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1.
Ann Rheum Dis ; 77(1): 111-118, 2018 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-28970207

RESUMEN

OBJECTIVES: To determine the 5-year outcomes of early remission induction therapy followed by targeted treatment aimed at drug-free remission (DFR) in patients with early arthritis. METHODS: In 12 hospitals, 610 patients with early (<2 years) rheumatoid arthritis (RA) or undifferentiated arthritis (UA) started on methotrexate (MTX) 25 mg/week and prednisone (60 mg/day tapered to 7.5 mg/day). Patients not in early remission (Disease Activity Score <1.6 after 4 months) were randomised (single blind) to arm 1, adding hydroxychloroquine 400 mg/day and sulfasalazine 2000 mg/day, or arm 2, switching to MTX plus adalimumab 40 mg/2 weeks. Treatment adjustments over time aimed at DFR. Outcomes were remission percentages, functional ability, toxicity and radiological damage progression after 5 years. RESULTS: After 4 months, 387 patients were in early remission, 83 were randomised to arm 1 and 78 to arm 2. After 5 years, 295/610 (48%) patients were in remission, 26% in sustained DFR (SDFR) (≥1 year) (220/387 (57%) remission and 135/387 (35%) SDFR in the early remission group, 50% remission, 11% SDFR in the randomisation arms without differences between the arms). More patients with UA (37% vs 23% RA, p=0.001) and more anticitrullinated protein antibody (ACPA)-negative patients (37% vs 18% ACPA-positive, p<0.001) achieved SDFR.Overall, mean Health Assessment Questionnaire was 0.6 (0.5), and median (IQR) damage progression was 0.5 (0-2.7) Sharp/van der Heijde points, with only five patients showing progression >25 points in 5 years. CONCLUSIONS: Five years of DFR-steered treatment in patients with early RA resulted in almost normal functional ability without clinically relevant joint damage across treatment groups. Patients who achieved early remission had the best clinical outcomes. There were no differences between the randomisation arms. SDFR is a realistic treatment goal.


Asunto(s)
Antirreumáticos/administración & dosificación , Artritis Reumatoide/tratamiento farmacológico , Articulaciones/diagnóstico por imagen , Radiografía , Índice de Severidad de la Enfermedad , Adalimumab/administración & dosificación , Adulto , Anciano , Artritis/diagnóstico por imagen , Artritis/tratamiento farmacológico , Artritis/patología , Artritis Reumatoide/diagnóstico por imagen , Artritis Reumatoide/patología , Progresión de la Enfermedad , Esquema de Medicación , Quimioterapia Combinada , Femenino , Humanos , Hidroxicloroquina/administración & dosificación , Masculino , Metotrexato/administración & dosificación , Persona de Mediana Edad , Prednisona/administración & dosificación , Inducción de Remisión , Método Simple Ciego , Sulfasalazina/administración & dosificación , Factores de Tiempo , Resultado del Tratamiento
2.
Med Mycol Case Rep ; 16: 16-19, 2017 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-28409094

RESUMEN

Invasive aspergillosis due to azole-resistant Aspergillus fumigatus is difficult to manage. We describe a case of azole-resistant invasive aspergillosis in a female bottlenose dolphin, who failed to respond to voriconazole and posaconazole therapy. As intravenous therapy was precluded, high dose posaconazole was initiated aimed at achieving trough levels exceeding 3 mg/l. Posaconazole serum levels of 3-9.5 mg/l were achieved without significant side-effects. Follow-up bronchoscopy and computed tomography showed complete resolution of the lesions.

