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Characterization of BK Polyomaviruses from Kidney Transplant Recipients Suggests a Role for APOBEC3 in Driving In-Host Virus Evolution

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Human-Specific Adaptations in Vpu Conferring Anti-tetherin Activity Are Critical for Efficient Early HIV-1 Replication In Vivo

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Human endogenous retrovirus K10: expression of Gag protein and detection of antibodies in patients with seminomas.

The human endogenous retrovirus K10 (HERV-K10) has been identified in the human genome by its homology to retroviruses of other vertebrates (M. Ono, T. Yasunaga, T. Miyata, and H. Ushikubo, J. Virol. 60:589-598, 1986). Using PCR amplification, DNA cloning, sequencing, and procaryotic expression, we were able to demonstrate that HERV-K10 encodes a 73-kDa protein which was processed by a HERV-K10-encoded protease to yield proteins p22/p26, p30, and p15/16. Analysis of the teratocarcinoma cell line Tera 1 or tumor tissues by immunoblotting demonstrated that the 80-kDa polyprotein of HERV-K10 gag and a processed protein of 39 kDa were expressed. In addition, a major protein of 39 kDa and additional species of 30, 22, 19, and 17 kDa could be detected in the supernatant of Tera 1 cells, suggesting that HERV-K10 Gag proteins are either secreted or processed to probably incomplete viral particles. In addition, the gag gene of HERV-K10 was expressed in the baculovirus system. Using this recombinant system to test antisera from patients with different diseases and healthy individuals, we were able to detect antibodies against the N-terminal part of HERV-K10 Gag in 2 to 4% of groups of tumor patients with titers ranging between 1:80 and 1:640, while approximately 0.1 to 0.5% of healthy individuals exhibited antibodies with lower titers. In contrast, patients with seminoma had antibody titers in the range of 1:2,560 at the time when the tumor was detected. Immunohistochemistry using specific rabbit sera or monoclonal antibodies against HERV-K10 Gag revealed that the Gag protein is expressed in the cytoplasm of the tumor cells. Furthermore, an 80-kDa protein corresponding to the HERV-K10 Gag polyprotein could be detected in tumor biopsies. For the first time, these data indicate that HERV-K10 Gag proteins are synthesized in seminoma cells and tumors exhibit relatively high antibody titers against Gag. So far, no information on which role HERV-K10 plays in the development of this tumor exists.     

Starch metabolism in poplar wood ray cells during spring mobilization and summer deposition

Treatment with cyclohexylamine, an inhibitor of spermidine synthase, accelerated radicle emergence in chick-pea ( Cicer arietinum L. cv. Castellana) seeds. Stimulation in the growth of embryonic axis was correlated with: (a) a rise in putrescine (Put) and cadaverine (Cad); (b) a decrease in spermidine (Spd) and spermine (Spm), and (c) a concomitant acceleration of the transformation from S-adenosylmethionine (SAM) into ethylene with increases in the levels of l-aminocyclopropane-l-carboxylic acid (ACC), l-(malonylamino)cyclopropane-l-carboxylic acid (mACC) and ethylene and ACC synthase and ethylene-forming enzyme activities. Cyclohexylamine also stimulated the mitotic index in both apical and subapical zones of the radicle and the apical zone of the plumule. The sectional distribution of the ethylene pathway and polyamine content was studied in embryonic axes of seeds germinated for 65 h. Each axis was divided into 5 sections: radicle meristem, elongation zone, differentiation zone, hypocotyl and plumule. In the presence of cyclohexylamine, ACC synthase and ACC were strongly stimulated in both the differentiation and hypocotyl zones, whereas the mACC was stimulated in all sections of the embryonic axis. With respect to ethylene-forming enzyme activity and ethylene production, the hypocotyl and the zones of elongation and differentiation were affected most by cyclohexylamine. Cyclohexylamine also induced an accumulation of free Put and Spm in the differentiation, hypocotyl and radicle zones, whereas Put and Spm bound to small substances increased most in the hypocotyl and plumule. The Spd bound to small substances decreased in all sections in the presence of cyclohexylamine. With respect to polyamines bound to macromolecules, cyclohexylamine stimulated only the accumulation of Put since Spd and Spm were strongly inhibited in all sections.     

A Highly Conserved Residue of the HIV-1 gp120 Inner Domain Is Important for Antibody-Dependent Cellular Cytotoxicity Responses Mediated by Anti-cluster A Antibodies

Previous studies have shown that sera from HIV-1-infected individuals contain antibodies able to mediate antibody-dependent cellular cytotoxicity (ADCC). These antibodies preferentially recognize envelope glycoprotein (Env) epitopes induced upon CD4 binding. Here, we show that a highly conserved tryptophan at position 69 of the gp120 inner domain is important for ADCC mediated by anti-cluster A antibodies and sera from HIV-1-infected individuals.     

Changes in carbohydrates and ultrastructure in xylem ray cells ofPopulus in response to chilling

Summary The ultrastructure of xylem ray cells inPopulus was studied in conjunction with their content of individual sugars and of starch. They differ considerably in structure and in carbohydrate content at the three chosen stages,i.e., of starch deposition (August), of starch maximum (November), and of starch dissolution (January). The transition from the summer to winter stage was also induced experimentally by storage of tissue at 0°C. Both in nature and after cold-storage, sucrose and its galactosides raffinose and stachyose were accumulated to a great extent, contributing up to 69.7 and 57.3% of total sugar content, respectively. They originated parallel to the breakdown of starch and to the appearance of abundant vesicular and dilated ER cisternae. Results indicating that they are the specific sites of sucrose accumulation, and/or its galactosides, are discussed. The occurrence of phytoferritin-like crystalloids in amyloplasts and of vacuolar flocculent material, which condenses into electron-dense bodies of suspectedly proteinaceous nature, is described.Dedicated to Professor Dr. Wilhelm Halbsguth on the occasion of his 75th birthday.     

Protein bodies in ray cells of Populus x canadensis Moench ‘robusta’

Light- and electron-microscopical investigations revealed distinct intravacuolar protein aggregates of 0.3–0.8 m in diameter in ray cells of poplar during the dormant season. In semi-thin sections, these bodies showed positive protein staining and enzymatic digestibility with pepsin, indicating their proteinaceous nature. Morphometric measurements showed such protein bodies in 7–13% of the area of the ray-cell lumen. This amount corresponded with the protein content of the wood determined biochemically, e.g. 2.0–5.0 g·mg^-1 dry weight. Polyacrylamide gel electrophoresis of the total protein fraction extracted from wood showed prominent polypeptide species with an apparent molecular weight of 30–32 kilodaltons. The results indicate considerable protein storage in ray cells, especially in the form of protein-storage vacuoles.Abbreviation DW dry weight