| 1. |
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| 2. |
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| 3. |
- Berg, OG, et al.
(författare)
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Fluctuations in repressor control: Thermodynamic constraints on stochastic focusing
- 2000
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Ingår i: BIOPHYSICAL JOURNAL. - : BIOPHYSICAL SOCIETY. - 0006-3495. ; 79:6, s. 2944-2953
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Tidskriftsartikel (refereegranskat)abstract
- The influence of fluctuations in molecule numbers on genetic control circuits has received considerable attention. The consensus has been that such fluctuations will make regulation less precise. In contrast, it has more recently been shown that signal fl
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| 4. |
- Buffoni Hall, Roberta, et al.
(författare)
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Water- and temperature-dependence of DNA damage and repair in the fruticose lichen Cladonia arbuscula ssp mitis exposed to UV-B radiation
- 2003
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317. ; 118:3, s. 371-379
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Tidskriftsartikel (refereegranskat)abstract
- The induction of cyclobutane pyrimidine dimers (CPDs) by ultraviolet-B radiation (UV-B, 280-315 nm) and repair mechanisms were studied in the lichen Cladonia arbuscula ssp. mitis exposed to different temperatures and water status conditions. In addition, the development and repair of CPDs were studied in relation to the different developmental stages of the lichen thallus podetial branches. Air-dried lichen thalli exposed to UV-B radiation combined with relatively high visible light (HL, 800 mumol m(-2) s(-1); 400-700 nm) for 7 days showed a progressive increase of CPDs with no substantial repair, although HL was present during and after irradiation with UV-B. Fully hydrated lichen thalli, that had not been previously exposed to UV-B radiation for 7 days, were given short-term UV-B radiation treatment at 25degreesC, and accumulated DNA lesions in the form of CPDs, with repair occurring when they were exposed to photoreactivating conditions (2 h of 300 mumol m(-2)s(-1), 400-700 nm). A different pattern was observed when fully hydrated thalli were exposed to short-term UV-B radiation at 2degreesC, in comparison with exposure at 25degreesC. High levels of CPDs were induced at 2degreesC under UV-B irradiation, without significant repair under subsequent photoreactivating light. Likewise, when PAR (300 mumol m(-2)s(-1) ) and UV-B radiation were given simultaneously, the CPD levels were not lowered. Throughout all experiments the youngest, less differentiated parts of the lichen thallus - namely 'tips', according to our arbitrary subdivision - were the parts showing the highest levels of CPD accumulation and the lowest levels of repair in comparison with the older thallus tissue ('stems'). Thus the experiments showed that Cladonia arbuscula ssp. mitis is sensitive to UV-B irradiation in the air-dried state and is not able to completely repair the damage caused by the radiation. Furthermore, temperature plays a role in the DNA damage repairing capacity of this lichen, since even when fully hydrated, C. arbuscula ssp. mitis did not repair DNA damage at the low temperatures.
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| 5. |
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| 7. |
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| 8. |
- Klatt, A R, et al.
(författare)
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Molecular structure and tissue distribution of matrilin-3, a filament-forming extracellular matrix protein expressed during skeletal development
- 2000
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 275:6, s. 3999-4006
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Tidskriftsartikel (refereegranskat)abstract
- Matrilin-3 is a recently identified member of the superfamily of proteins containing von Willebrand factor A-like domains and is able to form hetero-oligomers with matrilin-1 (cartilage matrix protein) via a C-terminal coiled-coil domain. Full-length matrilin-3 and a fragment lacking the assembly domain were expressed in 293-EBNA cells, purified, and subjected to biochemical characterization. Recombinantly expressed full-length matrilin-3 occurs as monomers, dimers, trimers, and tetramers, as detected by electron microscopy and SDS-polyacrylamide gel electrophoresis, whereas matrilin-3, purified from fetal calf cartilage, forms homotetramers as well as hetero-oligomers of variable stoichiometry with matrilin-1. In the matrix formed by cultured chondrosarcoma cells, matrilin-3 is found in a filamentous, collagen-dependent network connecting cells and in a collagen-independent pericellular network. Affinity-purified antibodies detect matrilin-3 expression in a variety of mouse cartilaginous tissues, such as sternum, articular, and epiphyseal cartilage, and in the cartilage anlage of developing bones. It is found both inside the lacunae and in the interterritorial matrix of the resting, proliferating, hypertrophic, and calcified cartilage zones, whereas the expression is lower in the superficial articular cartilage. In trachea and in costal cartilage of adult mice, an expression was seen in the perichondrium. Furthermore, matrilin-3 is found in bone, and its expression is, therefore, not restricted to chondroblasts and chondrocytes.
