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2.
S Afr Med J ; 112(2b): 13486, 2021 12 24.
Article in English | MEDLINE | ID: mdl-35140006

ABSTRACT

Sisonke is a multicentre, open-label, single-arm phase 3B vaccine implementation study of healthcare workers (HCWs) in South Africa, with prospective surveillance for 2 years. The primary endpoint is the rate of severe COVID­19, including hospitalisations and deaths. The  Sisonke study enrolled and vaccinated participants nationally at potential vaccination roll-out sites between 17 February and 26 May 2021. After May 2021, additional HCWs were vaccinated as part of a sub-study at selected clinical research sites. We discuss 10 lessons learnt to strengthen national and global vaccination strategies:(i) consistently advocate for vaccination to reduce public hesitancy; (ii) an electronic vaccination data system (EVDS) is critical; (iii) facilitate access to a choice of vaccination sites, such as religious and community centres, schools, shopping malls and drive-through centres; (iv) let digitally literate people help elderly and marginalised people to register for vaccination; (v) develop clear 'how to' guides for vaccine storage, pharmacy staff and vaccinators; (vi) leverage instant messaging platforms, such as WhatsApp, for quick communication among staff at vaccination centres; (vii) safety is paramount - rapid health assessments are needed at vaccination centres to identify people at high risk of serious adverse events, including anaphylaxis or thrombosis with thrombocytopenia syndrome. Be transparent about adverse events and contextualise vaccination benefits, while acknowledging the small risks; (viii) provide real-time, responsive support to vaccinees post vaccination and implement an accessible national vaccine adverse events surveillance system; (ix) develop efficient systems to monitor and investigate COVID­19 breakthrough infections; and (x) flexibility and teamwork are essential in vaccination centres across national, provincial and district levels and between public and private sectors.


Subject(s)
COVID-19 Vaccines/administration & dosage , COVID-19/prevention & control , Health Personnel , Infectious Disease Transmission, Patient-to-Professional/prevention & control , Mass Vaccination , Humans , Prospective Studies , SARS-CoV-2 , South Africa/epidemiology , Vaccination Hesitancy
3.
Trop Med Int Health ; 25(12): 1450-1466, 2020 12.
Article in English | MEDLINE | ID: mdl-32985080

ABSTRACT

OBJECTIVE: To describe the receipt of a diagnosis, referral and treatment for depression in people receiving antiretroviral therapy (ART), with depressive symptoms and attending primary care clinics in South Africa, and investigate factors associated with receiving these components of care. METHODS: This is a secondary analysis of data from a randomised controlled trial of an intervention intended to improve detection and treatment of depression in primary care patients receiving ART. In this analysis, we combined cross-sectional and longitudinal data from the intervention and control arms. Using regression models and adjusting for intra-cluster correlation of outcomes, we investigated associations between socioeconomic characteristics, depressive symptoms, stress, disability and stigma, and receipt of a diagnosis, referral and treatment for depression. RESULTS: Of 2002 participants enrolled, 18% reported a previous diagnosis of depression by a healthcare worker and 10% reported having received counselling from a specialist mental health worker. Diagnosis, referral and counselling during the follow-up period were appropriately targeted, being independently more frequent in participants with higher enrolment scores for depressive symptoms, stress or disability. Participants with higher stigma scores at enrolment were independently less likely to receive counselling. Severe socio-economic deprivation was common but was not associated with treatment. CONCLUSION: While the receipt of a diagnosis, referral and treatment for depression were uncommon, they seemed to be appropriately targeted. Socio-economic deprivation was not associated with treatment.


OBJECTIF: Décrire la réception d'un diagnostic, de l'orientation et du traitement pour la dépression chez les personnes recevant un traitement antirétroviral (ART), présentant des symptômes dépressifs et fréquentant des cliniques de soins primaires en Afrique du Sud, et étudier les facteurs associés à la réception de ces éléments de soins. MÉTHODES: Il s'agit ici d'une analyse secondaire des données d'un essai contrôlé randomisé d'une intervention destinée à améliorer la détection et le traitement de la dépression chez les patients sous ART dans les soins primaires. Dans cette analyse, nous avons combiné les données transversales et longitudinales des bras d'intervention et témoin. En utilisant des modèles de régression et en ajustant la corrélation intra-grappes des résultats, nous avons étudié les associations entre les caractéristiques sociodémographiques, les symptômes dépressifs, le stress, l'invalidité et la stigmatisation, et la réception d'un diagnostic, d'une orientation et d'un traitement pour la dépression. RÉSULTATS: Sur 2.002 participants inscrits, 18% ont déclaré un diagnostic antérieur de dépression par un agent de santé et 10% ont déclaré avoir reçu des conseils d'un agent spécialisé pour la santé mentale. Le diagnostic, l'orientation et le conseil pendant la période de suivi ont été ciblés de manière appropriée, étant indépendamment plus fréquents chez les participants ayant des scores d'inscription plus élevés pour les symptômes dépressifs, le stress ou l'invalidité. Les participants ayant des scores de stigmatisation plus élevés à l'inscription étaient indépendamment moins susceptibles de recevoir des conseils. La privation socioéconomique sévère était courante mais n'était pas associée au traitement. CONCLUSION: Bien que la réception d'un diagnostic, l'orientation et le traitement de la dépression soient rares, ils semblaient bien ciblés. La privation socioéconomique n'était pas associée au traitement.


