Myb-binding Protein 1a is a Nucleocytoplasmic Shuttling Protein that Utilizes CRM1-dependent and Independent Nuclear Export Pathways

Myb-binding protein 1a (Mybbp1a) is a novel nuclear protein localized predominantly, but not exclusively, in nucleoli. Although initially isolated as a c-Myb interacting protein, Mybbp1a is expressed ubiquitously, associates with a number of different transcription factors, and may play a role in both RNA polymerase I- and II-mediated transcriptional regulation. However, its precise function remains unclear. In this study we show that Mybbp1a is a nucleocytoplasmic shuttling protein and investigate the mechanisms responsible for both nuclear import and export. The carboxyl terminus of Mybbp1a, which contains seven short basic amino acid repeat sequences, is responsible for both nuclear and nucleolar localization, and this activity can be transferred to a heterologous protein. Deletion mapping demonstrated that these repeat sequences appear to act incrementally, with successive deletions resulting in a corresponding increase in the proportion of protein localized in the cytoplasm. Glutathione S-transferase pulldown experiments showed that the nuclear receptor importin-alpha/beta mediates Mybbp1a nuclear import. Interspecies heterokaryons were used to demonstrate that Mybbp1a was capable of shuttling between the nucleus and the cytoplasm. Deletion analysis and in vivo export studies using a heterologous assay system identified several nuclear export sequences which facilitate Mybbp1a nuclear export of Mybbp1a by CRM1-dependent and -independent pathways. (C) 2003 Elsevier Science (USA). All rights reserved.

Low symbiont diversity in southern Great Barrier Reef corals, relative to those of the Caribbean

The specific identity of endosymbiotic dinoflagellates (Symbiodinium spp.) from most zooxanthellate corals is unknown. In a survey of symbiotic cnidarians from the southern Great Barrier Reef (GBR), 23 symbiont types were identified from 86 host species representing 40 genera. A majority (>85%) of these symbionts belong to a single phylogenetic clade or subgenus (C) composed of closely related (as assessed by sequence data from the internal transcribed spacer region and the ribosomal large subunit gene), yet ecologically and physiologically distinct, types. A few prevalent symbiont types, or generalists, dominate the coral community of the southern GBR, whereas many rare and/or specific symbionts, or specialists, are found uniquely within certain host taxa. The comparison of symbiont diversity between southern GBR and Caribbean reefs shows an inverse relationship between coral diversity and symbiont diversity, perhaps as a consequence of more-rapid diversification of Caribbean symbionts. Among clade C types, generalists C1 and C3 are common to both Caribbean and southern GBR symbiont assemblages, whereas the rest are regionally endemic. Possibly because of environmental changes in the Caribbean after geographic isolation through the Quaternary period, a high proportion of Caribbean fauna associate with symbiont taxa from two other distantly related Symbiodinium clades (A and B) that rarely occur in Pacific hosts. The resilience of Porites spp. and the resistance of Montipora digitata to thermal stress and bleaching are partially explained by their association with a thermally tolerant symbiont type, whereas the indiscriminant widespread bleaching and death among certain Pacific corals, during El Nino Southern Oscillation events, are influenced by associations with symbionts possessing higher sensitivity to thermal stress.

Nutrient-induced perturbations to delta C-13 and delta N-15 in symbiotic dinoilagellates and their coral hosts

Inorganic nutrients play a critical role in determining benthic community structure in tropical seas. This study examined the impact of adding inorganic nutrients (ammonium and phosphate) on the isotopic composition of 2 reef-building corals, Pocillopora damicornis and Heliofungia actiniformis, on the southern Great Barrier Reef. The addition of elevated nutrients to patch reefs that pond at low tide did not perturb the C:N ratio of either species or their symbiotic dinoflagellates. The C:N ratios were significantly higher in material extracted from the skeleton (14.8 +/- 1.50 and 10.8 +/- 1.42) than either host (7.6 +/- 0.87 and 6.0 +/- 0.71) or symbiotic dinoflagellates (5.7 +/- 0.48 and 6.9 +/- 0.66) (P. damicornis and H. actiniformis respectively; 95 confidence intervals). The ratio of acquired N to background N suggests that the added dissolved inorganic nitrogen (DIN) accounted for 50 to 100% of total nitrogen within the tissues of P. damicornis and H. actiniformis at the end of the experiment. The addition of the isotopically depleted nutrients (delta(15) N = 0parts per thousand) to patch reefs significantly decreased delta(15)N from control values of between 3 and 4 to values to below 1 in the case of all compartments, while delta(13)C values were relatively unresponsive to nutrient treatments. These findings suggest that coral delta(15)N has the potential to provide a historical record of the delta(15)N of dissolved nitrogen surrounding reef-building corals and their symbiotic dinoflagellates.

