Purification of a glucose-binding protein from rat liver nuclei. Evidence for a role in targeting of nuclear mRNP to nuclear pore complex.

A nuclear carbohydrate-binding protein with a molecular mass of 67 kDa (CBP67), which is specific for glucose residues, was purified to essential homogeneity from rat liver nuclear extracts. This protein could also be isolated from nuclear ribonucleoprotein (RNP) complexes by extraction in the presence of 0.6 M or 2 M NaCl, but it was absent in polysomal RNP complex. The binding of the purified protein, which has an isoelectric point of 7.3, to glucose-containing glycoconjugates depends on the presence of Ca2+ and Mg2+. Using closed nuclear envelope vesicles as a system to study nuclear transport of RNA, it was shown that both entrapped polysomal mRNA and nuclear RNA precursors are readily exported from the vesicles in an ATP-dependent manner. The transport was unidirectional and strongly promoted by the poly(A) segment attached to these RNAs. In contrast, nuclear RNP complexes entrapped into the vesicles together with glucose-conjugated bovine serum albumin or nucleoplasmin, or bird nest glycoprotein, were not exported into the extravesicular space. However, transport of nuclear RNP complexes could be achieved in the presence of glucose or after co-addition of a glucose-recognizing lectin from Pellina semitubulosa. In Western blots, radioiodinated CBP67 binds to an 80-kDa polypeptide both in isolated rat liver nuclear envelopes and pore-complex laminae. From these results we postulate that CBP67 may direct nuclear RNP complexes to the nuclear pore.     

A significant strain difference in "biochemical aging" of rats

We have measured the time course of induction of glucokinase in response to glucose refeeding following a fast. Old Charles River males (Sprague-Dawley) show a significantly greater lag before initiation of enzyme induction than do Wistar males of the same age. Female Wistar rats show no age dependent decrement in responsiveness between 4 and 14 months of age.     

Kombinierte elektronenmikroskopische Darstellung der Arylsulfatase und der sauren Phosphatase in Lysosomen des Nierentubulus

Zusammenfassung Durch Doppelinkubation ist es möglich, Aktivitäten der Arylsulfatase und der sauren Phosphatase in ein und derselben Gewebsprobe elektronenmikroskopisch zu lokalisieren. Wie Kontrollversuche zeigen, wird weder das bei der ersten Inkubation entstandene Reaktionsprodukt durch das zweite Medium, noch die Aktivität des an zweiter Stelle dargestellten Enzyms durch die vorausgehende Einwirkung des ersten Mediums merkbar verändert.Untersucht wurden Epithelien aus dem proximalen Tubuluskonvolut der Rattenniere. Die nach konventioneller Darstellung der Arylsulfatase und der sauren Phosphatase auftretenden Reaktionsprodukte unterscheiden sich sowohl morphologisch als auch durch ihre Beugungseigenschaften. Anhand der letzteren können sie als Bariumsulfat und Bleiphosphat identifiziert werden.Nach der Doppelinkubation beobachtet man manchmal beide Reaktionsprodukte in einem Lysosom, möglicherweise seltener als es den wirklichen Verhältnissen entspricht; denn an den mit dem ersten Reaktionsprodukt besetzten Stellen kann die zweite Reaktion vermutlich nicht mehr stattfinden. Außerdem kommen nebeneinander Lysosomen mit Bariumsulfat- und solche mit Bleiphosphatniederschlägen vor. Da methodische Einflüsse diesen Befund nicht ausreichend erklären können, muß angenommen werden, daß es innerhalb einer Zelle enzymatisch heterogene Lysosomen gibt.Die Methode erscheint geeignet, ein kompletteres Spektrum der Lysosomen einer Zelle cytochemisch zu erfassen, als es bisher möglich gewesen ist.

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Combined electronmicroscopical localization of aryl sulfatase and acid phosphatase activities within lysosomes of kidney tubule cells

Summary A cytochemical method is reported permitting the eleotronmicroscopical localization of both aryl sulfatase and acid phosphatase within the same specimen by a double incubation. Control essays demonstrate, that neither the first reaction product is altered by the second medium, nor the activity of the second enzyme by the first medium.Epithelial cells of the proximal convoluted tubule of rat kidney were examined. The reaction products after simple aryl sulfatase and acid phosphatase staining differ in their morphology as well as in their diffraction pattern. By the aid of the latter they are shown to be barium sulfate and lead phosphate, as expected.After double incubation on the one hand the two reaction products are found within a single lysosom, but probably less frequently than it would correspond to the original enzyme activities; for it must be expected that the second reaction is impossible in places already occupied by the first reaction product. On the other hand one observes lysosomes containing only barium sulfate or lead phosphate. Methodical influences may not explain such differences, and it is believed, therefore, that enzymical heterogenous lysosomes exist within the same cell.The proposed method seems to be suitable to visualize a more complete spectrum of lysosomes than the methods hitherto existing.

     

TOPP--the OpenMS proteomics pipeline

MOTIVATION: Experimental techniques in proteomics have seen rapid development over the last few years. Volume and complexity of the data have both been growing at a similar rate. Accordingly, data management and analysis are one of the major challenges in proteomics. Flexible algorithms are required to handle changing experimental setups and to assist in developing and validating new methods. In order to facilitate these studies, it would be desirable to have a flexible 'toolbox' of versatile and user-friendly applications allowing for rapid construction of computational workflows in proteomics. RESULTS: We describe a set of tools for proteomics data analysis-TOPP, The OpenMS Proteomics Pipeline. TOPP provides a set of computational tools which can be easily combined into analysis pipelines even by non-experts and can be used in proteomics workflows. These applications range from useful utilities (file format conversion, peak picking) over wrapper applications for known applications (e.g. Mascot) to completely new algorithmic techniques for data reduction and data analysis. We anticipate that TOPP will greatly facilitate rapid prototyping of proteomics data evaluation pipelines. As such, we describe the basic concepts and the current abilities of TOPP and illustrate these concepts in the context of two example applications: the identification of peptides from a raw dataset through database search and the complex analysis of a standard addition experiment for the absolute quantitation of biomarkers. The latter example demonstrates TOPP's ability to construct flexible analysis pipelines in support of complex experimental setups. AVAILABILITY: The TOPP components are available as open-source software under the lesser GNU public license (LGPL). Source code is available from the project website at www.OpenMS.de     

Transfer of the UAP56 interaction motif of human cytomegalovirus pUL69 to its murine cytomegalovirus homolog converts the protein into a functional mRNA export factor that can substitute for pUL69 during viral infection

Nucleocytoplasmic shuttling and interaction with the cellular mRNA export factor UAP56 are prerequisites for the mRNA export activity of human cytomegalovirus (HCMV) pUL69. Although the murine cytomegalovirus homolog pM69 shuttles, it fails to export mRNAs due to its inability to recruit UAP56. However, chimeric proteins comprising pM69 fused to N-terminal pUL69 fragments, including its UAP56 interaction motif, acquire mRNA export activity. Importantly, growth curves of recombinant HCMVs illustrate that such a chimeric protein, but not pM69, substitutes for pUL69 during HCMV infection.