As an approach to understanding how mammals regulate H 2 O 2 intracellular concentration to prevent its toxicity, we analyzed the genome-wide mRNA profile changes of human cells after treatment with a non-toxic H 2 O 2 concentration. We identified a large and essentially late H 2 O 2 response of induced and repressed genes that unexpectedly comprise few or no antioxidants but mostly apoptosis and cell cycle control activities. The requirement of the p53 regulator for regulating about a third of this H 2 O 2 stimulon and the lack of an associated enhancement of total cellular H 2 O 2 scavenging activity further suggest that H 2 O 2 elicits a stress antiproliferative/repair response that does not increase antioxidant defenses. We conclude that mammalian antioxidant defenses are constitutive, a finding that contrasts with the oxidant-inducibility of such defenses in microorganisms. This finding might be important in understanding the role of H 2 O 2 as a key signaling molecule in mammals.Oxygen is both essential for aerobic life, because it is the terminal electron acceptor in respiration, and dangerous, because of the potency of reactive oxygen species (ROS) 1 to indiscriminately oxidize biological molecules. ROS include the superoxide anion (O 2 . ) and hydrogen peroxide (H 2 O 2 ). Antioxidant systems that avert ROS toxicity comprise the scavenging enzymes superoxide dismutase, catalase, selenothiol-and thiolperoxidase, as well as associated electron donor systems that include the pentose phosphate, thioredoxin, and glutathione pathways (1-3). In microorganisms, antioxidant systems are part of so-called oxidative stress-inducible adaptive responses (1, 2, 4). Specialized regulators operate these responses by sensing minimal increases in ROS concentration and setting the transcriptional expression of oxidant scavenger genes in proportion. Such regulation, meant to prevent oxidative stressinduced cellular damage, is essential for the aerobic life of microorganisms and has the hallmarks of a homeostatic control. It is not clearly established, however, whether similar ROS-inducible genetic responses exist in mammals. This question is highly significant because, in addition to their toxic side, ROS have been attributed specific roles in mammalian signal transduction. H 2 O 2 , especially, acts as a key signaling molecule in cell growth and differentiation (5, 6), and many eukaryotic signaling pathways, by being redox-sensitive, could be influenced by ROS (7-9). The identification of mammalian ROS sensors should be an indication of the existence of ROS-inducible responses. However, as of today, no such function has been precisely identified in mammals. The Keap1-Nrf2 system senses electrophiles and controls the expression of phase II detoxifying enzymes through the antioxidant/electrophile response element (10 -12), but it has no demonstrated direct role in ROS sensing per se (13,14). Similarly, several stress-responsive regulators, including the c-Jun N-terminal kinase stressactivated mitogen activated protein kina...

A eDNA clone (HUT2) sharing 61.1% and 89.9% sequence identity with the human erythroid (HUTll) and the rabbit (UT2) urea transporters, respectively, was isolated by homology cloning from a human kidney library. HUT2 transcripts were restricted to the kidney and the HUT2 polypeptide was not immunoprecipitated with blood group Kidd-related antibodies (anti-Jk3) in coupled transcriptiontranslation assays. Functional expression studies in Xenopus oocytes demonstrated that HUT2-mediated urea transport was not inhibited by p-chloromercuribenzene sulfonate (pCMBS) which, however, inhibited the urea flux mediated by HUTll. These findings demonstrate that at least two distinct urea transporters are present in human tissues. By in situ hybridization, the gene encoding HUT2 has been assigned to chromosome 18q12.l-q21-1, as found previously for the Kidd/urea transporter HUT11, suggesting that both genes evolved from duplication of a common ancestor.

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Despite its importance during viral or bacterial infections, transcriptional regulation of the interferon-β gene (Ifnb1) in activated macrophages is only partially understood. Here we report that TRIM33 deficiency results in high, sustained expression of Ifnb1 at late stages of toll-like receptor-mediated activation in macrophages but not in fibroblasts. In macrophages, TRIM33 is recruited by PU.1 to a conserved region, the Ifnb1 Control Element (ICE), located 15 kb upstream of the Ifnb1 transcription start site. ICE constitutively interacts with Ifnb1 through a TRIM33-independent chromatin loop. At late phases of lipopolysaccharide activation of macrophages, TRIM33 is bound to ICE, regulates Ifnb1 enhanceosome loading, controls Ifnb1 chromatin structure and represses Ifnb1 gene transcription by preventing recruitment of CBP/p300. These results characterize a previously unknown mechanism of macrophage-specific regulation of Ifnb1 transcription whereby TRIM33 is critical for Ifnb1 gene transcription shutdown.

