The 9 A resolution cryo-electron microscopy map of Sindbis virus presented here provides structural information on the polypeptide topology of the E2 protein, on the interactions between the E1 and E2 glycoproteins in the formation of a heterodimer, on the difference in conformation of the two types of trimeric spikes, on the interaction between the transmembrane helices of the E1 and E2 proteins, and on the conformational changes that occur when fusing with a host cell. The positions of various markers on the E2 protein established the approximate topology of the E2 structure. The largest conformational differences between the icosahedral surface spikes at icosahedral 3-fold and quasi-3-fold positions are associated with the monomers closest to the 5-fold axes. The long E2 monomers, containing the cell receptor recognition motif at their extremities, are shown to rotate by about 180 degrees and to move away from the center of the spikes during fusion.

The adenovirus type 5 (Ad5) early 1B 55-kDa protein (E1B-55kDa) is a multifunctional phosphoprotein that regulates viral DNA replication and nucleocytoplasmic RNA transport in lytically infected cells. In addition, E1B-55kDa provides functions required for complete oncogenic transformation of rodent cells in cooperation with the E1A proteins. Using the far-Western technique, we have isolated human genes encoding E1B-55kDa-associated proteins (E1B-APs). The E1B-AP5 gene encodes a novel nuclear RNA-binding protein of the heterogeneous nuclear ribonucleoprotein (hnRNP) family that is highly related to hnRNP-U/SAF-A. Immunoprecipitation experiments indicate that two distinct segments in the 55-kDa polypeptide which partly overlap regions responsible for p53 binding are required for complex formation with E1B-AP5 in Ad-infected cells and that this protein interaction is modulated by the adenovirus E4orf6 protein. Expression of E1B-AP5 efficiently interferes with Ad5 E1A/E1B-mediated transformation of primary rat cells. Furthermore, stable expression of E1B-AP5 in Ad-infected cells overcomes the E1B-dependent inhibition of cytoplasmic host mRNA accumulation. These data suggest that E1B-AP5 might play a role in RNA transport and that this function is modulated by E1B-55kDa in Ad-infected cells.

Interleukin-1 (IL-1) 1 possesses a wide spectrum of inflammatory, metabolic, physiological, hematopoetic, and immunological properties. IL-1 binds to two different receptors of the Ig superfamily: IL-1 receptor type I (IL-1RI) and IL-1 receptor type II (IL-1RII). Both receptors bind the ligands with distinct affinities (1). Whereas IL-1RI is necessary for signal transduction (2), IL-1RII is not capable of transducing an activation signal but rather acts as a decoy receptor serving as a ligand sink and competing for IL-1 with the IL-1RI (3-5). An additional member of the IL-1 receptor family, IL-1 receptor accessory protein (IL-1RAcP), has also been identified. The 66-kDa IL-1RAcP shares limited homology with IL-1RI and IL-1RII but does not bind IL-1 (6). It has been shown that co-expression of the IL-1RAcP is essential for a fully functional IL-1RI complex (7-10).In the last years the elucidation of early IL-1 signaling events has progressed. After ligand-induced complex formation of IL-1RI and IL-1RAcP (7-11), the Ser/Thr kinase IRAK is recruited to the receptor complex, where it becomes highly phosphorylated (12, 13). Recruitment of IRAK requires the intracellular domains of both receptor chains (8,10,14). Dominant-negative forms of MyD88 block IL-1 signaling (15). After phosphorylation by itself (12) or by additional kinases (16), IRAK leaves the receptor complex and interacts with tumor necrosis factor receptor-associated factor 6 (17). Recently, the MAP kinase kinase kinase TAK1 has been identified to interact with tumor necrosis factor receptor-associated factor 6 in association with , thereby providing a link to the machinery that activates nuclear factor B (NF-B) via stimulation of IB kinases (IKK␣ and IKK␤) (23-28). One critical component in the signaling cascade is MyD88 (29, 30), because mice lacking this adaptor molecule do not show cytokine-induced activation of NF-B and c-Jun N-terminal kinase (JNK) (31).We have previously described an IL-1RI-positive subclone of EL4 cells, EL4D6/76, which binds IL-1 with high affinity but fails to activate NF-B or produce IL-2 following IL-1 stimulation (7,32). This defect is due to the lack of IL-1RAcP expression and can be overcome by transfection with IL-1RAcP, thus reconstituting IL-1-specific functional defects in EL4D6/76 cells (7,9). In the present study we investigated regions within the cytoplasmic domain of IL-1RAcP that are required for perpetuating IL-1 responses. We present data demonstrating that, in addition to box 3 (aa 538 -542) of the TIR domain, aa 527-534 within the cytoplasmic domain of IL-1RAcP are essential for IL-1 signaling. EXPERIMENTAL PROCEDURES Construction of Truncated and Mutated Forms of IL-1RAcP-Trun-cated forms of IL-1RAcP were constructed by PCR technique. The vector pEF-IL-1RAcP containing the murine IL-1RAcP coding sequence was used as a template (9). Truncated fragments were cloned into pFLAG-IL-1RAcP (kind gift of Michael Martin, Hannover, Germany), a *

