| 1. |
- Mårtensson, Annica, et al.
(författare)
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PEBP2 and c-myb sites crucial for lambda5 core enhancer activity in pre-B cells.
- 2001
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Ingår i: European Journal of Immunology. - 0014-2980 .- 1521-4141. ; 31:11, s. 3165-3174
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Tidskriftsartikel (refereegranskat)abstract
- The lambda5 gene is expressed exclusively in precursor (pre-) B cells where its gene product, as part of the pre-B cell receptor, is crucial for the proliferation of these cells. Several DNA regions regulate the activity and expression pattern of the lambda5 gene. Amongst these is an enhancer, B(lambda5), located 5' of the gene. Here we analyze the lambda5 enhancer core, b(lambda5), which in earlier experiments was demonstrated to retain 50% of the enhancer activity, and show that this activity is restricted to pre-B cells. We identify a DNA element within b(lambda5), PEBP2(lambda5), which is essential for enhancer activity: mutation within this site dramatically reduces core enhancer activity in pre-B cells. The PEBP2(lambda5) site binds bacterially produced polyoma enhancer binding proteins (PEBP) (Runx/AML/CBFA). Furthermore, PEBP2 proteins present in nuclear extracts from murine pre-B cells bind to the PEBP2(lambda5) element. PEBP2 proteins in mature B cells also bind to the PEBP2(lambda5 )element, implying that if PEBP2 proteins are responsible for the stage-specific expression, they have to be non-activating or inhibiting in mature B cells. We also demonstrate that a described partner of PEBP2, c-myb, binds to a sequence termed myb(lambda5) located just upstream of the PEBP2(lambda5) site in the core enhancer. The myb(lambda5) element is also crucial for enhancer activity, since mutating the myb site reduces core enhancer activity to the same extent as mutating the PEBP2 site. Earlier reports have shown that c-myb is expressed at high levels in pre-B cell lines whereas its expression is down-regulated in more mature B cell lines. Thus, c-myb may be involved in determining the stage-specific expression of the lambda5 gene.
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| 2. |
- Struthers, Hamish, et al.
(författare)
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Climate-induced changes in sea salt aerosol number emissions : 1870 to 2100
- 2013
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Ingår i: Journal of Geophysical Research-Atmospheres. - : American Geophysical Union (AGU). - 2169-897X. ; 118:2, s. 670-682
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Tidskriftsartikel (refereegranskat)abstract
- Global climate model output is combined with an emission parameterization to estimate the change in the global and regional sea salt aerosol number emission from 1870 to 2100. Global average results suggest a general increase in sea salt aerosol number emission due to increasing surface wind speed. However, the emission changes are not uniform over the aerosol size spectrum due to an increase in sea surface temperature. From 1870 to 2100 the emission of coarse mode particles (dry diameter D-P > 655 nm) increase by approximately 10 % (global average), whereas no significant change in the emission of ultrafine mode aerosols (dry diameter D-p < 76 nm) was found over the same period. Significant regional differences in the number emission trends were also found. Based on CAM-Oslo global climate model output, no straight-forward relationship was found between the change in the number emissions and changes in the sea salt aerosol burden or optical thickness. This is attributed to a change in the simulated residence time of the sea salt aerosol. For the 21st century, a decrease in the residence time leads to a weaker sea salt aerosol-climate feedback that what would be inferred based on changes in number emissions alone. Finally, quantifying any potential impact on marine stratocumulus cloud microphysical and radiative properties due to changes in sea salt aerosol number emissions is likely to be complicated by commensurate changes in anthropogenic aerosol emissions and changes in meteorology.
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| 3. |
- Bemark, Mats, et al.
(författare)
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Spi-C, a novel Ets protein that is temporally regulated during B lymphocyte development
- 1999
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Ingår i: Journal of Biological Chemistry. - : Elsevier BV. - 0021-9258. ; 274:15, s. 10259-10267
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Tidskriftsartikel (refereegranskat)abstract
- A novel Ets protein was isolated by yeast one-hybrid screening of a cDNA library made from lipopolysaccharide-stimulated mouse splenic B cells, using the SP6 κ promoter κY element as a bait. The novel Ets protein was most closely related to PU.1 and Spi-B within the DNA binding Ets domain and was therefore named Spi-C. However, Spi-C may represent a novel subgroup within the Ets protein family, as it differed significantly from Spi-B and PU.1 within helix 1 of the Ets domain. Spi-C was encoded by a single-copy gene that was mapped to chromosome 10, region C. Spi-C interacted with DNA similarly to PU.1 as judged by methylation interference, band-shift and site selection analysis, and activated transcription of a κY element reporter gene upon co-transfection of HeLa cells. Spi-C RNA was expressed in mature B lymphocytes and at lower levels in macrophages. Furthermore, pre-B cell and plasma cell lines were Spi-C-negative, suggesting that Spi-C might be a regulatory molecule during a specific phase of B lymphoid development.