Subject(s)
Depression/diagnosis , Depression/therapy , HIV Infections/psychology , Primary Health Care , Referral and Consultation , Adult , Antirheumatic Agents/therapeutic use , Counseling , Cross-Sectional Studies , Depression/epidemiology , Female , HIV Infections/drug therapy , Humans , Logistic Models , Male , Middle Aged , Poverty , Social Stigma , South Africa/epidemiology
4.
Epidemiol Psychiatr Sci ; 29: e135, 2020 Jun 15.
Article in English | MEDLINE | ID: mdl-32536359

ABSTRACT

Against the backdrop of mounting calls for the global scaling-up of mental health services - including quality care and prevention services - there is very little guidance internationally on strategies for scaling-up such services. Drawing on lessons from scale-up attempts in six low- and middle-income countries, and using exemplars from the front-lines in South Africa, we illustrate how health reforms towards people-centred chronic disease management provide enabling policy window opportunities for embedding mental health scale-up strategies into these reforms. Rather than going down the oft-trodden road of vertical funding for scale-up of mental health services, we suggest using the policy window that stresses global policy shifts towards strengthening of comprehensive integrated primary health care systems that are responsive to multimorbid chronic conditions. This is indeed a substantial opportunity to firmly locate mental health within these horizontal health systems strengthening funding agendas. Although this approach will promote systems more enabling of scaling-up of mental health services, implications for donor funders and researchers alike is the need for increased time commitments, resources and investment in local control.


Subject(s)
Delivery of Health Care, Integrated/organization & administration , Health Policy , Mental Disorders/therapy , Mental Health Services/statistics & numerical data , Developing Countries , Evidence-Based Practice , Global Health , Health Priorities , Health Services Research , Humans , Mental Health , Mental Health Services/organization & administration , Quality of Health Care , South Africa
5.
Epidemiol Psychiatr Sci ; 29: e101, 2020 Feb 07.
Article in English | MEDLINE | ID: mdl-32029018

ABSTRACT

Against the backdrop of mounting calls for the global scaling-up of mental health services - including quality care and prevention services - there is very little guidance internationally on strategies for scaling-up such services. Drawing on lessons from scale-up attempts in six low- and middle-income countries (LMICs), and using exemplars from the front-lines in South Africa; we illustrate how health reforms towards people-centred chronic disease management provide enabling policy window opportunities for embedding mental health scale-up strategies into these reforms. Rather than going down the oft-trodden road of vertical funding for scale-up of mental health services, we suggest using the policy window that stresses global policy shifts towards strengthening of comprehensive integrated primary health care systems that are responsive to multimorbid chronic conditions. This is indeed a substantial opportunity to firmly locate mental health within these horizontal health systems strengthening funding agendas. While this approach will promote systems more enabling of scaling up of mental health services, implications for donor funders and researchers alike is the need for increased time commitments, resources and investment in local control.


Subject(s)
Global Health , Health Policy , Mental Health Services/organization & administration , Mental Health , Delivery of Health Care, Integrated , Developing Countries , Humans , Quality of Health Care , South Africa
6.
Epidemiol Psychiatr Sci ; 28(2): 199-209, 2019 Apr.
Article in English | MEDLINE | ID: mdl-28805174