3.
Rheumatology (Oxford) ; 55(12): 2138-2147, 2016 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-27581208

RESUMEN

OBJECTIVE: To evaluate direct and indirect costs per quality adjusted life year (QALY) for different initial treatment strategies in very early RA. METHODS: The 1-year data of the treatment in the Rotterdam Early Arthritis Cohort trial were used. Patients with a high probability (>70%) according to their likelihood of progressing to persistent arthritis, based on the prediction model of Visser, were randomized into one of following initial treatment strategies: (A) initial triple DMARD therapy (iTDT) with glucocorticoids (GCs) intramuscular (n = 91); (B) iTDT with an oral GC tapering scheme (n = 93); and (C) initial MTX monotherapy (iMM) with GCs similar to B (n = 97). Data on QALYs, measured with the Dutch EuroQol, and direct and indirect cost were used. Direct costs are costs of treatment and medical consumption, whereas indirect costs are costs due to loss of productivity. RESULTS: Average QALYs (sd) for A, B and C were, respectively, 0.75 (0.12), 0.75 (0.10) and 0.73 (0.13) for Dutch EuroQol. Highest total costs per QALY (sd) were, respectively, €12748 (€18767), €10 380 (€15 608) and €17 408 (€21 828) for strategy A, B and C (P = 0.012, B vs C). Direct as well as indirect costs were higher with iMM (strategy C) compared with iTDT (strategy B). Higher direct costs were due to ∼40% more biologic usage over time. Higher indirect costs, on the other hand, were caused by more long-term sickness and reduction in contract hours. iTDT was >95% cost-effective across all willingness-to-pay thresholds compared with iMM. CONCLUSION: iTDT was more cost-effective and had better worker productivity compared with iMM.


Asunto(s)
Antirreumáticos/economía , Artritis Reumatoide/economía , Metotrexato/economía , Administración Oral , Antirreumáticos/administración & dosificación , Artritis Reumatoide/tratamiento farmacológico , Análisis Costo-Beneficio , Esquema de Medicación , Costos de los Medicamentos , Quimioterapia Combinada/economía , Femenino , Gastos en Salud , Humanos , Masculino , Metotrexato/administración & dosificación , Persona de Mediana Edad , Años de Vida Ajustados por Calidad de Vida , Método Simple Ciego , Resultado del Tratamiento
4.
Ann Intern Med ; 164(8): 523-31, 2016 Apr 19.
Artículo en Inglés | MEDLINE | ID: mdl-27089068

RESUMEN

BACKGROUND: Treat-to-target therapy is effective for patients with rheumatoid arthritis (RA), but long-term results of continued targeted treatment are lacking. OBJECTIVE: To evaluate long-term outcomes in patients with early RA after 10 years of targeted treatment in 4 treatment strategies. DESIGN: Randomized trial. (Nederlands Trial Register: NTR262 and NTR265). SETTING: The Netherlands. PATIENTS: 508 patients with early active RA. INTERVENTION: Sequential monotherapy (strategy 1), step-up combination therapy (strategy 2), or initial combination therapy with prednisone (strategy 3) or with infliximab (strategy 4), all followed by targeted treatment aiming at low disease activity. MEASUREMENTS: Functional ability (Health Assessment Questionnaire [HAQ] score) and radiographic progression (Sharp-van der Heijde score) were primary end points. Survival in the study population was compared with the general population using the standardized mortality ratio. RESULTS: 195 of 508 of patients (38%) dropped out of the study (28% in strategy 4 vs. 40% to 45% in strategies 1 to 3, respectively). At year 10, mean HAQ score (SD) was 0.57 (0.56); 53% and 14% of patients were in remission and drug-free remission, respectively, without differences among the strategies. Over 10 years, mean HAQ scores were 0.69, 0.72, 0.64, and 0.58 in strategies 1 to 4, respectively (differences not clinically relevant). Radiographic damage was limited for all strategies, with mean Sharp-van der Heijde estimates during follow-up of 11, 8, 8, and 6 in strategies 1 to 4, respectively (P = 0.15). Standardized mortality ratio was 1.16 (95% CI, 0.92 to 1.46) based on 72 observed and 62 expected deaths, with similar survival among the 4 strategies (P = 0.81). LIMITATION: Dropout rate varied by strategy. CONCLUSION: In patients with early RA, initial (temporary) combination therapy results in faster clinical improvement and targeted treatment determines long-term outcomes. Drug-free remission, with prevention of functional deterioration and clinically relevant radiographic damage, and normalized survival are realistic outcomes. PRIMARY FUNDING SOURCE: Dutch College of Health Insurance Companies, Schering-Plough, and Janssen.


