The human REC2/RAD51B gene acts as a DNA damage sensor by inducing G1 delay and hypersensitivity to ultraviolet irradiation

HsRec2/Rad51B is a 350-amino acid protein with a molecular mass of 38,300 Da that appears to be involved in cell cycle regulation and UV-induced apoptosis. The mouse and human genes were isolated based on their homology to a recombinational repair gene from Ustilago maydis and contain functional domains to hRAD51 and hLIM 15 (M. C. Rice et al., Proc. Natl. Acad. Sci. USA, 94: 7417-7422, 1997). Here, we report the results of studies on the behavior of CHO cells containing a plasmid encoding a wild-type hsRec2/Rad51B, a full-length protein with a single mutation at residue 163, which lies in the putative src site, and a truncated version of hsRec2/Rad51B, containing only the first 100 amino acids at the NH2 terminus. Using fluorescence-activated cell sorting analysis to follow the progression of cells through the cell cycle, we find that stable transfectants constitutively overexpressing the wild-type human Rec2/Rad51B protein exhibit a G1 delay. In addition, when irradiated with UV at a dose of 15 J/m2, CHO cells transfected with the various hREC2/RAD51B vectors exhibited different responses. Cells expressing the wild-type human Rec2/Rad51B underwent apoptosis, with the greatest cell death occurring 24 h after irradiation. The control cells, which contained an empty vector, and the cells expressing truncated hsRec2/Rad51B or the full-length Rec2 with a mutation at residue 163 did not. In summary, these findings of cell cycle slowing and UV-induced apoptosis in CHO cells constitutively expressing the human Rec2/Rad51B protein suggest that hsRec2/Rad51B plays a role in a DNA damage surveillance pathway.     

Achievable performance of multivariable systems with unstable zeros and poles

This paper examines the fundamental limitations imposed by unstable (right half plane; RHP) zeros and poles in multivariable feedback systems. We generalize previously known controller-independent lower bounds on the H     

Enabling proteomics discovery through visual analysis

This article presents the motivation for developing visual analysis tools for proteomic data and demonstrates their application to proteomics research with a visualization tool named Peptide Permutation and Protein Prediction, or PQuad, a functioning visual analytic tool for the study of systems biology, is in operation at the Pacific Northwest National Laboratory (PNNL). PQuad supports the exploration of proteins identified by proteomic techniques in the context of supplemental biological information. In particular, PQuad supports differential proteomics by simplifying the comparison of peptide sets from different experimental conditions as well as different proteins identification or confidence scoring techniques. Finally, PQuad supports data validation and quality control by providing a variety of resolutions for huge amounts of data to reveal errors undetected by other methods.     

Enabling proteomics discovery through visual analysis. The peptide permutation and protein prediction tool.

Proteins play a key role in cellular processes, making proteomics central to understanding systems biology. MS techniques provide a means to observe entire proteomes at a global level. Yet, high-throughput MS proteomics techniques generate data faster than it can currently be analyzed. The success of proteomics depends on high-throughput experimental techniques coupled with sophisticated visual analysis and data-mining methods. Visual analysis has been applied successfully in a number of fields plagued with huge, complex data sets and will likely be an important tool in proteomics discovery. PQuad, a novel visualization of MS proteomics data, provides powerful analysis capabilities that support a number of proteomic data applications. In particular, PQuad supports differential proteomics by simplifying the comparison of peptide sets from different experimental conditions as well as different protein identification or confidence scoring techniques. Finally, PQuad supports data validation and quality control by providing a variety of resolutions for huge amounts of data to reveal errors undetected by other methods.     

Tissue specificity of spontaneous point mutations in lambda supF transgenic mice

Abuse of nitrite inhalants, widespread among male homosexuals, has been identified by epidemiological studies as an independent risk factor for AIDS and for Kaposi's sarcoma. Subchronic exposure of mice to inhaled isobutyl nitrite was previously found to impair the tumoricidal activity of peritoneal macrophages. Because inhalants would be expected to have the greatest effects on cells in the lung, alveolar macrophages from exposed mice were examined in this study. Mice were exposed to 900 ppm isobutyl nitrite in an inhalation chamber for 45 min/day for 14 days. Following this treatment, the lungs of exposed mice had large increases in cellularity, both in the alveolar septa and within the alveoli. Bronchoalveolar lavages also contained increased numbers of cells. Alveolar macrophages collected from treated mice had increased tumoricidal activity compared with controls and produced higher levels of inducible nitric oxide and tumor necrosis factor-alpha (TNF-alpha). The frequency of alveolar cells secreting TNF-alpha was increased ninefold in mice exposed to the inhalant. Cell influx into the lung, as indicated by the presence of red blood cells in lung lavages, was evident after only a single 45-min exposure to inhaled isobutyl nitrite at doses as low as 300 ppm.     

