Molecular interaction between COP1 and HY5 defines a regulatory switch for light control of Arabidopsis development

Arabidopsis COP1 acts as a light-inactivable repressor of photomorphogenic development, but its molecular mode of action remains unclear. Here, we show that COP1 negatively regulates HY5, a bZIP protein and a positive regulator of photomorphogenic development. Both in vitro and in vivo assays indicate that COP1 interacts directly and specifically with HY5. The hyperphotomorphogenic phenotype caused by the over-expression of a mutant HY5, which lacks the COP1-interactive domain, supports the regulatory role of HY5-COP1 interaction. Further, HY5 is capable of directly interacting with the CHS1 minimal promoter and is essential for its light activation. We propose that the direct interaction with and regulation of transcription factors by COP1 may represent the molecular mechanism for its control of gene expression and photomorphogenic development.

Arabidopsis bZIP protein HY5 directly interacts with light-responsive promoters in mediating light control of gene expression

The Arabidopsis HY5 gene has been defined genetically as a positive regulator of photomorphogenesis and recently has been shown to encode a basic leucine zipper type of transcription factor. Here, we report that HY5 is constitutively nuclear localized and is involved in light regulation of transcriptional activity of the promoters containing the G-box, a well-characterized light-responsive element (LRE). In vitro DNA binding studies suggested that HY5 can bind specifically to the G-box DNA sequences but not to any of the other LREs present in the light-responsive promoters examined. High-irradiance light activation of two synthetic promoters containing either the consensus G-box alone or the G-box combined with the GATA motif (another LRE) and the native Arabidopsis ribulose bisphosphate carboxylase small subunit gene RBCS-1A promoter, which has an essential copy of the G-box, was significantly compromised in the hy5 mutant. The hy5 mutation's effect on the high-irradiance light activation of gene expression was observed in both photosynthetic and nonphotosynthetic tissues. Furthermore, the characteristic phytochrome-mediated red light- and far-red light-reversible low-fluence induction of the G-box-containing promoters was diminished specifically in hy5 plants. These results suggest that HY5 may interact directly with the G-box in the promoters of light-inducible genes to mediate light-controlled transcriptional activity.

The molecular basis of allorecognition

Until recently it was generally assumed that the focus of T cell receptor recognition of allogeneic MHC molecules was the polymorphic regions on the molecule that differed between responder and stimulator. It is now clear that all T cell recognition, including self-tolerance and allorecognition, involves both the MHC molecule and its associated peptide ligand. Polymorphic residues located within the peptide binding groove of the MHC and inaccessible to the T cell receptor can profoundly affect selection and recognition of bound peptides. These peptide differences between histoincompatible individuals greatly amplify the antigenic impact of MHC polymorphism and result in the high frequency of alloreactive cells. Evidence for the role of peptides in allorecognition is reviewed.

Free radical scavenging behavior of folic acid: evidence for possible antioxidant activity

The free radical scavenging properties and possible antioxidant activity of folic acid are reported. Pulse radiolysis technique is employed to study the one-electron oxidation of folic acid in homogeneous aqueous solution. The radicals used for this study are CCl(3)O(2)(*), N(3)(*), SO(4)(*-), Br(2)(*-), *OH, and O(*-). All these radicals react with folic acid under ambient condition at an almost diffusion-controlled rate producing two types of transients. The first transient absorption maximum is around 430 nm, which decays, and a simultaneous growth at around 390 nm is observed. Considering the chemical structure of folic acid, the absorption maximum at 430 nm has been assigned to a phenoxyl radical. The latter one is proposed to be a delocalized molecular radical. A permanent product has been observed in the oxidation of folic acid with CCl(3)O(2)(*) and N(3)(*) radicals, with a broad absorption band around 370-400 nm. The bimolecular rate constants for all the radical-induced oxidation reactions of folic acid have been measured. Folic acid is seen to scavenge these radicals very efficiently. In the reaction of thiyl radicals with folic acid, it has been observed that folic acid can not only scavenge thiyl radicals but can also repair these thiols at physiological pH. While carrying out the lipid peroxidation study, in spite of the fact that folic acid is considerably soluble in water, we observed a significant inhibition property in microsomal lipid peroxidation. A suitable mechanism for oxidation of folic acid and repair of thiyl radicals by folic acid has been proposed.

Generation of femtosecond pulses of synchrotron radiation

Femtosecond synchrotron pulses were generated directly from an electron storage ring. An ultrashort laser pulse was used to modulate the energy of electrons within a 100-femtosecond slice of the stored 30-picosecond electron bunch. The energy-modulated electrons were spatially separated from the long bunch and used to generate approximately 300-femtosecond synchrotron pulses at a bend-magnet beamline, with a spectral range from infrared to x-ray wavelengths. The same technique can be used to generate approximately 100-femtosecond x-ray pulses of substantially higher flux and brightness with an undulator. Such synchrotron-based femtosecond x-ray sources offer the possibility of applying x-ray techniques on an ultrafast time scale to investigate structural dynamics in condensed matter.