Asunto(s)
Anticuerpos Monoclonales/uso terapéutico , Antirreumáticos/uso terapéutico , Artritis Reumatoide/tratamiento farmacológico , Infliximab/uso terapéutico , Prednisona/uso terapéutico , Anticuerpos Monoclonales/administración & dosificación , Anticuerpos Monoclonales/efectos adversos , Antirreumáticos/administración & dosificación , Antirreumáticos/efectos adversos , Artritis Reumatoide/mortalidad , Progresión de la Enfermedad , Quimioterapia Combinada , Femenino , Estudios de Seguimiento , Humanos , Infliximab/administración & dosificación , Infliximab/efectos adversos , Masculino , Persona de Mediana Edad , Prednisona/administración & dosificación , Prednisona/efectos adversos , Inducción de Remisión , Análisis de Supervivencia , Resultado del Tratamiento
5.
Arthritis Res Ther ; 18: 23, 2016 Jan 21.
Artículo en Inglés | MEDLINE | ID: mdl-26794605

RESUMEN

BACKGROUND: Early suppression of disease activity in (rheumatoid) arthritis (RA) patients may result in drug-free remission and prevent damage. We assessed 2-year clinical and radiological outcomes of two disease activity score (DAS)-remission-steered treatment strategies in early arthritis patients. METHODS: Patients (n = 610) with early RA or undifferentiated arthritis (UA) were treated with methotrexate (MTX) and tapered high dose of prednisone. Patients in early remission (44/53 joints DAS <1.6) after 4 months tapered and stopped medication. Patients who did not achieve early DAS-remission were randomized to either MTX plus hydroxychloroquine plus sulphasalazine plus low dose prednisone (arm 1) or to MTX + adalimumab (arm 2). At four-monthly intervals, medication was tapered and stopped if DAS was <1.6 but restarted, increased or switched if DAS was ≥1.6. Proportions of (drug-free) DAS-remission (DFR) after 2 years and Sharp-van der Heijde scores (SHS) were analyzed separately for the treatment strategies and patients with RA and UA. RESULTS: After 2 years, 301/610 (49 %) patients were in DAS-remission and 131/610 (21 %) in DFR. In the early remission group 241/387 patients (62 %) were in DAS-remission and 111/387 (29 %) DFR. In arm 1 22/83 (27 %) and in arm 2 24/78 (31 %) were in DAS-remission, and 6/83 (7 %) and 7/78 (9 %), respectively, were in DFR. RA and UA patients achieved DAS-remission in comparable percentages (RA: 234/479 (49 %), UA: 64/122 (52 %), p = 0.25). More UA patients achieved DFR (41/122 (34 %)) compared to RA patients (89/479 (19 %), p<0.001). Mean (SD) DAS over time was 1.74 (0.58) across all patients, and median (IQR) SHS progression was 0 (0-0). CONCLUSIONS: After 2 years remission-steered treatment in early RA and UA patients, DAS-remission and DFR percentages were relatively low. Patients who achieved early remission more often achieved (drug-free) remission after 2 years than patients who needed additional treatment steps in the randomization arms, and more UA than RA patients achieved DFR. Overall, disease activity and radiologic damage progression in all patients were well suppressed. TRIAL REGISTRATION: http://www.controlled-trials.com/ISRCTN11916566 Registered 07/11/2006 and EudraCT number 2006-06186-16 Registered 16/07/2007.