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| 4. |
- Blissing, Annica
(författare)
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Thiopurine S-methyltransferase - characterization of variants and ligand binding
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thiopurine S-methyltransferase (TPMT) belongs to the Class I S-adenosylmethionine-dependent methyltransferase (SAM-MT) super family of structurally related proteins. Common to the members of this large protein family is the catalysis of methylation reactions using S-adenosylmethionine (SAM) as a methyl group donor, although SAM-MTs act on a wide range of different substrates and carry out numerous biologically important functions. While the natural function of TPMT is unknown, this enzyme is involved in the metabolism of thiopurines, a class of pharmaceutical substances administered in treatment of immune-related disorders. Specifically, methylation by TPMT inactivates thiopurines and their metabolic intermediates, which reduces the efficacy of clinical treatment and increases the risk of adverse side effects. To further complicate matters, TPMT is a polymorphic enzyme with over 40 naturally occurring variants known to date, most of which exhibit lowered methylation activity towards thiopurines. Consequently, there are individual variations in TPMTmediated thiopurine inactivation, and the administered dose has to be adjusted prior to clinical treatment to avoid harmful side effects.Although the clinical relevance of TPMT is well established, few studies have investigated the molecular causes of the reduced methylation activity of variant proteins. In this thesis, the results of biophysical characterization of two variant proteins, TPMT*6 (Y180F) and TPMT*8 (R215H), are presented. While the properties of TPMT*8 were indistinguishable from those of the wild-type protein, TPMT*6 was found to be somewhat destabilized. Interestingly, the TPMT*6 amino acid substitution did not affect the functionality or folding pattern of the variant protein. Therefore, the decreased in vivo functionality reported for TPMT*6 is probably caused by increased proteolytic degradation in response to the reduced stability of this protein variant, rather than loss of function.Also presented herein are novel methodological approaches for studies of TPMT and its variants. Firstly, the advantages of using 8-anilinonaphthalene-1-sulfonic acid (ANS) to probe TPMT tertiary structure and active site integrity are presented. ANS binds exclusively to the native state of TPMT with high affinity (KD ~ 0.2 μm) and a 1:1 ratio. The stability of TPMT was dramatically increased by binding of ANS, which was shown to co-localize with the structurally similar adenine moiety of the cofactor SAM. Secondly, an enzyme activity assay based on isothermal titration calorimetry (ITC) is presented. Using this approach, the kinetics of 6-MP and 6-TG methylation by TPMT has been characterized.
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| 5. |
- Bobjer, Johannes, et al.
(författare)
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Location of retroperitoneal lymph node metastases in upper tract urothelial carcinoma : results from a prospective lymph node mapping study
- 2023
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Ingår i: European Urology Open Science. - : Elsevier. - 2666-1691 .- 2666-1683. ; 57, s. 37-44
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Tidskriftsartikel (refereegranskat)abstract
- Background: There is limited information on the distribution of retroperitoneal lymph node metastases (LNMs) in upper tract urothelial carcinoma (UTUC).Objective: To investigate the location of LNMs in UTUC of the renal pelvis or proximal ureter and short-term complications after radical nephroureterectomy (RNU) with lymph node dissection (LND).Design, setting, and participants: This was a prospective Nordic multicenter study (four university hospitals, two county hospitals). Patients with clinically suspected locally advanced UTUC (stage >T1) and/or clinical lymph node–positive (cN+) disease were invited to participate. Participants underwent RNU and fractionated retroperitoneal LND using predefined side-specific templates.Outcome measurements and statistical analysis: The location of LNMs in the LND specimen and retroperitoneal lymph node recurrences during follow-up was recorded. Postoperative complications within 90 d of surgery were ascertained from patient charts. Descriptive statistics were used.Results and limitations: LNMs were present in the LND specimen in 23/100 patients, and nine of 100 patients experienced a retroperitoneal recurrence. Distribution per side revealed LNMs in the LND specimen in 11/38 (29%) patients with right-sided tumors, for whom the anatomically larger, right-sided template was used, in comparison to 12/62 (19%) patients with left-sided tumors, for whom a more limited template was used. High-grade complications (Clavien grade ≥3) within 90 d of surgery were registered for 13/100 patients. The study is limited in size and not powered to assess survival estimates.Conclusions: The suggested templates that we prospectively applied for right-sided and left-sided LND in patients with advanced UTUC included the majority of LNMs. High-grade complications directly related to the LND part of the surgery were limited.Patient summary: This study describes the location of lymph node metastases in patients with cancer in the upper urinary tract who underwent surgery to remove the affected kidney and ureter. The results show that most metastases occur within the template maps for lymph node surgery that we investigated, and that this surgery can be performed with few severe complications.