Closely related Symbiodinium spp. differ in relative dominance in coral reef host communities across environmental, latitudinal and biogeographic gradients

The diversity and community structures of symbiotic dinoflagellates are described from reef invertebrates in southern and central provinces of the Great Barrier Reef (GBR), Australia, and Zamami Island, Okinawa, Japan. The symbiont assemblages from region to region were dominated by Clade C Symbiodinium spp. and consisted of numerous host-specific and/or rare types (specialists), and several types common to many hosts (generalists). Prevalence in the host community among certain host-generalist symbionts differed between inshore and offshore environments, across latitudinal (central versus southern GBR) gradients, and over wide geographic ranges (GBR versus Okinawa). One particular symbiont (C3h) from the GBR had a dramatic shift in dominance. Its prevalence ranged from being extremely rare, or absent on high-latitude reefs to dominating the scleractinian diversity on a mid-latitude inshore reef. These changes occurred among coral fauna whose larvae must acquire symbionts from environmental sources (horizontal symbiont acquisition). Such differences did not occur among 'vertical transmitters' such as Porites spp., Montipora spp. and pocilloporids (corals that directly transmit symbionts to their offspring) or among those hosts displaying 'horizontal acquisition', but that associate with specific symbionts. Most host-specialized types were found to be characteristic of a particular geographic region (i.e. Okinawa versus Central GBR versus Southern GBR). The mode of symbiont acquisition may play an important role in how symbiont composition may shift in west Pacific host communities in response to climate change. There is no indication that recent episodes of mass bleaching have provoked changes in host-symbiont combinations from the central GBR.

Non-diagonal solutions of the reflection equation for the trigonometric A((1)) (n-1) vertex model

We obtain a class of non-diagonal solutions of the reflection equation for the trigonometric A(n-1)((1)) vertex model. The solutions can be expressed in terms of intertwinner matrix and its inverse, which intertwine two trigonometric R-matrices. In addition to a discrete (positive integer) parameter l, 1 less than or equal to l less than or equal to n, the solution contains n + 2 continuous boundary parameters.

Construction and validation of a Bovine Innate Immune Microarray

Background: Microarray transcript profiling has the potential to illuminate the molecular processes that are involved in the responses of cattle to disease challenges. This knowledge may allow the development of strategies that exploit these genes to enhance resistance to disease in an individual or animal population. Results: The Bovine Innate Immune Microarray developed in this study consists of 1480 characterised genes identified by literature searches, 31 positive and negative control elements and 5376 cDNAs derived from subtracted and normalised libraries. The cDNA libraries were produced from 'challenged' bovine epithelial and leukocyte cells. The microarray was found to have a limit of detection of 1 pg/mu g of total RNA and a mean slide-to-slide correlation co-efficient of 0.88. The profiles of differentially expressed genes from Concanavalin A ( ConA) stimulated bovine peripheral blood lymphocytes were determined. Three distinct profiles highlighted 19 genes that were rapidly up-regulated within 30 minutes and returned to basal levels by 24 h; 76 genes that were upregulated between 2 - 8 hours and sustained high levels of expression until 24 h and 10 genes that were down-regulated. Quantitative real-time RT-PCR on selected genes was used to confirm the results from the microarray analysis. The results indicate that there is a dynamic process involving gene activation and regulatory mechanisms re-establishing homeostasis in the ConA activated lymphocytes. The Bovine Innate Immune Microarray was also used to determine the cross-species hybridisation capabilities of an ovine PBL sample. Conclusion: The Bovine Innate Immune Microarray has been developed which contains a set of well-characterised genes and anonymous cDNAs from a number of different bovine cell types. The microarray can be used to determine the gene expression profiles underlying innate immune responses in cattle and sheep.

Molecular orbital calculations of two-electron states for P-donor solid-state spin qubits

We theoretically study the Hilbert space structure of two neighboring P-donor electrons in silicon-based quantum computer architectures. To use electron spins as qubits, a crucial condition is the isolation of the electron spins from their environment, including the electronic orbital degrees of freedom. We provide detailed electronic structure calculations of both the single donor electron wave function and the two-electron pair wave function. We adopted a molecular orbital method for the two-electron problem, forming a basis with the calculated single donor electron orbitals. Our two-electron basis contains many singlet and triplet orbital excited states, in addition to the two simple ground state singlet and triplet orbitals usually used in the Heitler-London approximation to describe the two-electron donor pair wave function. We determined the excitation spectrum of the two-donor system, and study its dependence on strain, lattice position, and interdonor separation. This allows us to determine how isolated the ground state singlet and triplet orbitals are from the rest of the excited state Hilbert space. In addition to calculating the energy spectrum, we are also able to evaluate the exchange coupling between the two donor electrons, and the double occupancy probability that both electrons will reside on the same P donor. These two quantities are very important for logical operations in solid-state quantum computing devices, as a large exchange coupling achieves faster gating times, while the magnitude of the double occupancy probability can affect the error rate.