Asunto(s)
Antirreumáticos/uso terapéutico , Artritis Reumatoide/diagnóstico , Artritis Reumatoide/terapia , Progresión de la Enfermedad , Índice de Severidad de la Enfermedad , Adulto , Anciano , Diagnóstico Precoz , Femenino , Humanos , Hidroxicloroquina/uso terapéutico , Masculino , Metotrexato/uso terapéutico , Persona de Mediana Edad , Inducción de Remisión , Método Simple Ciego , Sulfasalazina/uso terapéutico , Factores de Tiempo , Resultado del Tratamiento
6.
Rheumatology (Oxford) ; 55(4): 636-9, 2016 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-26538422

RESUMEN

OBJECTIVE: In this study we aimed to evaluate the effect of lowering the cut point of the 2010 criteria to identify more patients with RA among early inflammatory arthritis patients. METHODS: We included early arthritis patients from the Rotterdam Early Arthritis Cohort with at least one joint with clinical synovitis and symptoms for <1 year, with no other explanation for their symptoms. The demographic and clinical characteristics of each patient were recorded at baseline. Patients were classified as case or non-case at the 1-year follow-up by the definition used in the development of the 2010 criteria (MTX initiation). To assess the diagnostic performance of the 2010 criteria, the sensitivity and specificity at each cut point were determined. RESULTS: We included 557 patients in our analysis. At the 1-year follow-up, 253 patients (45%) were classified as case (MTX use). In the group of patients who scored 0-5 points (n = 328), 98 patients (30%) were classified as case (MTX use). The sensitivity and specificity of the 2010 criteria using the cut point of 6 were 61% and 76%, respectively. With the cut point of 5, the sensitivity would increase to 76% and the specificity would decrease to 68%. CONCLUSION: By lowering the cut point of the 2010 criteria from 6 to 5 points, we were able to identify 15% more RA patients at the cost of 8% more false-positive patients.


Asunto(s)
Artritis Reumatoide/diagnóstico , Índice de Severidad de la Enfermedad , Adulto , Anciano , Antirreumáticos/uso terapéutico , Artritis Reumatoide/tratamiento farmacológico , Estudios de Cohortes , Diagnóstico Precoz , Reacciones Falso Positivas , Femenino , Estudios de Seguimiento , Humanos , Masculino , Metotrexato/uso terapéutico , Persona de Mediana Edad , Sensibilidad y Especificidad
7.
Ann Rheum Dis ; 71(9): 1472-7, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22402145

RESUMEN

AIM: Classifying more patients as rheumatoid arthritis (RA) (2010 American College of Rheumatology/European League Against Rheumatism criteria for RA) may improve treatment outcomes but may cause overtreatment in daily practice. The authors determined the efficacy of initial methotrexate (MTX) plus prednisone treatment in patients with 1987 or 2010 classified RA and undifferentiated arthritis (UA). METHOD: 610 recent onset RA or UA patients started with MTX 25 mg/week and prednisone 60 mg/day tapered to 7.5 mg/day in 7 weeks. Percentage remissions after 4 months were compared between RA (1987 or 2010 criteria) and UA. Predictors for remission were identified. RESULTS: With the 2010 criteria, 19% more patients were classified as RA than with the 1987 criteria, but similar remission rates were achieved: 291/479 (61%) 2010 classified RA and 211/264 (58%) 1987 classified RA patients (p=0.52), and 79/122 (65%) UA patients (p=0.46). Anticitrullinated protein antibodies (ACPA) positive RA patients achieved more remission (66%) than ACPA negative RA patients (51%, p=0.001), but also had a lower mean baseline Disease Activity Score (DAS) (3.2 vs 3.6, p<0.001). Independent predictors for remission were male sex, low joint counts, DAS and Health Assessment Questionnaire, low body mass index and ACPA positivity. CONCLUSION: Initial treatment with MTX and a tapered high dose of prednisone results in similarly high remission percentages after 4 months (about 60%) in RA patients, regardless of fulfilling the 1987 or 2010 criteria, and in UA patients. Independent predictors indicate that initiating treatment while disease activity is relatively low results in more remission.


