Binding of the Heterogeneous Ribonucleoprotein K (hnRNP K) to the Epstein-Barr Virus Nuclear Antigen 2 (EBNA2) Enhances Viral LMP2A Expression

The Epstein-Barr Virus (EBV) -encoded EBNA2 protein, which is essential for the in vitro transformation of B-lymphocytes, interferes with cellular processes by binding to proteins via conserved sequence motifs. Its Arginine-Glycine (RG) repeat element contains either symmetrically or asymmetrically di-methylated arginine residues (SDMA and ADMA, respectively). EBNA2 binds via its SDMA-modified RG-repeat to the survival motor neurons protein (SMN) and via the ADMA-RG-repeat to the NP9 protein of the human endogenous retrovirus K (HERV-K (HML-2) Type 1). The hypothesis of this work was that the methylated RG-repeat mimics an epitope shared with cellular proteins that is used for interaction with target structures. With monoclonal antibodies against the modified RG-repeat, we indeed identified cellular homologues that apparently have the same surface structure as methylated EBNA2. With the SDMA-specific antibodies, we precipitated the Sm protein D3 (SmD3) which, like EBNA2, binds via its SDMA-modified RG-repeat to SMN. With the ADMA-specific antibodies, we precipitated the heterogeneous ribonucleoprotein K (hnRNP K). Specific binding of the ADMA- antibody to hnRNP K was demonstrated using E. coli expressed/ADMA-methylated hnRNP K. In addition, we show that EBNA2 and hnRNP K form a complex in EBV- infected B-cells. Finally, hnRNP K, when co-expressed with EBNA2, strongly enhances viral latent membrane protein 2A (LMP2A) expression by an unknown mechanism as we did not detect a direct association of hnRNP K with DNA-bound EBNA2 in gel shift experiments. Our data support the notion that the methylated surface of EBNA2 mimics the surface structure of cellular proteins to interfere with or co-opt their functional properties.     

Rethinking the relationship between nestedness and beta diversity: a comment on Baselga (2010)

Baselga [Partitioning the turnover and nestedness components of beta diversity. Global Ecology and Biogeography, 19 , 134–143, 2010] proposed pairwise (β_nes) and multiple‐site (β_NES) beta‐diversity measures to account for the nestedness component of beta diversity. We used empirical, randomly created and idealized matrices to show that both measures are only partially related to nestedness and do not fit certain fundamental requirements for consideration as true nestedness‐resultant dissimilarity measures. Both β_nes and β_NES are influenced by matrix size and fill, and increase or decrease even when nestedness remains constant. Additionally, we demonstrate that β_NES can yield high values even for matrices with no nestedness. We conclude that β_nes and β_NES are not true measures of the nestedness‐resultant dissimilarity between sites. Actually, they quantify how differences in species richness that are not due to species replacement contribute to patterns of beta diversity. Finally, because nestedness is a special case of dissimilarity in species composition due to ordered species loss (or gain), the extent to which differences in species composition is due to nestedness can be measured through an index of nestedness.     

Re-evaluation of the prospects of marker-assisted selection for improving insect resistance against Diatraea spp. in tropical maize by cross validation and independent validation

Cross validation (CV) and validation with an independent sample (IV) are new biometric approaches in QTL analysis to obtain unbiased estimates of QTL effects and the proportion of the genetic variance explained by the detected marker-QTL association (p). Our objective with these methods was to obtain a realistic picture on the prospects of marker-assisted selection (MAS) for improving the resistance of maize against the tropical stem borer species Diatraea grandiosella (SWCB) and Diatraea saccharalis (SCB). Published QTL mapping studies on leaf-damage ratings (LDR) with populations of F_2:3 lines and recombinant inbred lines (RIL) from crosses CML131×CML67 and Ki3× CML139 of tropical maize inbreds were re-analyzed with CV and IV. With CV, the reduction in p for LDR compared to p obtained with the whole data set varied between 41.0 and 79.6% in the populations of F_2:3 lines and between 30.1 and 65.2% in the two populations of RIL. Estimates of p for SCB LDR were similar for CV and IV. For SWCB LDR, p estimates obtained with IV were larger than those obtained with CV in CML131× CML67. The reverse was observed for Ki3×CML139. Under the assumption of identical selection intensities, and based on the re-estimates of p, MAS using only molecular marker information is less-efficient than conventional phenotypic selection (CPS). MAS combining marker and phenotypic data increases the relative efficiency by only 4% in comparison to CPS. In conclusion, MAS for improving SWCB and SCB LDR seems not-promising unless additional QTLs with proven large effects are available or the costs of marker assays are considerably reduced. Received: 7 December 2000 / Accepted: 5 February 2001     