ABSTRACT

AIMS: There is convincing evidence that lower socioeconomic position is associated with increased risk of mental disorders. However, the mechanisms involved are not well understood. This study aims to elucidate the causal pathways between socioeconomic position and depression symptoms in South African adults. Two possible causal theories are examined: social causation, which suggests that poor socioeconomic conditions cause mental ill health; and social drift, which suggests that those with poor mental health are more likely to drift into poor socioeconomic circumstances. METHODS: The study used longitudinal and cross-sectional observational data on 3904 adults, from a randomised trial carried out in 38 primary health care clinics between 2011 and 2012. Structural equation models and counterfactual mediation analyses were used to examine causal pathways in two directions. First, we examined social causation pathways, with language (a proxy for racial or ethnic category) being treated as an exposure, while education, unemployment, income and depression were treated as sequential mediators and outcomes. Second, social drift was explored with depression treated as a potential influence on health-related quality of life, job loss and, finally, income. RESULTS: The results suggest that the effects of language on depression at baseline, and on changes in depression during follow-up, were mediated through education and income but not through unemployment. Adverse effects of unemployment and job loss on depression appeared to be mostly mediated through income. The effect of depression on decreasing income appeared to be mediated by job loss. CONCLUSIONS: These results suggest that both social causation and social selection processes operate concurrently. This raises the possibility that people could get trapped in a vicious cycle in which poor socioeconomic conditions lead to depression, which, in turn, can cause further damage to their economic prospects. This study also suggests that modifiable factors such as income, employment and treatable depression are suitable targets for intervention in the short to medium term, while in the longer term reducing inequalities in education will be necessary to address the deeply entrenched inequalities in South Africa.


Subject(s)
Chronic Disease/psychology , Cost of Illness , Depression/epidemiology , Employment/statistics & numerical data , Income/statistics & numerical data , Quality of Life/psychology , Socioeconomic Factors , Unemployment/psychology , Adult , Chronic Disease/epidemiology , Comorbidity , Cross-Sectional Studies , Depression/psychology , Female , Humans , Longitudinal Studies , South Africa/epidemiology , Unemployment/statistics & numerical data , Young Adult
7.
Biomol NMR Assign ; 12(1): 47-50, 2018 04.
Article in English | MEDLINE | ID: mdl-28929458

ABSTRACT

BCL6 is a transcriptional repressor. Two domains of the protein, the N-terminal BTB-POZ domain and the RD2 domain are responsible for recruitment of co-repressor molecules and histone deacetylases. The BTB-POZ domain is found in a large and diverse range of proteins that play important roles in development, homeostasis and neoplasia. Crystal structures of several BTB-POZ domains, including BCL6 have been determined. The BTB-POZ domain of BCL6 not only mediates dimerisation but is also responsible for recruitment of co-repressors such as SMRT, NCOR and BCOR. Interestingly both SMRT and BCOR bind to the same site within the BCL6 BTB-POZ domain despite having very different primary sequences. Since both peptides and small molecules have been shown to bind to the co-repressor binding site it would suggest that the BTB_POZ domain is a suitable target for drug discovery. Here we report near complete backbone 15N, 13C and 1H assignments for the BTB-POZ domain of BCL6 to assist in the analysis of binding modes for small molecules.


Subject(s)
BTB-POZ Domain , Nuclear Magnetic Resonance, Biomolecular , Proto-Oncogene Proteins c-bcl-6/chemistry , Amino Acid Sequence , Humans
9.
S Afr Med J ; 106(12): 1241-1246, 2016 Dec 01.
Article in English | MEDLINE | ID: mdl-27917771

ABSTRACT

BACKGROUND: Low socioeconomic status is associated with the risk of hypertension. There are few reports of the effect of socioeconomic and potentially modifiable factors on the control of hypertension in South Africa (SA). OBJECTIVES: To investigate associations between patients' socio-economic status and characteristics of primary healthcare facilities, and control and treatment of blood pressure in hypertensive patients. METHODS: We enrolled hypertensive patients attending 38 public sector primary care clinics in the Western Cape, SA, in 2011, and followed them up 14 months later as part of a randomised controlled trial. Blood pressure was measured and prescriptions for antihypertension medications were recorded at baseline and follow-up. Logistic regression models assessed associations between patients' socioeconomic status, characteristics of primary healthcare facilities, and control and treatment of blood pressure. RESULTS: Blood pressure was uncontrolled in 60% (1 917/3 220) of patients at baseline, which was less likely in patients with a higher level of education (p=0.001) and in English compared with Afrikaans respondents (p=0.033). Treatment was intensified in 48% (892/1 872) of patients with uncontrolled blood pressure at baseline, which was more likely in patients with higher blood pressure at baseline (p<0.001), concurrent diabetes (p=0.013), more education (p=0.020), and those who attended clinics offering off-site drug supply (p=0.009), with a doctor every day (p=0.004), or with more nurses (p<0.001). CONCLUSION: Patient and clinic factors influence blood pressure control and treatment in primary care clinics in SA. Potential modifiable factors include ensuring effective communication of health messages, providing convenient access to medications, and addressing staff shortages in primary care clinics.