The Kidd (JK) blood group locus encodes a urea transporter that is expressed on human red cells and on endothelial cells of the vasa recta in the kidney. Here, we report the identification in human erythroblasts of a novel cDNA, designated HUT11A, which encodes a protein identical to the previously reported erythroid HUT11 urea transporter, except for a Lys 44 3 Glu substitution and a Val-Gly dipeptide deletion after proline 227, which leads to a polypeptide of 389 residues versus 391 in HUT11. Genomic typing by polymerase chain reaction and transcript analysis by ribonuclease protection assay demonstrated that HUT11A encodes the true Kidd blood group/urea transporter protein, which carries only 2 Val-Gly motifs. Upon expression at high levels in Xenopus oocytes, the physiological Kidd/urea transporter HUT11A conferred a rapid transfer of urea (which was insensitive to p-chloromercuribenzene sulfonate or phloretin), a high water permeability, and a selective uptake of small solutes including amides and diols, but not glycerol and meso-erythritol. However, at plasma membrane expression levels close to the level observed in the red cell membrane, HUT11A-mediated water transport and small solutes uptake were absent and the urea transport was poorly inhibited by p-chloromercuribenzene sulfonate, but strongly inhibited by phloretin. These findings show that, at physiological expression levels, the HUT11A transporter confers urea permeability but not water permeability, and that the observed water permeability is a feature of the red cell urea transporter when expressed at unphysiological high levels.

A set of B-cell activation molecules, including the Epstein-Barr virus (EBV) receptor CR2 (CD21) and the B-cell activation antigen CD23 (Blast2/Fc epsilon RII), is turned on by infecting EBV-negative B-lymphoma cell lines with immortalizing strains of the viruslike B95-8 (BL/B95 cells). This up regulation may represent one of the mechanisms involved in EBV-mediated B-cell immortalization. The P3HR1 nonimmortalizing strain of the virus, which is deleted for the entire Epstein-Barr nuclear antigen 2 (EBNA2) protein open reading frame, is incapable of inducing the expression of CR2 and CD23, suggesting a crucial role for EBNA2 in the activation of these molecules. In addition, lymphoma cells containing the P3HR1 genome (BL/P3HR1 cells) do not express the viral latent membrane protein (LMP), which is regularly expressed in cells infected with immortalizing viral strains. Using electroporation, we have transfected the EBNA2 gene cloned in an episomal vector into BL/P3HR1 cells and have obtained cell clones that stably express the EBNA2 protein. In these clones, EBNA2 expression was associated with an increased amount of CR2 and CD23 steady-state RNAs. Of the three species of CD23 mRNAs described, the Fc epsilon RIIa species was preferentially expressed in these EBNA2-expressing clones. An increased cell surface expression of CR2 but not of CD23 was observed, and the soluble form of CD23 molecule (SCD23) was released. We were, however, not able to detect any expression of LMP in these cell clones. These data demonstrate that EBNA2 gene is able to complement P3HR1 virus latent functions to induce the activation of CR2 and CD23 expression, and they emphasize the role of EBNA2 protein in the modulation of cellular gene implicated in B-cell proliferation and hence in EBV-mediated B-cell immortalization. Nevertheless, EBNA2 expression in BL/P3HR1 cells is not able to restore the level of CR2 and CD23 expression observed in BL/B95 cells, suggesting that other cellular or viral proteins may also have an important role in the activation of these molecules: the viral LMP seems to be a good candidate.

The PNS described could help in the diagnosis and follow-up of UCNT patients because they may be the first manifestation of the disease or may reappear with relapse. BMI is a frequent finding in patients with metastases and is unrelated to PNS.

Bone marrow-derived macrophages (BMDM) are primary macrophages obtained by in vitro differentiation of bone marrow cells in the presence of macrophage colony-stimulating factor (M-CSF or CSF1). They are easy to obtain in high yields, can be stored by freezing, and can be obtained from genetically modified mice strains. They are therefore widely used as prototypical macrophages for in vitro studies. In this chapter, we present the method for obtaining BMDMs and freezing them.