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| 9. |
- Lazar, A., et al.
(författare)
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An effective hopping model for weakly interacting p systems : Electronic structure of stacked polyaromatic hydrocarbons
- 2001
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Ingår i: International Journal of Quantum Chemistry. - : Wiley. - 0020-7608 .- 1097-461X. ; 84:2, s. 216-225
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Parameters for effective hopping integrals are extracted from ab initio Hartree-Fock calculations on model systems. These effective hoppings can be used to describe the attractive part of the interaction of loosely bonded p-electron systems of various orientations, such as interchain hoppings in conjugated polymers or those between two-dimensional graphitic sheets.
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| 10. |
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| 11. |
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| 12. |
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| 15. |
- Paulsson, JP, et al.
(författare)
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Molecular clocks reduce plasmid loss rates: The R1 case
- 2000
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Ingår i: JOURNAL OF MOLECULAR BIOLOGY. - : ACADEMIC PRESS LTD. - 0022-2836. ; 297:1, s. 179-192
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Tidskriftsartikel (refereegranskat)abstract
- Plasmids control their replication so that the replication frequency per plasmid copy responds to the number of plasmid copies per cell. High sensitivity amplification in replication response to copy number deviations generally reduces variation in copy n
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| 16. |
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| 17. |
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| 18. |
- Paulsson, J, et al.
(författare)
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Stochastic focusing: Fluctuation-enhanced sensitivity of intracellular regulation
- 2000
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Ingår i: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - : NATL ACAD SCIENCES. - 0027-8424. ; 97:13, s. 7148-7153
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Tidskriftsartikel (refereegranskat)abstract
- Many regulatory molecules are present in low copy numbers per cell so that significant random fluctuations emerge spontaneously. Because cell viability depends on precise regulation of key events, such signal noise has been thought to impose a threat that
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| 19. |
- Paulsson, Kajsa M, et al.
(författare)
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Assembly of tapasin-associated MHC class I in the absence of the transporter associated with antigen processing (TAP)
- 2001
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Ingår i: International Immunology. - : Oxford University Press (OUP). - 0953-8178 .- 1460-2377. ; 13:1, s. 9-23
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Tidskriftsartikel (refereegranskat)abstract
- The assembly of MHC class I molecules is regulated by a multi-protein complex in the endoplasmic reticules (ER) termed the loading complex. Tapasin is suggested to be one of the molecules forming this complex on the basis of its interaction with both the transporter associated with antigen processing (TAP) and MHC class I molecules. To address whether TAP is indispensable for the processing of the assembly of tapasin-associated MHC class I molecules, we studied the association of MHC class I molecules with tapasin, the assembly of tapasin-associated MHC class I with peptides and the peptide-mediated dissociation of MHC class I from tapasin in TAP-mutant T2 cells. In the absence of TAP, MHC class I heavy chain and beta(2)-microglobulin dimers were found to be properly associated with tapasin. The stable MHC class I dimer was required for its association with tapasin in the ER. In the absence of TAP, tapasin retained MHC class I molecules much longer in the ER than in the presence of TAP. This low off-rate of MHC class I from tapasin was due to the absence of high-affinity peptides in the ER of TAP-mutant cells but not to the absence of TAP per se. The introduction of peptides into permeabilized microsomes of TAP-mutant cells led to effective loading of the peptides onto tapasin-associated MHC class I and to the subsequent dissociation of MHC class I from tapasin. These results demonstrate that regulation of the assembly of tapasin-associated MHC class I is independent of the interaction of tapasin with TAP, but is dependent upon the peptides transported by TAP.
