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- Farge, G., et al.
(author)
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Protein sliding and DNA denaturation are essential for DNA organization by human mitochondrial transcription factor A
- 2012
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 3
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Journal article (peer-reviewed)abstract
- Mitochondria organize their genome in protein-DNA complexes called nucleoids. The mitochondrial transcription factor A (TFAM), a protein that regulates mitochondrial transcription, is abundant in these nucleoids. TFAM is believed to be essential for mitochondrial DNA compaction, yet the exact mechanism has not been resolved. Here we use a combination of single-molecule manipulation and fluorescence microscopy to show the nonspecific DNA-binding dynamics and compaction by TFAM. We observe that single TFAM proteins diffuse extensively over DNA (sliding) and, by collisions, form patches on DNA in a cooperative manner. Moreover, we demonstrate that TFAM induces compaction by changing the flexibility of the DNA, which can be explained by local denaturation of the DNA (melting). Both sliding of TFAM and DNA melting are also necessary characteristics for effective, specific transcription regulation by TFAM. This apparent connection between transcription and DNA organization clarifies how TFAM can accomplish two complementary roles in the mitochondrial nucleoid at the same time.
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| 3. |
- Farge, G., et al.
(author)
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In Vitro-Reconstituted Nucleoids Can Block Mitochondrial DNA Replication and Transcription
- 2014
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In: Cell Reports. - : Elsevier BV. - 2211-1247. ; 8:1, s. 66-74
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Journal article (peer-reviewed)abstract
- The mechanisms regulating the number of active copies of mtDNA are still unclear. A mammalian cell typically contains 1,000-10,000 copies of mtDNA, which are packaged into nucleoprotein complexes termed nucleoids. The main protein component of these structures is mitochondrial transcription factor A (TFAM). Here, we reconstitute nucleoid-like particles in vitro and demonstrate that small changes in TFAM levels dramatically impact the fraction of DNA molecules available for transcription and DNA replication. Compaction by TFAM is highly cooperative, and at physiological ratios of TFAM to DNA, there are large variations in compaction, from fully compacted nucleoids to naked DNA. In compacted nucleoids, TFAMforms stable protein filaments onDNAthat block melting and prevent progression of the replication and transcription machineries. Based on our observations, we suggest that small variations in the TFAM-to-mtDNA ratio may be used to regulate mitochondrial gene transcription and DNA replication.
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| 4. |
- Fransen, J., et al.
(author)
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Clinical prediction of 5-year survival in systemic sclerosis: validation of a simple prognostic model in EUSTAR centres
- 2011
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In: Annals of the Rheumatic Diseases. - : BMJ. - 1468-2060 .- 0003-4967. ; 70:10, s. 1788-1792
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Journal article (peer-reviewed)abstract
- Objective Systemic sclerosis (SSc) is associated with a significant reduction in life expectancy. A simple prognostic model to predict 5-year survival in SSc was developed in 1999 in 280 patients, but it has not been validated in other patients. The predictions of a prognostic model are usually less accurate in other patients, especially from other centres or countries. A study was undertaken to validate the prognostic model to predict 5-year survival in SSc in other centres throughout Europe. Methods A European multicentre cohort of patients with SSc diagnosed before 2002 was established. Patients with SSc according to the preliminary American College of Rheumatology classification criteria were eligible for the study when they were followed for at least 5 years or shorter if they died. The primary outcome was 5-year survival after diagnosis of SSc. The predefined prognostic model uses the following baseline variables: age, gender, presence of urine protein, erythrocyte sedimentation rate (ESR) and carbon monoxide diffusing capacity (DLCO). Results Data were available for 1049 patients, 119 (11%) of whom died within 5 years after diagnosis. Of the patients, 85% were female, the mean (SD) age at diagnosis was 50 (14) years and 30% were classified as having diffuse cutaneous SSc. The prognostic model with age (OR 1.03), male gender (OR 1.93), urine protein (OR 2.29), elevated ESR (1.89) and low DLCO (OR 1.94) had an area under the receiver operating characteristic curve of 0.78. Death occurred in 12 (2.2%) of 509 patients with no risk factors, 45 (13%) of 349 patients with one risk factor, 55 (33%) of 168 patients with two risk factors and 7 (30%) of 23 patients with three risk factors. Conclusion A simple prognostic model using three disease factors to predict 5-year survival at diagnosis in SSc showed reasonable performance upon validation in a European multicentre study.
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| 5. |
- Uhler, Jay (Jennifer), et al.
(author)
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The UbL protein UBTD1 stably interacts with the UBE2D family of E2 ubiquitin conjugating enzymes
- 2014
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In: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 443:1, s. 7-12
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Journal article (peer-reviewed)abstract
- UBTD1 is a previously uncharacterized ubiquitin-like (UbL) domain containing protein with high homology to the mitochondrial Dc-UbP/UBTD2 protein. Here we show that UBTD1 and UBTD2 belong to a family of proteins that is conserved through evolution and found in metazoa, funghi, and plants. To gain further insight into the function of UBTD1, we screened for interacting proteins. In a yeast-2-hybrid (Y2H) screen, we identified several proteins involved in the ubiquitylation pathway, including the UBE2D family of E2 ubiquitin conjugating enzymes. An affinity capture screen for UBTD1 interacting proteins in whole cell extracts also identified members of the UBE2D family. Biochemical characterization of recombinant UBTD1 and UBE2D demonstrated that the two proteins form a stable, stoichiometric complex that can be purified to near homogeneity. We discuss the implications of these findings in light of the ubiquitin proteasome system (UPS). (C) 2013 Published by Elsevier Inc.
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| 6. |
- Alchi, B, et al.