Less inhibited with age? Larval age modifies responses to natural settlement inhibitors

As larvae of marine invertebrates age, their response to settlement cues can change. This change can have significant consequences to both the ecology of these organisms, and to their response to antifouling coatings. This study examines how larval age affects the settlement response of larvae to two naturally derived settlement inhibitors, non-polar extracts from the algae Delisea pulchra and Dilophus marginatus, the former of which contains compounds that are in commercial development as antifoulants. Two species of marine invertebrates with non-feeding larvae were investigated: the bryozoans Watersipora subtorquata and Bugula neritina. Larval age strongly affected larval settlement, with older larvae settling at much higher rates than younger larvae. Despite having strong, inhibitory effects on young larvae, the non-polar extracts did not inhibit the settlement of older larvae to the same degree for both species studied. The results show that the effects of ecologically realistic settlement inhibitors are highly dependent on larval age. Given that the age of settling larvae is likely to be variable in the field, such age specific variation in settlement response of larvae may have important consequences for host-epibiont interactions in natural communities.

Algebraic Bethe ansatz for the anisotropic supersymmetric U model

We present an algebraic Bethe ansatz for the anisotropic supersymmetric U model for correlated electrons on the unrestricted 4(L)-dimensional electronic Hilbert space x(n=l)(L)C(4)(where L is the lattice length). The supersymmetry algebra of the local Hamiltonian is the quantum superalgebra U-q[gl(2\1)] and the model contains two symmetry-preserving free real parameters; the quantization parameter q and the Hubbard interaction parameter U. The parameter U arises from the one-parameter family of inequivalent typical four-dimensional irreps of U-q[gl(2\1)]. Eigenstates of the model are determined by the algebraic Bethe ansatz on a one-dimensional periodic lattice.

Biological activity and metabolic clearance of recombinant human follicle stimulating hormone produced in Sp2/0 myeloma cells

Human follicle stimulating hormone is a pituitary glycoprotein that is essential for the maintenance of ovarian follicle development and testicular spermatogenesis. Like other members of the glycoprotein hormone family, it contains a common a subunit and a hormone specific beta subunit. Each subunit contains two glycosylation sites. The specific structures of the oligosaccharides of human follicle stimulating hormone have been shown to influence both the in vitro and in vivo bioactivity. Since the carbohydrate structure of a protein reflects the glycosylation apparatus of the host cells in which the protein is expressed, we examined the isoform profiles, in vitro bioactivity and metabolic clearance of a preparation of purified recombinant human follicle stimulating hormone derived from a stable, transfected Sp2/0 myeloma cell line, and pituitary human follicle stimulating hormone. Isoelectric focussing and chromatofocussing studies of human follicle stimulating hormone preparations both showed a more basic isoform profile for the recombinant human follicle stimulating hormone compared to that of pituitary human follicle stimulating hormone. The recombinant human follicle stimulating hormone had a significantly higher radioreceptor activity compared to that of pituitary human follicle stimulating hormone, consistent with a greater in vitro potency. Pharmacokinetic studies in rats indicated a similar terminal half life (124 min) to that of the pituitary human follicle stimulating hormone (119 min). Preliminary carbohydrate analysis showed recombinant human follicle stimulating hormone to contain high mannose and/or hybrid type, in addition to complex type carbohydrate chains, terminating with both alpha 2,3 and alpha 2,6 linked sialic acids. These results demonstrate that recombinant human follicle stimulating hormone made in the Sp2/0 myeloma cells is sialylated, has a more basic isoform profile, and has a greater in vitro biological potency compared to those of the pituitary human follicle stimulating hormone.

The Parkes half-jansky flat-spectrum sample

We present a new sample of Parkes half-jansky flat-spectrum radio sources, having made a particular effort to find any previously unidentified sources. The sample contains 323 sources selected according to a flux limit of 0.5 Jy at 2.7 GHz, a spectral index measured between 2.7 and 5.0 GHz of alpha(2.7/5.0) > -0.5, where S(nu) proportional to nu(alpha), Galactic latitude \b\ > 20 degrees and -45 degrees < declination (B1950) < +10 degrees. The sample was selected from a region 3.90 steradians in area. We have obtained accurate radio positions for all the unresolved sources in this sample, and combined these with accurate optical positions from digitized photographic sky survey data to check all the optical identifications. We report new identifications based on R- and Kn-band imaging and new spectroscopic measurements of many of the sources. We present a catalogue of the 323 sources, of which 321 now have identified optical counterparts and 277 have measured spectral redshifts.

