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Articles by J Bergeron
Total Records ( 2 ) for J Bergeron
  D Lu , S Fillet , C Meng , Y Alguel , P Kloppsteck , J Bergeron , T Krell , M. T Gallegos , J Ramos and X. Zhang

The majority of bacterial gene regulators bind as symmetric dimers to palindromic DNA operators of 12–20 base pairs (bp). Multimeric forms of proteins, including tetramers, are able to recognize longer operator sequences in a cooperative manner, although how this is achieved is not well understood due to the lack of complete structural information. Models, instead of structures, of complete tetrameric assembly on DNA exist in literature. Here we present the crystal structures of the multidrug-binding protein TtgV, a gene repressor that controls efflux pumps, alone and in complex with a 42-bp DNA operator containing two TtgV recognition sites at 2.9 Å and 3.4 Å resolution. These structures represent the first full-length functional tetrameric protein in complex with its intact DNA operator containing two continuous recognition sites. TtgV binds to its DNA operator as a highly asymmetric tetramer and induces considerable distortions in the DNA, resulting in a 60° bend. Upon binding to its operator, TtgV undergoes large conformational changes at the monomeric, dimeric, and tetrameric levels. The structures here reveal a general model for cooperative DNA binding of tetrameric gene regulators and provide a structural basis for a large body of biochemical data and a reinterpretation of previous models for tetrameric gene regulators derived from partial structural data.

  S Paglialunga , P Julien , Y Tahiri , F Cadelis , J Bergeron , D Gaudet and K. Cianflone

Acylation stimulating protein (ASP, C3adesArg) is an adipose tissue derived hormone that stimulates triglyceride (TG) synthesis. ASP stimulates lipoprotein lipase (LPL) activity by relieving feedback inhibition caused by fatty acids (FA). The present study examines plasma ASP and lipids in male and female LPL-deficient subjects primarily with the P207L mutation, common in the population of Quebec, Canada. We evaluated the fasting and postprandial states of LPL heterozygotes and fasting levels in LPL homozygotes. Homozygotes displayed increased ASP (58–175% increase, P < 0.05–0.01), reduced HDL-cholesterol (64–75% decrease, P < 0.0001), and elevated levels of TG (19–38-fold, P < 0.0001) versus control (CTL) subjects. LPL heterozygotes with normal fasting TG (1.3–1.9 mmol/l) displayed increased ASP (101–137% increase, P < 0.05–0.01) and delayed TG clearance after a fatload; glucose levels remained similar to controls. Hypertriglyceridemics with no known LPL mutation also had increased ASP levels (63–192% increase, P < 0.001). High-TG LPL heterozygotes were administered a fatload before and after fibrate treatment. The treatment reduced fasting and postprandial plasma ASP, TG, and FA levels without changing insulin or glucose levels. ASP enhances adipose tissue fatty-acid trapping following a meal; however in LPL deficiency, high ASP levels are coupled with delayed lipid clearance.

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