High-molecular-weight RNAs of AKR, NZB, and wild mouse viruses and avian reticuloendotheliosis virus all have similar dimer structures

Several 50 to 70S tumor viral RNAs have previously been shown by electron microscopy to be dimers, with the two monomer subunits joined near their 5' ends. Five additional naturally occurring type C RNA tumor viruses have now been examined: AKR, and endogenous murine ecotropic virus; NZB, an endogenous murine xenotropic virus; and ecotropic and an amphotropic virus isolated from a wild mouse; and the avian reticuloendotheliosis virus (REV). All five 50 to 70S RNAs have similar 5'-to-5' dimer structures. Therefore, the observations support the hypothesis that the dimer linkage is a structural feature common to all type C mammalian viruses. REV is the first example of an avian virus with a clear 5'-to 5' dimer linkage. All of the mammalian viral RNAs, but not REV, showed symmetrically placed loops in each subunit of the dimer. Possible molecular structures and biological functions of the dimer linkages and loops are discussed.

Control of V(D)J recombinational accessibility of the D beta 1 gene segment at the TCR beta locus by a germline promoter

The germline promoter region upstream of the D beta 1 gene segment in the murine TCR beta locus was deleted to assess its role in controlling V(D)J recombination. Associated with diminished D beta 1 region germline transcription, rearrangement of the D beta 1 but not the D beta 2 gene segment was reduced 10- to 20-fold. A corresponding reduction in RAG-mediated cleavage at the D beta 1 and J beta 1 signal sequences was apparent only when purified CD4- CD8- thymocytes were analyzed because, as we demonstrate, cleavage at these gene segments also occurred in CD4+ CD8+ thymocytes. These findings suggest that germline promoters regulate localized accessibility of gene segments for recombination and that in CD4+ CD8+ thymocytes TCR beta allelic exclusion does not result from inaccessibility of D beta gene segments.

Uteroglobin: a novel cytokine?

Blastokinin or uteroglobin (UG) is a steroid-inducible, evolutionarily conserved, multifunctional protein secreted by the mucosal epithelial of virtually all mammals. It is present in the blood and in other body fluids including urine. An antigen immunoreactive to UG antibody is also detectable in the mucosal epithelia of all vertebrates. UG-binding proteins (putative receptor), expressed on several normal and cancer cell types, have been characterized. The human UG gene is mapped to chromosome 11q12.2 13.1, a region that is frequently rearranged or deleted in many cancers. The generation of UG knockout mice revealed that disruption of this gene causes: (i) severe renal disease due to an abnormal deposition of fibronectin and collagen in the glomeruli; (ii) predisposition to a high incidence of malignancies; and (iii) a lack of polychlorinated biphenyl binding and increased oxygen toxicity in the lungs. The mechanism(s) of UG action is likely to be even more complex as it also functions via a putative receptor-mediated pathway that has not yet been clearly defined. Molecular characterization of the UG receptor and signal transduction via this receptor pathway may show that this protein belongs to a novel cytokine/chemokine family.

Pathology of aging B6;129 mice

Fifty male and 49 female B6;129 mice (wild-type, +/+) were maintained until 2 years of age to study their age-related pathology. By 104-105 weeks, 14/50 (28%) of the males and 30/49 (61%) of the females were still alive. The most common contributing cause of morbidity or mortality was lymphoma. Lymphoma was observed in 21/50 (42%) of the males and 33/49 (67%) of the females with the most common sites being mesenteric lymph nodes, gut associated lymphoid tissue (Peyer's patches), and spleen. The lymphoma most often appeared to arise in the mesenteric node. Immunohistochemistry revealed CD45R expression as well as infiltration by many CD3+ T cells. IgH gene rearrangements were found in typical mesenteric node lymphomas indicating B-cell origin. They bore similarities to the human T-cell rich, B-cell lymphomas. Other tumors included hepatocellular adenoma or carcinoma (male 12%, females 10%), lung alveolar Type II cell adenoma or carcinoma (male 32%, female 20%), thyroid follicular adenoma or carcinoma (male 2%, female 8%), ovarian tumors (17%), and endometrial tumors (6%). Nonneoplastic lesions included amyloid-like material in the nasal septum (male and female 100%), otitis media (male 84%, female 79%), epididymal epithelial karyomegaly (88%), melanosis (high incidences in various tissues including brain, parathyroid, and spleen), membranoproliferative glomerulonephritis (male 52%, female 71%), hyalinosis with extracellular crystals in several tissues (respiratory tract, gall bladder, stomach), islet cell hyperplasia (male 45%, female 29%) and esophageal dilation (male 10%, female 6%). The B6;129 mouse is a mouse with aging lesions similar to those in other mouse strains but with a characteristic common lymphoma.