Asunto(s)
Antirreumáticos/uso terapéutico , Artritis/tratamiento farmacológico , Metotrexato/uso terapéutico , Prednisona/uso terapéutico , Antirreumáticos/administración & dosificación , Artritis/patología , Combinación de Medicamentos , Femenino , Humanos , Masculino , Metotrexato/administración & dosificación , Persona de Mediana Edad , Prednisona/administración & dosificación , Inducción de Remisión
8.
Arthritis Rheum ; 61(3): 291-9, 2009 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-19248130

RESUMEN

OBJECTIVE: To evaluate societal costs and quality-adjusted life years (QALYs) of treatment strategies for patients with recent-onset active rheumatoid arthritis (RA). METHODS: Patients (n = 508) were randomly allocated to 1 of 4 treatment strategy groups: sequential monotherapy, step-up combination therapy, initial combination therapy with prednisone, or initial combination therapy with infliximab. For 2 years, patients reported cost and utility measures. RESULTS: Average QALYs (ideally 2.00) for groups 1-4 were 1.29, 1.31, 1.32, and 1.41, respectively, for the British EuroQol (P

Asunto(s)
Antirreumáticos/administración & dosificación , Antirreumáticos/economía , Artritis Reumatoide/tratamiento farmacológico , Artritis Reumatoide/economía , Costos de la Atención en Salud , Adulto , Anciano , Anticuerpos Monoclonales/administración & dosificación , Análisis Costo-Beneficio , Esquema de Medicación , Quimioterapia Combinada , Femenino , Humanos , Infliximab , Masculino , Persona de Mediana Edad , Prednisona/administración & dosificación , Años de Vida Ajustados por Calidad de Vida
9.
Ann Intern Med ; 146(6): 406-15, 2007 Mar 20.
Artículo en Inglés | MEDLINE | ID: mdl-17371885

RESUMEN

BACKGROUND: In patients with early rheumatoid arthritis, initial combination therapies provide earlier clinical improvement and less progression of joint damage after 1 year compared with initial monotherapies (as demonstrated in the BeSt study). OBJECTIVE: To evaluate whether the initial clinical and radiographic efficacy of combination therapies could be maintained during the second year of follow-up in patients with early rheumatoid arthritis. DESIGN: Randomized, controlled clinical trial with blinded assessors. SETTING: 18 peripheral and 2 university medical centers in the Netherlands. PATIENTS: 508 patients with early active rheumatoid arthritis. INTERVENTION: Sequential monotherapy (group 1), step-up combination therapy (group 2), initial combination therapy with tapered high-dose prednisone (group 3), or initial combination therapy with infliximab (group 4). Trimonthly treatment adjustments were made to achieve low disease activity. MEASUREMENTS: Primary end points were functional ability (Health Assessment Questionnaire) and Sharp-van der Heijde score for radiographic joint damage. RESULTS: Groups 3 and 4 had more rapid clinical improvement during the first year; all groups improved further to a mean functional ability score of 0.6 (overall, P = 0.257) and 42% were in remission (overall, P = 0.690) during the second year. Progression of joint damage remained better suppressed in groups 3 and 4 (median scores of 2.0, 2.0, 1.0, and 1.0 in groups 1, 2, 3, and 4, respectively [P = 0.004]). After 2 years, 33%, 31%, 36%, and 53% of patients in groups 1 through 4, respectively, were receiving single-drug therapy for initial treatment. There were no significant differences in toxicity. LIMITATIONS: Patients and physicians were aware of the allocated group, and the assessors were blinded. CONCLUSIONS: Currently available antirheumatic drugs can be highly effective in patients with early rheumatoid arthritis in a setting of tight disease control. Initial combination therapies seem to provide earlier clinical improvement and less progression of joint damage, but all treatment strategies eventually showed similar clinical improvements. In addition, combination therapy can be withdrawn successfully and less treatment adjustments are needed than with initial monotherapies.