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| 20. |
- Paulsson, Kajsa M, et al.
(författare)
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Association of tapasin and COPI provides a mechanism for the retrograde transport of major histocompatibility complex (MHC) class I molecules from the Golgi complex to the endoplasmic reticulum
- 2002
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 277:21, s. 18266-18271
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Tidskriftsartikel (refereegranskat)abstract
- Tapasin is a subunit of the transporter associated with antigen processing (TAP). It associates with the major histocompatibility complex (MHC) class I. We show that tapasin interacts with beta- and gamma-subunits of COPI coatomer. COPI retrieves membrane proteins from the Golgi network back to the endoplasmic reticulum (ER). The COPI subunit-associated tapasin also interacts with MHC class I molecules suggesting that tapasin acts as the cargo receptor for packing MHC class I molecules as cargo proteins into COPI-coated vesicles. In tapasin mutant cells, neither TAP nor MHC class I are detected in association with the COPI coatomer. Interestingly, tapasin-associated MHC class I molecules are antigenic peptide-receptive and detected in both the ER and the Golgi. Our data suggest that tapasin is required for the COPI vesicle-mediated retrograde transport of immature MHC class I molecules from the Golgi network to the ER.
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| 21. |
- Paulsson, Kajsa M, et al.
(författare)
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Chaperones and folding of MHC class I molecules in the endoplasmic reticulum.
- 2003
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Ingår i: Biochimica et Biophysica Acta. - 0006-3002. ; 1641:1, s. 1-12
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Forskningsöversikt (refereegranskat)abstract
- In this review we discuss the influence of chaperones on the general phenomena of folding as well as on the specific folding of an individual protein, MHC class I. MHC class I maturation is a highly sophisticated process in which the folding machinery of the endoplasmic reticulum (ER) is heavily involved. Understanding the MHC class I maturation per se is important since peptides loaded onto MHC class I molecules are the base for antigen presentation generating immune responses against virus, intracellular bacteria as well as tumours. This review discusses the early stages of MHC class I maturation regarding BiP and calnexin association, and differences in MHC class I heavy chain (HC) interaction with calnexin and calreticulin are highlighted. Late stage MHC class I maturation with focus on the dedicated chaperone tapasin is also discussed. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 22. |
- Paulsson, K M, et al.
(författare)
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Distinct differences in association of MHC class I with endoplasmic reticulum proteins in wild-type, and beta 2-microglobulin- and TAP-deficient cell lines
- 2001
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Ingår i: International Immunology. - : Oxford University Press (OUP). - 0953-8178 .- 1460-2377. ; 13:8, s. 73-1063
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Tidskriftsartikel (refereegranskat)abstract
- In this study we have compared the interaction of human MHC class I molecules with IgG heavy chain (HC) binding protein (BiP), calnexin, calreticulin, tapasin and TAP in beta(2)-microglobulin (beta(2)m)- or TAP-deficient cells, as well as in wild-type B-LCL cells. Distinct differences between the association of HC and these endoplasmic reticulum (ER) proteins were found in the three cell lines. In the absence of beta(2)m (Daudi cells), HC associated with both BiP and calnexin. A prominent portion of HC was complexed simultaneously to both chaperones, as indicated by co-precipitation with either anti-calnexin or anti-class I antisera. In the presence of beta(2)m, but absence of TAP (T2 cells), HC could be co-precipitated with calnexin, whereas no detectable interaction with BiP could be demonstrated. This suggests that calnexin interacts with HC at a later stage than BiP. In B-LCL cells, HC-beta(2)m associated with calreticulin and tapasin, whereas no interaction with calnexin and BiP was observed. In the absence of beta(2)m, HC were rapidly degraded in the ER, while the ER retained HC were stabilized in the presence of beta(2)m, even in the absence of TAP. The dissociation of class I molecules from TAP in B-LCL cells correlated with the kinetics of appearance of class I molecules on the cell surface, suggesting that TAP retains peptide-free class I molecules in the ER. Taken together, our results suggest the model that BiP and calnexin sequentially control the folding of MHC class I, before MHC class I molecules associate with the loading complex.