The effect of prior exercise on ex vivo induction of heme oxygenase-1 in human lymphocytes

It was postulated that prior demanding exercise would suppress the induction of the oxidant-responsive protein Heme Oxygenase-1 (HO-1) in mononuclear cells following subsequent ex vivo H₂O₂ treatment. Eight male subjects completed two trials in a randomized order (one rest and one exercise) and ex vivo HO-1 protein induction was determined following H₂O₂ treatment in lymphocytes and monocytes before and after each trial using a newly developed and reproducible assay. Lymphocytes obtained 2 h post-exercise showed a modest reduction in HO-1 protein expression in response to ex vivo treatment with H₂O₂ (p<0.05). The plasma concentration of the HO-1 suppressor α1-antitrypsin increased immediately post-exercise (p<0.05) and it is tentatively suggested that this may explain the modest transient reduction in ex vivo HO-1 protein induction in lymphocytes in response to an independent oxidant challenge following a prior bout of demanding exercise.     

Sphingosine-1-Phosphate Induces Dose-Dependent Chemotaxis or Fugetaxis of T-ALL Blasts through S1P1 Activation

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid involved in several physiological processes including cell migration and differentiation. S1P signaling is mediated through five G protein-coupled receptors (S1P1-S1P5). S1P1 is crucial to the exit of T-lymphocytes from the thymus and peripheral lymphoid organs through a gradient of S1P. We have previously observed that T-ALL and T-LBL blasts express S1P1. Herein we analyzed the role of S1P receptors in the migratory pattern of human T-cell neoplastic blasts. S1P-triggered cell migration was directly related to S1P1 expression. T-ALL blasts expressing low levels of S1P1 mRNA (HPB-ALL) did not migrate toward S1P, whereas those expressing higher levels of S1P1 (MOLT-4, JURKAT and CEM) did migrate. The S1P ligand induced T-ALL cells chemotaxis in concentrations up to 500 nM and induced fugetaxis in higher concentrations (1000–10000 nM) through interactions with S1P1. When S1P1 was specifically blocked by the W146 compound, S1P-induced migration at lower concentrations was reduced, whereas higher concentrations induced cell migration. Furthermore, we observed that S1P/S1P1 interactions induced ERK and AKT phosphorylation, and modulation of Rac1 activity. Responding T-ALL blasts also expressed S1P3 mRNA but blockage of this receptor did not modify migratory responses. Our results indicate that S1P is involved in the migration of T-ALL/LBL blasts, which is dependent on S1P1 expression. Moreover, S1P concentrations in the given microenvironment might induce dose-dependent chemotaxis or fugetaxis of T-ALL blasts.     

Effect of short- and medium-term toxicity of doxorubicin on spermatogenesis in adult Wistar rats

Doxorubicin (DXR) is a widely used chemotherapeutic anticancer agent that has potent activity against several solid and non-solid human malignant tumors, including childhood malignancies. However, DXR has serious toxic effects on tissues with rapid cell cycles, such as myeloid and lymphatic tissues, intestinal mucosa, testes and ovaries. In the present study, the short- and medium-term toxic effects of DXR on the reproductive system of male Wistar rats were evaluated using morphometric and stereological tools to quantify damage to the seminiferous epithelium. Adult male Wistar rats were treated with dose of 7.5?mg/kg of DXR and were sacrificed at seven, 14, 21 and 28?days after treatment. The testes were fixed in glutaraldehyde solution, routinely processed and embedded in plastic for evaluation under a light microscope. A significant reduction in testis weight was found as a result of massive germ cell apoptosis. Differences in comparison to the control group were found in the relative frequency of all stages of the seminiferous epithelium cycle, with significant differences for stages VIII–XI. Apoptosis significantly decreased the number of pachytene spermatocytes in the stages evaluated (I, II–III and VIII) at seven and 14?days. At 21 and 28?days after treatment, the testes exhibited the massive loss of germ cells that resulted in a missing cell layer. Moreover, reductions in the height of seminiferous tubules, tubular diameter and tubular compartment as well as an increase in the intertubular compartment were found in the period studied.