Asunto(s)
Antirreumáticos/uso terapéutico , Artritis Reumatoide/tratamiento farmacológico , Antiinflamatorios/efectos adversos , Antiinflamatorios/uso terapéutico , Anticuerpos Monoclonales/efectos adversos , Anticuerpos Monoclonales/uso terapéutico , Antirreumáticos/efectos adversos , Artritis Reumatoide/diagnóstico por imagen , Esquema de Medicación , Quimioterapia Combinada , Humanos , Infliximab , Prednisona/efectos adversos , Prednisona/uso terapéutico , Radiografía , Método Simple Ciego , Resultado del Tratamiento
10.
Proc Natl Acad Sci U S A ; 98(15): 8219-26, 2001 Jul 17.
Artículo en Inglés | MEDLINE | ID: mdl-11459956

RESUMEN

The unwinding of the parental DNA duplex during replication causes a positive linking number difference, or superhelical strain, to build up around the elongating replication fork. The branching at the fork and this strain bring about different conformations from that of (-) supercoiled DNA that is not being replicated. The replicating DNA can form (+) precatenanes, in which the daughter DNAs are intertwined, and (+) supercoils. Topoisomerases have the essential role of relieving the superhelical strain by removing these structures. Stalled replication forks of molecules with a (+) superhelical strain have the additional option of regressing, forming a four-way junction at the replication fork. This four-way junction can be acted on by recombination enzymes to restart replication. Replication and chromosome folding are made easier by topological domain barriers, which sequester the substrates for topoisomerases into defined and concentrated regions. Domain barriers also allow replicated DNA to be (-) supercoiled. We discuss the importance of replicating DNA conformations and the roles of topoisomerases, focusing on recent work from our laboratory.


Asunto(s)
Replicación del ADN , Conformación de Ácido Nucleico , ADN Superhelicoidal/química , Plásmidos/química
11.
Proc Natl Acad Sci U S A ; 97(26): 14674-9, 2000 Dec 19.
Artículo en Inglés | MEDLINE | ID: mdl-11121068

RESUMEN

Nitrogen regulatory protein C (NtrC) of enteric bacteria activates transcription of genes/operons whose products minimize the slowing of growth under nitrogen-limiting conditions. To reveal the NtrC regulon of Escherichia coli we compared mRNA levels in a mutant strain that overexpresses NtrC-activated genes [glnL(Up)] to those in a strain with an ntrC (glnG) null allele by using DNA microarrays. Both strains could be grown under conditions of nitrogen excess. Thus, we could avoid differences in gene expression caused by slow growth or nitrogen limitation per se. Rearranging the spot images from microarrays in genome order allowed us to detect all of the operons known to be under NtrC control and facilitated detection of a number of new ones. Many of these operons encode transport systems for nitrogen-containing compounds, including compounds recycled during cell-wall synthesis, and hence scavenging appears to be a primary response to nitrogen limitation. In all, approximately 2% of the E. coli genome appears to be under NtrC control, although transcription of some operons depends on the nitrogen assimilation control protein, which serves as an adapter between NtrC and final sigma(70)-dependent promoters.


Asunto(s)
Proteínas Bacterianas/genética , Proteínas de Unión al ADN/genética , Proteínas de Escherichia coli , Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica , Nitrógeno/metabolismo , Transactivadores/genética , Fusión Artificial Génica , Fraccionamiento Químico , Escherichia coli/metabolismo , Genes Bacterianos , Operón Lac , Análisis de Secuencia por Matrices de Oligonucleótidos/métodos , Proteínas PII Reguladoras del Nitrógeno , Periplasma/metabolismo , Fosfoproteínas Fosfatasas/genética , Proteínas Quinasas/genética , Factores de Transcripción/genética
12.
Proc Natl Acad Sci U S A ; 97(22): 12170-5, 2000 Oct 24.
Artículo en Inglés | MEDLINE | ID: mdl-11027315