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| 23. |
- Paulsson, Kajsa M
(författare)
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The quality control of MHC class I antigen presentation
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Major histocompatibility complex (MHC) class I molecules present antigenic peptides to CD8+ T cells. The peptides are generated by proteasomes in the cytosol, then translocated across the membrane of the endoplasmic reticulum (ER) by the transporter associated with antigen processing (TAP). Only properly assembled class I molecules loaded with high affinity peptides reach the cell surface. The maturation process is performed in a sequential mode where the chaperones BiP and calnexin sequentially control the folding of the MHC class I. Dimerised MHC class I then associate with the loading complex (paper I). An essential component of the loading complex is the trimeric complex consisting of TAP1, TAP2, and tapasin as shown in paper II. Due to its ability to interact with TAP and MHC class I, tapasin is a central component in the assembly of MHC class I. Efficient peptide binding by TAP prior to translocation across the ER membrane requires the presence of tapasin (paper III). Once in the ER, the assembly of tapasin-associated MHC class I with peptide depends on the presence of TAP transported peptides (paper IV). The transport of stably loaded class I molecules to the cell surface goes through the secretory route. Tapasin interacts specifically with COPI vesicles, possibly allowing recycling of unstable class I molecules from the Golgi back to the ER (paper V).
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| 24. |
- Paulsson, M., et al.
(författare)
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Conductance calculations through stacks of polyaromatic hydrocarbons
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 121:1-3, s. 1273-1274
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Tidskriftsartikel (refereegranskat)abstract
- Polyaromatic hydrocarbons (PAH) can be synthesized many different sizes. They form self-assembled stacks of molecules which could be utilized in nanoelectronics applications. In this work we study stacks of PAH contacted to multichannel metallic leads. The conductance is calculated using the Landauer formula for the neutral and alkali doped stacks of PAH. We show that in the non-resonance tunneling limit the conductance is linearly related to the size of the individual PAH. A simple expression is shown to approximately describe the dependence of the conductance on the number of molecules in a stack as well as the inter-molecular interaction.
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| 25. |
- Paulsson, M., et al.
(författare)
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Theoretical study of electron transport along self-assembled graphitic nanowires
- 2000
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 12:45, s. 9433-9440
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Tidskriftsartikel (refereegranskat)abstract
- Electron transport through stacks of polyaromatic hydrocarbons is studied theoretically using the Landauer formalism. The polyaromatic hydrocarbons can be synthesized in many different sizes and can form molecular stacks with a varying number of molecules and with a rather strong p-overlap along the stack. This allows for a large flexibility in the nanostructure of these materials and makes it possible to study the variation in the conductance with a number of different factors: a near-linear increase in the conductance as a function of the number of atoms in the individual molecule is observed. Furthermore, the conductance drops exponentially with the number of molecules in the stacks, from which it follows that an increase in the intermolecular hopping results in an increase in the conductance which is proportional to the intermolecular hopping to the power of 2(N-1), where N is the number of molecules in the stack.
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| 26. |
- Piecha, D, et al.