Summary Thirty‐two growing rats were fed restrictively 10 semisynthetic diets which were adjusted to Se contents of 40, 70, 100, 150, 200, 300, 450, 600, 1000 and 3000 ng/g by adding Na selenite. After 3 weeks of collecting the faecal and renal excretions the animals were killed. True absorption and endogenous faecal excretions were determined by the isotope‐dilution technique after an injection of 75Se at day 7 of the experiment. True absorption and endogenous faecal excretion of Se averaged 96% and 7% of intake irrespective of the Se supply. Renal excretions accounted for 12% of intake between dietary Se levels of 40 and 100 ng/g, increased abruptly to 32% at 150 ng/g, rose degressively to a maximum of 68% at 1000 ng/g and fell to 63% at highest Se intake. The Se retention was proportional to Se intake up to dietary Se levels of 100 ng/g, remained constant up to 200 ng/g and then increased at rising extent as dietary Se rose. The tissue Se concentrations increased with rising dietary Se contents, especially between 40 and 150 ng/g and between 1000 and 3000 ng/g. The most pronounced changes were observed in the liver which acted as Se storage. In brain, testes and hair the Se concentrations remained constant except at highest Se supply. Rising Se intake intensified the elimination of injected 75Se mainly via urine and reduced the final whole body 75Se activity from 88% of injected dose at 40 ng/g to 7% at 3000 ng/g. Below 150 ng/g the contribution of liver 75Se to whole body 75Se was reduced in favour of testes and other tissues. At high Se supply, the 75Se contribution of skeletal muscles increased. This may indicate the existence of a slow exchanging or immobile Se compartment within this tissue. The recovery of injected 75Se was complete irrespective of the level of Se supply. Se exhalations were therefore not of quantitative importance. The GSH‐Px activity in blood plasma increased degressively with rising Se supply. Due to its continuous change the GSH‐Px activity could not be used to identify the transition from a deficient to a sufficient dietary Se supply. In conclusion, the homeostatic control of Se metabolism is based on the urinary Se excretion. The onset of this regulation at dietary Se levels between 100 and 150 ng/g indicates the transition of a deficient to a sufficient dietary Se supply. The compensatory capacity of Se homeostasis seems to be overloaded at dietary Se contents above 600 ng/g. Zusammenfassung Homöostatische Anpassung des Se‐Stoffwechsels sowie des Gewebeselens an eine über einen weiten Bereich hinweg variierende Se‐ Versorgung 75Se‐markierter Ratten 32 wachsende Ratten erhielten restriktiv 10 semisynthetische Diäten, deren Se‐Gehalte mit NaSelenit auf 40, 70, 100, 150, 200, 300, 450, 600, 1000 bzw. 3000 ng/g eingestellt waren. Die Kot‐ und Harnausscheidungen wurden quantitativ gesammelt und die Tiere nach 3 Wochen getötet. Die wahre Absorption und endogene fäkale Exkretion wurde über die Isotopen‐Verdünnungsmethode nach Injektion von 75Se am 7. Versuchstag ermittelt. Die wahre Abso...

Summary In a 6‐week metabolic study each of three groups of 20 growing rats were fed restrictively a semi‐synthetic diet which was supplemented with sodium selenite, seleno cysteine (SeCys) or seleno methionine (SeMet) to a total Se content of 150 ng/g. The true absorption and endogenous faecal excretions were determined by the isotope‐dilution technique after an injection of 75Se at day 7 of the experiment. The dietary selenite resulted in an apparent and true absorption of 82 and 92%, renal excretions of 36% and retention of 47% of Se intake. The SeCys increased apparent and true Se absorption to 89 and 98%, reduced renal excretions (33%) and increased retention (56%). The SeMet was equivalent to SeCys with respect to true Se absorption (99%) but caused a further increase in apparent Se absorption (92%) due to reduced endogenous faecal Se excretions. Urinary Se excretion dropped to 25% and the Se retention reached 67% of Se intake. In comparison to selenite, SeCys did not affect the Se concentrations of organs, blood, heart and femur but increased significantly that of the m. quadriceps (+18%) and numerically that of skin and hair (+6% and +11%). The SeMet increased the Se concentrations especially in the m. quadriceps (+78%), hair (+42%) and skin (+33%) but also in femur and almost all organs including brain and testes. Quantitatively, the higher Se retention of animals supplied with seleno amino acids was localized mainly within the skeletal muscles. GSH‐Px activity in blood plasma did not differ between the selenite and the SeCys group but was reduced with dietary SeMet by 5%. The cumulative 75Se excretion and residual 75Se activity in the whole body was 60 and 41% (selenite), 56 and 44% (SeCys), and 52 and 59% (SeMet). The results indicate that SeCys and SeMet are absorbed as intact amino acids which may be included unspecifically into protein synthesis. Consequently, the absorbed Se is withdrawn from the Se metabolism and the intermediate Se supply is reduced. On the other hand, Se is accumulated into tissues without the control of Se homeostasis. This effect is especially pronounced in the case of SeMet. In total, the bioavailability of the Se supplements may be ordered as follows: Selenite > SeCys > SeMet. Zusammenfassung Zum Einfluß von Selenit, Selenocystein und Selenomethionin auf den Selenstoffwechsel 75Se markierter Ratten In einem 6 wöchigen Stoffwechselversuch erhielten je 20 von insgesamt 60 wachsenden Ratten restriktiv eine semisynthetische Diät, die mit Natriumselenit, Selenocystein (SeCys) oder Selenomethionin (SeMet) auf einen Gesamtgehalt an Se von 150 ng/g supplementiert waren. Die Messung der wahren Absorption und endogenen fäkalen Exkretion an Selen erfolgte über die Isotopen‐Verdünnungsmethode nach Injektion von 75Se am 7. Versuchstag. Bei Supplementierung mit Selenit betrug die scheinbare und wahre Se‐Absorption 82 bzw. 92%, die renale Exkretion 36% und die Retention 47% der Se‐Aufnahme. SeCys erhöhte die scheinbare und wahre Absorption (89 bzw. 98%), verminderte die renale Exkretion (3...