Selection of variables for stabilizing control using pole vectors

For a linear multivariable plant, it is known from earlier work that the easy computable pole vectors provide useful information about in which input channel (actuator) a given mode is controllable and in which output channel (sensor) it is observable. In this note, we provide a rigorous theoretical basis for the use of pole vectors, by providing a link to previous results on performance limitations for unstable plants.     

Chromosomal mutations induced by triplex-forming oligonucleotides in mammalian cells

Specific recognition of a region of duplex DNA by triplex-forming oligonucleotides (TFOs) provides an attractive strategy for genetic manipulation. Based on this, we have investigated the ability of the triplex-directed approach to induce mutations at a chromosomal locus in living cells. A mouse fibroblast cell line was constructed containing multiple chromosomal copies of the lambdasupFG1 vector carrying the supFG1 mutation-reporter gene. Cells were treated with specific (psoAG30) or control (psoSCR30) psoralen-conjugated TFOs in the presence and absence of UVA irradiation. The results demonstrated a 6- to 10-fold induction of supFG1 mutations in the psoAG30-treated cells as compared with psoSCR30-treated or untreated control cells. Interestingly, UVA irradiation had no effect onthe mutation frequencies induced by the psoralen-conjugated TFOs, suggesting a triplex-mediated but photoproduct-independent process of mutagenesis. Sequencing data were consistent with this finding since the expected T.A-->A.T transversions at the predicted psoralen crosslinking site were not detected. However, insertions and deletions were detected within the triplex binding site, indicating a TFO-specific induction of mutagenesis. This result demonstrates the ability of triplex-forming oligonucleotides to influence mutation frequencies at a specific site in a mammalian chromosome.     

ThemeRiver: visualizing thematic changes in large documentcollections

The ThemeRiver visualization depicts thematic variations over time within a large collection of documents. The thematic changes are shown in the context of a time-line and corresponding external events. The focus on temporal thematic change within a context framework allows a user to discern patterns that suggest relationships or trends. For example, the sudden change of thematic strength following an external event may indicate a causal relationship. Such patterns are not readily accessible in other visualizations of the data. We use a river metaphor to convey several key notions. The document collection's time-line, selected thematic content and thematic strength are indicated by the river's directed flow, composition and changing width, respectively. The directed flow from left to right is interpreted as movement through time and the horizontal distance between two points on the river defines a time interval. At any point in time, the vertical distance, or width, of the river indicates the collective strength of the selected themes. Colored "currents" flowing within the river represent individual themes. A current's vertical width narrows or broadens to indicate decreases or increases in the strength of the individual theme     

The formation of methyl substituted pyrazines in the Maillard reaction, and the interference by such compounds in the determination of N-nitrosamines in foodstuffs

Summary The formation of methyl substituted pyrazines in the reaction betweenl-alanine andd-glucose (Maillard reaction) is studied and proved by mass spectrometry. These substances interfere strongly in the determination of N-nitrosamines, especially if gas chromatographic and polarographic methods are used. Slight interference may also occur in thin layer chromatography. Colorimetric determination of volatile N-nitrosamines is possible if appropriate clean up procedures are used.

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Zusammenfassung Die Bildung methylsubstituierter Pyrazine bei der Maillard-Reaktion zwischenl-Alanin undd- Glucose wurde untersucht und durch massenspektrometrische Messungen belegt. Die Werte für Pyrazine schwanken sehr stark bei der quantitativen Bestimmung der flüchtigen N-Nitrosamine, besonders wenn gaschromatographische und polarographische Methoden verwendet werden. Geringere Unterschiede werden bei Verwendung dünnschichtchromato-graphischer Methoden beobachtet. Die colorimetrische Bestimmung der Nitrosamine ist dagegen geeignet, wenn spezielle Reinigungsverfahren verwendet werden.

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Abbreviations DMNA dimethyl-N-nitrosamine - DENA diethyl-N-nitrosamine - DPNA dipropyl-N-nitrosamine - DBNA dibutyl-N-nitrosamine - DIBNA diisobutyl-N-nitrosamine Acknowledgement. The authors are deeply indebted to Cand. real. L. Ceh. Department of Biochemistry, The Veterinary College of Norway, Oslo, Norway, to Engineer R. Bosvik, Perkin-Elmer AB, Gotheburg, Sweden and to Docent A. Helgebostad, The Research Station for Furbearing Animals, Heggedal, Norway, for kind and valuable assistance and cooperation in the experiments.