(författare)
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Matrilin-2 interacts with itself and with other extracellular matrix proteins
- 2002
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Ingår i: Biochemical Journal. - 0264-6021. ; 367:3, s. 715-721
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Tidskriftsartikel (refereegranskat)abstract
- Matrilin-2 is a component of extracellular filamentous networks. To study the interactions by which it can be integrated into such assemblies, full-length and truncated forms of matrilin-2 were recombinantly expressed in HEK-293 cells and purified from conditioned medium. The recombinant proteins, when used in interaction assays, showed affinity to matrilin-2 itself, but also to other collagenous and non-collagenous extracellular matrix proteins. The interaction between matrilin-2 and collagen I was studied in greater detail and could be shown to occur at distinct sites on the collagen I molecule and to have a K-D of about 3 x 10(-8) M. Interactions with some non-collagenous protein ligands were even stronger, with matrilin-2 binding to fibrillin-2, fibronectin and laminin-1-nidogen-1 complexes, with K-D values in the range of 10(-8)-10(-11) M. Co-localization of matrilin-2 with these ligands in the dermal-epidermal basement membrane, in the microfibrils extending from the basement membrane into the dermis, and in the dermal extracellular matrix, indicates a physiological relevance of the interactions in the assembly of supramolecular extracellular matrix structures.
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| 27. |
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| 28. |
- Sengle, G, et al.
(författare)
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Identification and characterization of AMACO, a new member of the von Willebrand factor A-like domain protein superfamily with a regulated expression in the kidney
- 2003
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 278:50, s. 50240-50249
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Tidskriftsartikel (refereegranskat)abstract
- The genes coding for human and mouse AMACO, an extracellular matrix protein containing VWA-like domains related to those in MAtrilins and COllagens, were detected in databases, the cDNAs were cloned, and the primary structures were deduced from the nucleotide sequences. The genes consist of 14 exons and have a similar exon/intron organization. The protein consists of a signal peptide sequence, an N-terminal VWA domain connected to two additional, tandem VWA domains by a cysteine-rich sequence and an epidermal growth factor (EGF)-like domain. The C terminus is made up of another EGF-like domain followed by a unique sequence present in mouse, but absent in human. The predicted molecular weight of the proteins is 79,485 in human and 83,024 in mouse. Full-length AMACO was expressed in 293-EBNA cells, purified by use of an affinity tag and subjected to biochemical characterization. Both monomers and aggregates of AMACO were recovered, as shown by electron microscopy and SDS-PAGE. AMACO was found in the media of a variety of established cell lines of both fibroblast and epithelial origin. In the matrix formed by 293-EBNA cells overexpressing the protein, AMACO was deposited in patchy structures that were often cell-associated. Affinity-purified antibodies detect expression in cartilage and expression associated with certain basement membranes. In the kidney of adult mice, a second promoter located in intron 4 is active. If the resulting transcript is translated it could not yield a secreted protein because of the lack of a signal peptide sequence. The developmental switch from an AMACO mRNA, expressed by the newborn kidney, to the truncated transcript found in the adult kidney indicates an unusual regulation of AMACO expression.
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| 29. |
- Wang, P, et al.
(författare)
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Inhibition of the transcription factors AP-1 and NF-kappaB in CD4 T cells by peroxisome proliferator-activated receptor gamma ligands
- 2001
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Ingår i: International Immunopharmacology. - 1567-5769. ; 1:4, s. 12-803
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Tidskriftsartikel (refereegranskat)abstract
- The peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor superfamily, is essential for adipocyte differentiation and glucose homeostasis. PPARgamma has been found recently to regulate macrophage activation in response to mitogens and inflammation. Our study shows PPARgamma to be preferentially expressed in the nuclei of resting T cells and to increase upon activation of T cells by either anti-CD3 and anti-CD28 or phorbol myristyl acetate (PMA). We also found the PPARgamma ligand ciglitizone to attenuate the activation of T cells by inhibiting cytokine gene expression and anti-CD3 and anti-CD28 or PMA-induced proliferative responses. Inhibition of both the proliferative response and inflammatory cytokine expression in CD4 T cells was correlated with suppression of the activated transcription factors AP1 and NF-kappaB. PPARgamma ligands also strongly inhibited SEA-induced Vbeta3 T cell activation in vivo. These results, together with previous findings of the inhibitory effect of PPARgamma ligands on activated macrophages, provide clear evidence for PPARgamma as a negative regulator of the inflammatory activation of both macrophage and T cells. PPARgamma may thus be a potential therapeutic target for the treatment of autoimmunity.
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