(author)
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Autologous haematopoietic stem cell transplantation for systemic lupus erythematosus: data from the European Group for Blood and Marrow Transplantation registry
- 2013
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In: Lupus. - : SAGE Publications. - 1477-0962 .- 0961-2033. ; 22:3, s. 245-253
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Journal article (peer-reviewed)abstract
- Patients with systemic lupus erythematosus (SLE) refractory to conventional immunosuppression suffer substantial morbidity and mortality due to active disease and treatment toxicity. Immunoablation followed by autologous stem cell transplantation (ASCT) is a novel therapeutic strategy that potentially offers new hope to these patients. Methods This retrospective survey reviews the efficacy and safety of ASCT in 28 SLE patients from eight centres reported to the European Group for Blood and Marrow Transplantation (EBMT) registry between 2001 and 2008. Results Median disease duration before ASCT was 52 (nine to 396) months, 25/28 SLE patients (89%) were female, age 29 (16–48) years. At the time of ASCT, eight (one to 11) American College of Rheumatology (ACR) diagnostic criteria for SLE were present and 17 (60%) patients had nephritis. Peripheral blood stem cells were mobilized with cyclophosphamide and granulocyte-colony stimulating factor in 93% of patients, and ex vivo CD34 stem cell selection was performed in 36%. Conditioning regimens were employed with either low ( n = 10) or intermediate (18) intensities. With a median follow-up of 38 (one to 110) months after ASCT, the five-year overall survival was 81 ± 8%, disease-free survival was 29 ± 9%, relapse incidence (RI) was 56 ± 11% and non-relapse mortality was 15 ± 7%. Graft manipulation by CD34+ selection was associated with a lower RI ( p = 0.001) on univariate analysis. There were five deaths within two years after ASCT: three caused by infection, one by secondary autoimmune disease and one by progressive SLE. Conclusions Our data further support the concept of immunoablation and ASCT to re-induce long-term clinical and serologic remissions in refractory SLE patients even in the absence of maintenance therapy. This study also suggests a beneficial effect of ex vivo graft manipulation on prevention of relapses post-transplantation in SLE.
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| 8. |
- Atanassova, N, et al.
(author)
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Sequence-specific stalling of DNA polymerase gamma and the effects of mutations causing progressive ophthalmoplegia
- 2011
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In: Human Molecular Genetics. - 0964-6906. ; 20:6, s. 1212-1223
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Journal article (peer-reviewed)abstract
- A large number of mutations in the gene encoding the catalytic subunit of mitochondrial DNA polymerase γ (POLγA) cause human disease. The Y955C mutation is common and leads to a dominant disease with progressive external ophthalmoplegia and other symptoms. The biochemical effect of the Y955C mutation has been extensively studied and it has been reported to lower enzyme processivity due to decreased capacity to utilize dNTPs. However, it is unclear why this biochemical defect leads to a dominant disease. Consistent with previous reports, we show here that the POLγA:Y955C enzyme only synthesizes short DNA products at dNTP concentrations that are sufficient for proper function of wild-type POLγA. In addition, we find that this phenotype is overcome by increasing the dNTP concentration, e.g. dATP. At low dATP concentrations, the POLγA:Y955C enzyme stalls at dATP insertion sites and instead enters a polymerase/exonuclease idling mode. The POLγA:Y955C enzyme will compete with wild-type POLγA for primer utilization, and this will result in a heterogeneous population of short and long DNA replication products. In addition, there is a possibility that POLγA:Y955C is recruited to nicks of mtDNA and there enters an idling mode preventing ligation. Our results provide a novel explanation for the dominant mtDNA replication phenotypes seen in patients harboring the Y955C mutation, including the existence of site-specific stalling. Our data may also explain why mutations that disturb dATP pools can be especially deleterious for mtDNA synthesis.
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| 10. |
- Distler, J. H. W., et al.
(author)
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Is there a role for TNF-alpha antagonists in the treatment of SSc? EUSTAR expert consensus development using the Delphi technique
- 2011
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In: Clinical and Experimental Rheumatology. - 1593-098X. ; 29:2, s. 40-45
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Journal article (peer-reviewed)abstract
- Objective: To obtain experiences and expert opinion on treatment of SSc patients with TNF-alpha antagonists. Methods: An investigation was carried out among the EUSTAR centres into their expertise on use of TNF-alpha antagonists. Assessment forms on the frequency of TNF-alpha inhibitor use were distributed to EULAR Scleroderma Trials and Research Group (EUSTAR) centres. Afterwards, a three round Delphi exercise was performed to obtain expert consensus on the use of TNF-alpha inhibitors in SSc. Results: Seventy-nine centres returned information on use of TNF-alpha antagonists in SSc patients. A total of 65 patients were treated with TNF-alpha inhibitors in 14 different centres. Forty-eight of the 65 patients treated with TNF-alpha inhibitors improved. Improvement was mainly seen in patients with arthritis, whereas the effects on fibrosis varied. In the first round of the subsequent Delphi approach, 71 out of 79 experts stated that they would use TNF-alpha antagonists in SSc. Arthritis was suggested as an indication for TNF alpha antagonists by 75% of the experts. However; after the third stage of the Delphi exercise, the acceptance for the off-label use of TNF-alpha antagonists decreased and 59% recommended that TNF-alpha antagonists should not be used or only used in clinical trials in SSc patients, while 38% of the experts suggested the use of TNF-alpha antagonists for arthritis associated with SSc. Conclusions: Most of the experts do not recommend the routine use of TNF-alpha antagonists in systemic sclerosis. Arthritis might be a potential indication in SSc, although controlled clinical trials with TNF-alpha antagonists are needed before general recommendations can be given.
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