Crystallization and diffraction analysis of thioredoxin reductase from Streptomyces coelicolor

Thioredoxin reductases are homodimeric flavoenzymes that catalyze the transfer of electrons from NADPH to oxidized thioredoxin substrate. Bacterial thioredoxin reductases represent a promising target for the development of new antibiotics. Recombinant thioredoxin reductase TrxB from Streptomyces coelicolor was crystallized using the hanging-drop vapour-diffusion method. X-­ray diffraction data were collected from cryocooled crystals to 2.4 Å resolution using a synchrotron-radiation source. The crystals belonged to the primitive monoclinic space group P2(1), with unit-cell parameters a = 82.9, b = 60.6, c = 135.4 Å, α = γ = 90.0, β = 96.5°

Evidence for a protective role of the STAT5 transcription factor against oxidative stress in human leukemic pre-B cells

International audienceSTAT5 transcription factors are involved in normal B lymphocyte development and in leukemogenesis. We show that the inhibition of STAT5A expression or activity in the NALM6, 697 and Reh leukemic pre-B cell lines, results in a higher spontaneous apoptosis and an increased FAS-induced cell death. However, the molecular mechanisms underlying the altered pre-B cell survival are unclear. We used a proteomic approach to identify proteins that are differentially regulated in cells expressing (NALM6Δ5A) or not a dominant negative form of STAT5A. Among the 14 proteins identified, six were involved in the control of the oxidative stress like glutathione (GSH) synthetase and DJ-1. Accordingly, we showed increased levels of reactive oxygen species (ROS) in NALM6Δ5A cells and suppression of the increased sensitivity to Fas-mediated apoptosis by the GSH tripeptide. Similar results were observed when NALM6 cells were treated with TAT-STAT5Δ5A fusion proteins or STAT5A shRNA. In addition, the 697 and Reh pre-B cells were found to share number of molecular changes observed in NALM6Δ5A cells including ROS generation, following inhibition of STAT5 expression or function. Our results point out to a hitherto undescribed link between STAT5 and oxidative stress and provide new insights into STAT5 functions and their roles in leukemogenesis