RESUMEN

We investigated the global changes in mRNA abundance in Escherichia coli elicited by various perturbations of tryptophan metabolism. To do so we printed DNA microarrays containing 95% of all annotated E. coli ORFs. We determined the expression profile that is predominantly dictated by the activity of the tryptophan repressor. Only three operons, trp, mtr, and aroH, exhibited appreciable expression changes consistent with this profile. The quantitative changes we observed in mRNA levels for the five genes of the trp operon were consistent within a factor of 2, with expectations based on established Trp protein levels. Several operons known to be regulated by the TyrR protein, aroF-tyrA, aroL, aroP, and aroG, were down-regulated on addition of tryptophan. TyrR can be activated by any one of the three aromatic amino acids. Only one operon, tnaAB, was significantly activated by the presence of tryptophan in the medium. We uncovered a plethora of likely indirect effects of changes in tryptophan metabolism on intracellular mRNA pools, most prominent of which was the sensitivity of arginine biosynthetic operons to tryptophan starvation.


Asunto(s)
Escherichia coli/metabolismo , Perfilación de la Expresión Génica , Triptófano/metabolismo , Escherichia coli/genética , Familia de Multigenes , Operón , ARN Mensajero/genética , Proteínas Represoras/genética , Triptófano/genética
13.
Proc Natl Acad Sci U S A ; 97(17): 9419-24, 2000 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-10944214

RESUMEN

We used DNA microarrays of the Escherichia coli genome to trace the progression of chromosomal replication forks in synchronized cells. We found that both DNA gyrase and topoisomerase IV (topo IV) promote replication fork progression. When both enzymes were inhibited, the replication fork stopped rapidly. The elongation rate with topo IV alone was 1/3 of normal. Genetic data confirmed and extended these results. Inactivation of gyrase alone caused a slow stop of replication. Topo IV activity was sufficient to prevent accumulation of (+) supercoils in plasmid DNA in vivo, suggesting that topo IV can promote replication by removing (+) supercoils in front of the chromosomal fork.


Asunto(s)
Replicación del ADN , ADN-Topoisomerasas de Tipo II/metabolismo , ADN Bacteriano/biosíntesis , Escherichia coli/enzimología , Escherichia coli/genética , Análisis de Secuencia por Matrices de Oligonucleótidos , Replicación del ADN/efectos de los fármacos , Topoisomerasa de ADN IV , ADN-Topoisomerasas de Tipo II/genética , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Superhelicoidal/biosíntesis , ADN Superhelicoidal/química , ADN Superhelicoidal/genética , Escherichia coli/efectos de los fármacos , Genoma Bacteriano , Cinética , Movimiento/efectos de los fármacos , Mutación/genética , Novobiocina/farmacología , Plásmidos/biosíntesis , Plásmidos/química , Plásmidos/genética , Inhibidores de Topoisomerasa II
14.
Bioessays ; 21(10): 805-8, 1999 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-10497329

RESUMEN

DNA replication requires the unwinding of the parental duplex, which generates (+) supercoiling ahead of the replication fork. It has been thought that removal of these (+) supercoils was the only method of unlinking the parental strands. Recent evidence implies that supercoils can diffuse across the replication fork, resulting in interwound replicated strands called precatenanes. Topoisomerases can then act both in front of and behind the replication fork. A new study by Sogo et al. [J Mol Biol 1999;286:637-643 (Ref. 1)], using a topological analysis, provides the best evidence that precatenanes exist in negatively supercoiled, partially replicated molecules in vivo.