10.
Cell Death Differ ; 19(9): 1424-34, 2012 Sep.
Article in English | MEDLINE | ID: mdl-22361683

ABSTRACT

Ubiquitin (Ub)-mediated proteasome-dependent proteolysis is critical in regulating multiple biological processes including apoptosis. We show that the unstructured BH3-only protein, NOXA, is degraded by an Ub-independent mechanism requiring 19S regulatory particle (RP) subunits of the 26S proteasome, highlighting the possibility that other unstructured proteins reported to be degraded by 20S proteasomes in vitro may be bona fide 26S proteasome substrates in vivo. A lysine-less NOXA (NOXA-LL) mutant, which is not ubiquitinated, is degraded at a similar rate to wild-type NOXA. Myeloid cell leukemia 1, but not other anti-apoptotic BCL-2 family proteins, stabilizes NOXA by interaction with the NOXA BH3 domain. Depletion of 19S RP subunits, but not alternate proteasome activator REG subunits, increases NOXA half-life in vivo. A NOXA-LL mutant, which is not ubiquitinated, also requires an intact 26S proteasome for degradation. Depletion of the 19S non-ATPase subunit, PSMD1 induces NOXA-dependent apoptosis. Thus, disruption of 26S proteasome function by various mechanisms triggers the rapid accumulation of NOXA and subsequent cell death strongly implicating NOXA as a sensor of 26S proteasome integrity.


Subject(s)
Proteasome Endopeptidase Complex/metabolism , Proteolysis , Proto-Oncogene Proteins c-bcl-2/metabolism , Ubiquitin/metabolism , Apoptosis/physiology , HeLa Cells , Humans , Mutation, Missense , Myeloid Cell Leukemia Sequence 1 Protein , Proteasome Endopeptidase Complex/genetics , Proto-Oncogene Proteins c-bcl-2/genetics , Ubiquitin/genetics , Ubiquitination/physiology
11.
Int J Tuberc Lung Dis ; 14(3): 311-7, 2010 Mar.
Article in English | MEDLINE | ID: mdl-20132622

ABSTRACT

SETTING: Public sector primary care clinics in Free State Province, South Africa. OBJECTIVES: To investigate the effects of on-site in-service clinical skills training for nurse practitioners on tuberculosis (TB) treatment outcomes in the same clinics. DESIGN: Analysis of TB programme data from clinics taking part in two consecutive randomised trials of educational outreach aimed at improving respiratory and human immunodeficiency virus/acquired immune-deficiency syndrome care based on the Practical Approach to Lung Health. We compared treatment outcomes between control and intervention clinics among all patients diagnosed with TB during either trial. RESULTS: During the two trials, participating clinics treated 4187 and 2333 TB patients, respectively. Neither intervention was associated with better outcomes overall. However, among retreatment patients, cure or completion rates in intervention clinics were significantly higher during the second trial (OR 1.78, 95%CI 1.13-2.76). Patients in clinics that had received both interventions had higher cure or completion rates (OR 1.99, 95%CI 1.53-2.58) and lower default rates (OR 0.25, 95%CI 0.097-0.63) than patients in clinics that had received neither intervention. CONCLUSION: Although not primarily focused on TB treatment, the interventions appeared to improve successful treatment completion rates among TB retreatment cases. Integrated care programmes support attainment of important TB programme goals.


Subject(s)
Antitubercular Agents/therapeutic use , Nurse Practitioners/education , Tuberculosis/drug therapy , Adult , Clinical Competence , Female , Humans , Inservice Training/methods , Male , Middle Aged , Primary Health Care/methods , Public Sector , Randomized Controlled Trials as Topic , Retreatment , Retrospective Studies , South Africa/epidemiology , Treatment Outcome
12.
BMC Health Serv Res ; 8: 240, 2008 Nov 18.
Article in English | MEDLINE | ID: mdl-19017394