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| 6. |
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| 7. |
- Mårtensson, Annica
(författare)
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A Study of the Surrogate Light chain
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis has investigated the importance of the VpreB1 protein in early B cell development. Mice lacking the VpreB1 protein showed normal numbers of peripheral mature B cells. The number of B220 positive cells in the bone marrow was also normal, but the amounts of pre-BI cells was increased 2-fold and the numbers of pre-B II cells were reduced by 20%. In all other respects the lymphoid compartments were normal. The conclusion was that the VpreB1 protein is not necessary for the generation of B cells, and in the presence of the VpreB2 protein B lymphocytes develop normally and give rise to immuno competent cells in the periphery. In the second part of the thesis, the regulation of lambda5 and VpreB1 gene expression was investigated. A novel enhancer was isolated upstream of the VpreB1 gene and the core of the lambda5 enhancer was defined. Both enhancers contain elements that restrict reporter gene expression to pre-B cells when tested in cell lines. The transcription factors EBF and PEBP2 were shown to interact with both enhancers in EMSAs. These binding sites were crucial for lambda5 enhancer activity but less so for the VpreB1 enhancer. An E-box, potentially binding products of the E2A gene, E47 or E12, was shown to be functionally important for the lambda5 enhancer. In addition, the proto-oncogene c-myb was shown to interact with a functionally important element in the lamba5 core enhancer.
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| 8. |
- Struthers, Hamish, et al.
(författare)
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The effect of sea ice loss on sea salt aerosol concentrations and the = diative balance in the Arctic
- 2011
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Ingår i: ATMOSPHERIC CHEMISTRY AND PHYSICS. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:7, s. 3459-3477
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Tidskriftsartikel (refereegranskat)abstract
- Understanding Arctic climate change requires knowledge of both the external and the local drivers of Arctic climate as well as local feedbacks within the system. An Arctic feedback mechanism relating changes in sea ice extent to an alteration of the emission of sea salt aerosol and the consequent change in radiative balance is examined. A set of idealized climate model simulations were performed to quantify the radiative effects of changes in sea salt aerosol emissions induced by prescribed changes in sea ice extent. The model was forced using sea ice concentrations consistent with present day conditions and projections of sea ice extent for 2100. Sea salt aerosol emissions increase in response to a decrease in sea ice, the model results showing an annual average increase in number emission over the polar cap (70-90 degrees N) of 86 x 10(6) m(-2) s(-1) (mass emission increase of 23 mu g m(-2) s(-1)). This in turn leads to an increase in the natural aerosol optical depth of approximately 23%. In response to changes in aerosol optical depth, the natural component of the aerosol direct forcing over the Arctic polar cap is estimated to be between -0.2 and -0.4 W M(-2) for the summer months, which results in a negative feedback on the system. The model predicts that the change in first indirect aerosol effect (cloud albedo effect) is approximately a factor of ten greater than the change in direct aerosol forcing although this result is highly uncertain due to the crude representation of Arctic clouds and aerosol-cloud interactions in the model. This study shows that both the natural aerosol direct and first indirect effects are strongly dependent on the surface albedo, highlighting the strong coupling between sea ice, aerosols, Arctic clouds and their radiative effects.
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| 9. |
- Wennerstrand, Patricia, et al.
(författare)
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In vitro Protein Stability of Two Naturally Occurring Thiopurine S-methyltransferase Sequence Variants : Biophysical Characterization of TPMT*6 and TPMT*8
- 2017
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 2:8, s. 4991-4999
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Tidskriftsartikel (refereegranskat)abstract
- Thiopurine S-methyltransferase (TPMT) is a polymorphic enzyme involved in the metabolism and inactivation of thiopurine substances administered as immunosuppressants in the treatment of malignancies and autoimmune diseases. In this study, the naturally occurring variants, TPMT*6 (Y180F) and TPMT*8 (R215H), have been biophysically characterized. Despite being classified as low and intermediate in vivo enzyme activity variants, respectively, our results demonstrate a discrepancy because both TPMT*6 and TPMT*8 were found to exhibit normal functionality in vitro. While TPMT*8 exhibited biophysical properties almost indistinguishable from those of TPMTwt, the TPMT*6 variant was found to be destabilized. Furthermore, the contributions of the cofactor S-adenosylmethionine (SAM) to the thermodynamic stability of TPMT were investigated, but only a modest stabilizing effect was observed. Also presented herein is a new method for studies of the biophysical characteristics of TPMT and its variants using the extrinsic fluorescent probe 8-anilinonaphthalene-1-sulfonic acid (ANS). ANS was found to bind strongly to all investigated TPMT variants with a Kd of approximately 0.2 μM and a 1:1 binding ratio as determined by isothermal titration calorimetry (ITC). Circular dichroism and fluorescence measurements showed that ANS binds exclusively to the native state of TPMT, and binding to the active site was confirmed by molecular modeling and simulated docking as well as ITC measurements. The strong binding of the probe to native TPMT and the conformity of the obtained results demonstrate the advantages of using ANS binding characteristics in studies of this protein and its variants.
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| 10. |
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