Bipartite function of a small RNA hairpin in transcription antitermination in bacteriophage lambda

Transcription of downstream genes in the early operons of phage lambda requires a promoter-proximal element known as nut. This site acts in cis in the form of RNA to assemble a transcription antitermination complex which is composed of lambda N protein and at least four host factors. The nut-site RNA contains a small stem-loop structure called boxB. Here, we show that boxB RNA binds to N protein with high affinity and specificity. While N binding is confined to the 5' subdomain of the stem-loop, specific N recognition relies on both an intact stem-loop structure and two critical nucleotides in the pentamer loop. Substitutions of these nucleotides affect both N binding and antitermination. Remarkably, substitutions of other loop nucleotides also diminish antitermination in vivo, yet they have no detectable effect on N binding in vitro. These 3' loop mutants fail to support antitermination in a minimal system with RNA polymerase (RNAP), N, and the host factor NusA. Furthermore, the ability of NusA to stimulate the formation of the RNAP-boxB-N complex is diminished with these mutants. Hence, we suggest that boxB RNA performs two critical functions in antitermination. First, boxB binds to N and secures it near RNAP to enhance their interaction, presumably by increasing the local concentration of N. Second, boxB cooperates with NusA, most likely to bring N and RNAP in close contact and transform RNAP to the termination-resistant state.

Mechanisms of curcumin-induced apoptosis of Ehrlich's ascites carcinoma cells

Curcumin, the active ingredient from the spice turmeric (Curcuma longa Linn), is a potent antioxidant and anti-inflammatory agent. It has been recently demonstrated to possess discrete chemopreventive activities. However, the molecular mechanisms underlying such anticancer properties of curcumin still remain unrealized, although it has been postulated that induction of apoptosis in cancer cells might be a probable explanation. In the current study, curcumin was found to decrease the Ehrlich's ascites carcinoma (EAC) cell number by the induction of apoptosis in the tumor cells as evident from flow-cytometric analysis of cell cycle phase distribution of nuclear DNA and oligonucleosomal fragmentation. Probing further into the molecular signals leading to apoptosis of EAC cells, we observed that curcumin is causing tumor cell death by the up-regulation of the proto-oncoprotein Bax, release of cytochrome c from the mitochondria, and activation of caspase-3. The status of Bcl-2 remains unchanged in EAC, which would signify that curcumin is bypassing the Bcl-2 checkpoint and overriding its protective effect on apoptosis.

Elliptic flow of charged particles in Pb-Pb collisions at sqrt[S(NN)] = 2.76 TeV

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at sqrt[S(NN)] =2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (|η|<0.8) and transverse momentum range 0.2<p t<5.0 GeV/c. The elliptic flow signal v₂, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 ± 0.002(stat) ± 0.003(syst) in the 40%-50% centrality class. The differential elliptic flow v₂ p t reaches a maximum of 0.2 near p t =3 GeV/c. Compared to RHIC Au-Au collisions at sqrt[S(NN)] 200 GeV, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.

MKP1/CL100 controls tumor growth and sensitivity to cisplatin in non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) represents the most frequent and therapy-refractive sub-class of lung cancer. Improving apoptosis induction in NSCLC represents a logical way forward in treating this tumor. Cisplatin, a commonly used therapeutic agent in NSCLC, induces activation of N-terminal-c-Jun kinase (JNK) that, in turn, mediates induction of apoptosis. In analysing surgical tissue samples of NSCLC, we found that expression of MKP1/CL100, a negative regulator of JNK, showed a strong nuclear staining for tumor cells, whereas, in normal bronchial epithelia, MKP1 was localized in the cytoplasm as well as in nuclei. In the NSCLC-derived cell lines H-460 and H-23, we found that MKP1 was constitutively expressed. Expressing a small-interfering RNA (siRNA) vector for MKP1 in H-460 cells resulted in a more efficient activation by cisplatin of JNK and p38 than in the parental cells, and this correlated with a 10-fold increase in sensitivity to cisplatin. A similar response was also observed in H-460 and H-23 cells when treated with the MKP1 expression inhibitor RO-31-8220. Moreover, expression of a siRNA-MKP2, an MKP1-related phosphatase, had no effect on H-460 cell viability response to cisplatin. Tumors induced by H-460 cells expressing MKP1 siRNA grew slower in nu(-)/nu(-) mice and showed more susceptibility to cisplatin than parental cells, and resulted in an impaired growth of the tumor in mice. On the other hand, overexpression of MKP1 in the H-1299 NSCLC-derived cell line resulted in further resistance to cisplatin. Overall, the results showed that inhibition of MKP1 expression contributes to a slow down in cell growth in mice and an increase of cisplatin-induced cell death in NSCLC. As such, MKP1 can be an attractive target in sensitizing cells to cisplatin to increase the effectiveness of the drug in treating NSCLC.

