-like protein, YbbN, that displays both redox and chaperone properties. Since three out of the six proteins of the YbbN interactome (Butland et al., 2005) are components of DNA polymerase 3 holoenzyme (i.e. the β-clamp DnaN, the θ subunit HolE and the δ' subunit HolB), we investigated whether the ybbN mutant presents DNA replication defects. We found that this mutant incorporates (3)H-thymidine at higher rates than the parental strain and displays overinitiation, hypermutator and filamentation phenotypes with the occurrence of anucleated cells. Moreover, YbbN functions as a bona fide chaperone in the refolding of the urea-unfolded β-clamp. These results suggest that the DNA replication and cell division defects of the ybbN mutant might best be explained by chaperone functions of YbbN in the biogenesis of DNA polymerase 3 holoenzyme.
authors.affiliation: Institut Jacques Monod, Université Paris 7, Paris, France.
authors.forename: Hai-Tuong
authors.initials: HT
authors.lastname: Le
authors.forename: Valérie
authors.initials: V
authors.lastname: Gautier
authors.forename: Fatoum
authors.initials: F
authors.lastname: Kthiri
authors.forename: Masamichi
authors.initials: M
authors.lastname: Kohiyama
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Katayama
authors.forename: Gilbert
authors.initials: G
authors.lastname: Richarme
mesh_terms: D004258:DNA Polymerase III / Q000737:chemistry; D004261:DNA Replication / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics*; D005434:Flow Cytometry; D008853:Microscopy; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics*; D009154:Mutation; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000737:chemistry / Q000235:genetics*; D011489:Protein Denaturation; D013879:Thioredoxins / Q000737:chemistry / Q000235:genetics*; D014508:Urea / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D013879:Thioredoxins; D014508:Urea; D050862:Oxidoreductases Acting on Sulfur Group Donors; C510399:YbbN protein, E coli; C101139:beta subunit, DNA polymerase III; D004258:DNA Polymerase III