Asunto(s)
Replicación del ADN/fisiología , ADN-Topoisomerasas de Tipo I/metabolismo , ADN Superhelicoidal/química , ADN Superhelicoidal/metabolismo , Modelos Biológicos , Conformación de Ácido Nucleico
15.
J Mol Biol ; 289(4): 747-75, 1999 Jun 18.
Artículo en Inglés | MEDLINE | ID: mdl-10369759

RESUMEN

Bacteriophage lambda integrase (Int) is a versatile site-specific recombinase. In concert with other proteins, it mediates phage integration into and excision out of the bacterial chromosome. Int recombines intramolecular sites in inverse or direct orientation or sites on separate DNA molecules. This wide spectrum of Int-mediated reactions has, however, hindered our understanding of the topology of Int recombination. By systematically analyzing the topology of Int reaction products and using a mathematical method called tangles, we deduce a unified model for Int recombination. We find that, even in the absence of (-) supercoiling, all Int reactions are chiral, producing one of two possible enantiomers of each product. We propose that this chirality reflects a right-handed DNA crossing within or between recombination sites in the synaptic complex that favors formation of right-handed Holliday junction intermediates. We demonstrate that the change in linking number associated with excisive inversion with relaxed DNA is equally +2 and -2, reflecting two different substrates with different topology but the same chirality. Additionally, we deduce that integrative Int recombination differs from excisive recombination only by additional plectonemic (-) DNA crossings in the synaptic complex: two with supercoiled substrates and one with relaxed substrates. The generality of our results is indicated by our finding that two other members of the integrase superfamily of recombinases, Flp of yeast and Cre of phage P1, show the same intrinsic chirality as lambda Int.


Asunto(s)
Bacteriófago lambda/enzimología , Integrasas/metabolismo , Recombinación Genética , Proteínas Virales , Bacteriófago P1/enzimología , Inversión Cromosómica , ADN Nucleotidiltransferasas/metabolismo , Integrasas/química , Modelos Biológicos , Conformación Proteica , Especificidad por Sustrato , Integración Viral
16.
Genetica ; 106(1-2): 131-40, 1999.
Artículo en Inglés | MEDLINE | ID: mdl-10710719

RESUMEN

This article is a perspective on the separation of the complementary strands of DNA during replication. Given the challenges of DNA strand separation and its vital importance, it is not surprising that cells have developed many strategies for promoting unlinking. We summarize seven different factors that contribute to strand separation and chromosome segregation. These are: (1) supercoiling promotes unlinking by condensation of DNA; (2) unlinking takes place throughout a replicating domain by the complementary action of topoisomerases on precatenanes and supercoils; (3) topological domains isolate the events near the replication fork and permit the supercoiling-dependent condensation of partially replicated DNA; (4) type-II topoisomerases use ATP to actively unlink DNA past the equilibrium position; (5) the effective DNA concentration in vivo is less than the global DNA concentration; (6) mechanical forces help unlink chromosomes; and (7) site-specific recombination promotes unlinking at the termination of replication by resolving circular dimeric chromosomes.


Asunto(s)
Replicación del ADN/fisiología , Segregación Cromosómica , ADN Helicasas/metabolismo , ADN-Topoisomerasas de Tipo I/metabolismo , ADN Bacteriano/fisiología , ADN Superhelicoidal/fisiología , Recombinación Genética
17.
Cell ; 94(6): 819-27, 1998 Sep 18.
Artículo en Inglés | MEDLINE | ID: mdl-9753328

RESUMEN

We studied the structure of replication intermediates accumulated by Tus-induced arrest of plasmid DNA replication at termination sites. For intermediates generated both in vitro with purified components and in vivo, superhelical stress is distributed throughout the entire partially replicated molecule; daughter DNA segments are wound around each other, and the unreplicated region is supercoiled. Thus, unlinking of parental DNA strands by topoisomerases can be carried out both behind and in front of the replication fork. We explain why previous studies with prokaryotic and eukaryotic replication intermediates discerned only supercoiling in the unreplicated portion.


Asunto(s)
Replicación del ADN/genética , ADN Superhelicoidal/química , ADN Superhelicoidal/ultraestructura , Electroforesis en Gel de Agar , Escherichia coli , Isomerismo , Microscopía Electrónica , Conformación de Ácido Nucleico , Plásmidos/química , Plásmidos/ultraestructura
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