MHCPEP, a database of MHC-binding peptides: Update 1996

MHCPEP is a curated database comprising over 9000 peptide sequences known to bind MHC molecules. Entries are compiled from published reports as well as from direct submissions of experimental data. Each entry contains the peptide sequence, its MHC specificity and, when available, experimental method, observed activity, binding affinity, source protein, anchor positions and publication references. The present format of the database allows text string matching searches but can easily be converted for use in conjunction with sequence analysis packages. The database can be accessed via Internet using WWW, FTP or Gopher.

Pirellulosomes: A new type of membrane-bounded cell compartment in planctomycete bacteria of the genus Pirellula

A distinct type of cellular organization was found in two species of the planctomycete genus Pirellula, Pirellula marina and Pirellula staleyi. Both species possess two distinct regions within the cell which are separated by a single membrane. The major region of the cell, the pirellulosome, contains the fibrillar condensed nucleoid. The other area, the polar cap region, forms a continuous layer surrounding the entire pirellulosome and displays a cap of asymmetrically distributed material at one cell pole. Immuno- and cytochemical-labelling of P. marina demonstrated that DNA is located exclusively within the pirellulosome; cell RNA is concentrated in the pirellulosome, with some RNA also located in the polar cap region.

Encephalitogenicity of murine, but not bovine, DM20 in SJL mice is due to a single amino acid difference in the immunodominant encephalitogenic epitope

Myelin proteolipid protein (PLP) contains 2 immunodominant encephalitogenic epitopes in SJL mice, namely PLP residues 139-151 and 178-191. DM20, a minor isoform of PLP, lacks residues 116-150 and consequently contains only the single major encephalitogenic epitope 178-191. However, it has been found previously that bovine DM20 is not encephalitogenic in SJL mice. Since residue 188 within peptide 178-191 is phenylalanine (F) in murine DM20 and alanine (A) in bovine DM20, we tested the effect of this difference on the immune responses and induction of EAE. SJL mice were immunized with either highly purified murine or bovine DM20. Residues 178-191 were found to be immunodominant for each, but only murine and not bovine DM20 was encephalitogenic. A synthetic peptide corresponding to the murine 178-191 sequence (F188) was also encephalitogenic, whereas the peptide corresponding to the bovine sequence (A188) was not. Both F188 and A188 bind with high affinity to I-A(s) and both are recognized by the SJL T cell repertoire. A188-specific T cell lines reacted to both A188 and F188, but F188-specific T cell lines were not stimulated by A188. F188-specific T cell lines produced mRNA for the Th1 cytokines IL2 and IFN gamma and, in passive transfer experiments, were encephalitogenic upon stimulation with F188, but not A188. In contrast, A188-specific T cell lines produced mRNA for IL4, IL5 and IL10, in addition to IL2 and IFN gamma, and were not encephalitogenic after stimulation with either F188 or A188. Cotransfer of A188-specific T cell lines with F188-specific T cell lines resulted in protection from EAE. Thus, A188 induces a functionally different phenotype of T cells from that induced by F188. Taken together these data suggest that the failure of bovine DM20 to induce EAE may be attributable to induction of protective rather than pathogenic T cells by the immunodominant epitope.

The myosin-I-binding protein Acan125 binds the SH3 domain and belongs to the superfamily of leucine-rich repeat proteins

The SH3 domains of src and other nonreceptor tyrosine kinases have been shown to associate with the motif PXXP, where P and X stand for proline and an unspecified amino acid, but a motif that binds to the SH3 domain of myosin has thus far not been characterized. We previously showed that the SH3 domain of Acanthamoeba myosin-IC interacts with the protein Acan125. We now report that the Acan125 protein sequence contains two tandem consensus PXXP motifs near the C terminus. To test for binding, we expressed a polypeptide, AD3p, which includes 344 residues of native C-terminal sequence and a mutant polypeptide, AD3 Delta 977-994p, which lacks the sequence RPKPVPPPRGAKPAPPPR containing both PXXP motifs. The SH3 domain of Acanthamoeba myosin-IC bound AD3p and not AD3 Delta 977-994p, showing that the PXXP motifs are required for SH3 binding. The sequence of Acan125 is related overall to a protein of unknown function coded by Caenorhabditis elegans gene K07G5.1. The K07G5.1 gene product contains a proline-rich segment similar to the SH3 binding motif found in Acan125. The aligned sequences show considerable conservation of leucines and other hydrophobic residues, including the spacing of these residues, which matches a motif for leucine-rich repeats (LRRs). LRR domains have been demonstrated to be sites for ligand binding. Having an LRR domain and an SH3-binding domain, Acan125 and the C. elegans homologue define a novel family of bifunctional binding proteins.