In vitro protein folding by ribosomes from Escherichia coli, wheat germ and rat liver: the role of the 50S particle and its 23S rRNA

Ribosomes from a number of prokaryotic and eukaryotic sources (e.g. Escherichia coli, wheat germ and rat liver) can refold a number of enzymes which are denatured with guanidine/HC1 prior to incubation with ribosomes. In this report, we present our observations on the refolding of denatured lactate dehydrogenase from rabbit muscle and glucose-6-phosphate dehydrogenase from baker's yeast by ribosomes from E. coli, wheat germ and rat liver. The protein-folding activity of E. coli ribosomes was found to be present in 50S particles and in 23S rRNA. The 30S particle or 16S rRNA did not show any protein-folding activity. The protein-folding activity of 23S rRNA may depend on its tertiary conformation. Loss of tertiary structure, by incubation with low concentrations of EDTA, inhibited the protein-folding activity of 23S rRNA. This low concentration of EDTA had no effect on folding of the denatured enzymes by themselves.

Combinatorial interaction of light-responsive elements plays a critical role in determining the response characteristics of light-regulated promoters in Arabidopsis

We have studied the roles of PhyA, PhyB and CRY1 photoreceptors and the downstream light-signaling components, COP1 and DET1, in mediating high-irradiance light-controlled activity of promoters containing synthetic light-responsive elements (LRE). Promoters with paired LREs were able to respond to a wide spectrum of light through multiple photoreceptors, while the light-inducible single LRE promoters primarily responded to a specific wavelength of light. In addition, our results indicate that Cry1 is involved in PhyB-mediated red-light induction of the G-GATA/NOS101 promoter, and that both Cry1 and PhyB are required for effective repression of the GT1/NOS101 promoter by red or blue light. An interaction between PhyA and PhyB in mediating GT1-GATA/NOS101 promoter light activation was also observed. Furthermore, our data indicate that COP1 and DET1 exert negative control in the dark only on paired LRE promoters but not single LRE promoters. From these results, we conclude that the combinatorial interaction of LREs is essential in determining the ability of light-responsive promoters to be modulated by crucial cellular regulators and to respond to diverse light environments.

Inflammation-induced ROS generation causes pancreatic cell death through modulation of Nrf2/NF-κB and SAPK/JNK pathway

Chronic pancreatitis is characterized by progressive loss of exocrine and endocrine functions of the pancreas and is considered to be the single most important cause for development of pancreatic cancer. Recent evidence suggests that inflammation and oxidative stress play pivotal roles in the development of clinical conditions like pancreatitis, type 2 diabetes mellitus, and metabolic syndrome. Nonetheless, molecular signaling pathways linking inflammation, oxidative stress, and pancreatic cell death are not yet well defined. In this study, bacterial lipopolysaccharide (LPS) was used (injected twice a week for three weeks) to emulate a chronic systemic inflammatory state in experimental Swiss albino mice. Using this model, we traced the genesis of inflammation-induced pancreatic dysfunction and mapped the signaling events which contribute to the induction of this state. Histopathological studies revealed the appearance of cell injuries and increased collagen content in LPS-exposed group, indicative of fibrosis. Assays for intraperitoneal glucose tolerance, insulin levels, and insulin receptor mRNA expression signified inflammation-induced insulin insensitivity. For the first time we present evidence that cellular inflammation and subsequent oxidative stress modulate the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)/NF-E2-related factor 2 or Nuclear factor (erythroid-derived 2)-like 2 pathway and initiates pancreatic cell death by activation of stress-responsive Rho/stress-activated protein kinase or SAPK/Jun-N-terminal kinase (JNK) pathway. Scavenging of intracellular reactive oxygen species (ROS) by a standard antioxidant N-acetyl cysteine led to pancreatic cell survival. The data obtained strongly indicates that the LPS/toll-like receptor-4 or TLR-4/ROS/NF-κB pathway is critically involved in the initiation of inflammation, oxidative stress, and pancreatic cell death and might prove to be an excellent choice as a target for novel therapeutic strategies in the management of metabolic disorders.

Transverse-momentum and collision-energy dependence of high-pT hadron suppression in Au+Au collisions at ultrarelativistic energies

We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at sqrt[s(NN)]=200 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5<p(T)<12 GeV/c. The collision energy dependence of the yields and the centrality and p(T) dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. We observe no evidence of p(T)-dependent suppression, which may be expected from models incorporating jet attenuation in cold nuclear matter or scattering of fragmentation hadrons.