ABSTRACT

BACKGROUND: South Africa recently launched a national antiretroviral treatment programme. This has created an urgent need for nurse-training in antiretroviral treatment (ART) delivery. The PALSA PLUS programme provides guidelines and training for primary health care (PHC) nurses in the management of adult lung diseases and HIV/AIDS, including ART. A process evaluation was undertaken to document the training, explore perceptions regarding the value of the training, and compare the PALSA PLUS training approach (used at intervention sites) with the provincial training model. The evaluation was conducted alongside a randomized controlled trial measuring the effects of the PALSA PLUS nurse-training (Trial reference number ISRCTN24820584). METHODS: Qualitative methods were utilized, including participant observation of training sessions, focus group discussions and interviews. Data were analyzed thematically. RESULTS: Nurse uptake of PALSA PLUS training, with regard not only to ART specific components but also lung health, was high. The ongoing on-site training of all PHC nurses, as opposed to the once-off centralized training provided for ART nurses only at non-intervention clinics, enhanced nurses' experience of support for their work by allowing, not only for ongoing experiential learning, supervision and emotional support, but also for the ongoing managerial review of all those infrastructural and system-level changes required to facilitate health provider behaviour change and guideline implementation. The training of all PHC nurses in PALSA PLUS guideline use, as opposed to ART nurses only, was also perceived to better facilitate the integration of AIDS care within the clinic context. CONCLUSION: PALSA PLUS training successfully engaged all PHC nurses in a comprehensive approach to a range of illnesses affecting both HIV positive and negative patients. PHC nurse-training for integrated systems-based interventions should be prioritized on the ART funding agenda. Training for individual provider behaviour change is nonetheless only one aspect of the ongoing system-wide interventions required to effect lasting improvements in patient care in the context of an over-burdened and under-resourced PHC system.


Subject(s)
Anti-Retroviral Agents/therapeutic use , Education, Nursing, Continuing/methods , HIV Infections/drug therapy , Patient Care Planning , Public Health Nursing/education , Community Health Centers , Delivery of Health Care , Focus Groups , Humans , Practice Guidelines as Topic , Problem-Based Learning , Randomized Controlled Trials as Topic , South Africa
13.
Allergy ; 62(3): 224-9, 2007 Mar.
Article in English | MEDLINE | ID: mdl-17298338

ABSTRACT

BACKGROUND: Efforts to improve the care of patients with asthma and allergic conditions is in some developing countries being overwhelmed by the burden of tuberculosis, HIV/AIDS and other infectious diseases. Innovative approaches are required to ensure that these diseases are not neglected. METHODS: The Practical Approach to Lung Health in South Africa is an example of a syndromic integrated algorithm-based diagnostic and management tool for priority chronic respiratory diseases and tuberculosis. It was developed for the needs of nurse care practitioners in poorly-resourced and predominantly rural clinics and includes allergic diseases and asthma. Its diagnostic accuracy and effectiveness at improving the care offered to patients with asthma and rhinitis has been confirmed in two large studies performed in primary care clinics. DISCUSSION AND CONCLUSION: An integrated approach to the management of allergic diseases alongside other priority lung diseases may hold the key to ensuring that the needs of patients with these diseases gain and maintain recognition, and that health resources are appropriately allocated in developing countries.


Subject(s)
Developing Countries , Hypersensitivity/diagnosis , Hypersensitivity/therapy , Practice Guidelines as Topic , Primary Health Care/organization & administration , Algorithms , Chronic Disease/drug therapy , Health Services Needs and Demand/organization & administration , Humans , South Africa , Tuberculosis, Pulmonary/diagnosis
14.
Int Nurs Rev ; 53(4): 261-8, 2006 Dec.
Article in English | MEDLINE | ID: mdl-17083414

ABSTRACT

AIM: This paper describes the design, facilitation and preliminary assessment of a 1-week cascade training programme for nurse trainers in preparation for implementation of the Practical Approach to Lung Health in South Africa (PALSA) intervention, tested within the context of a pragmatic cluster randomized controlled trial in the Free State province. PALSA combines evidence-based syndromic guidelines on the management of respiratory disease in adults with group educational outreach to nurse practitioners. BACKGROUND: Evidence-based strategies to facilitate the implementation of primary care guidelines in low- to middle-income countries are limited. In South Africa, where the burden of respiratory diseases is high and growing, documentation and evaluation of training programmes in chronic conditions for health professionals is limited. METHOD: The PALSA training design aimed for coherence between the content of the guidelines and the facilitation process that underpins adult learning. Content facilitation involved the use of key management principles (key messages) highlighted in nurse-centred guidelines manual and supplemented by illustrated material and reminders. Process facilitation entailed reflective and experiential learning, role-playing and non-judgemental feedback. DISCUSSION AND RESULTS: Preliminary feedback showed an increase in trainers' self-awareness and self-confidence. Process and content facilitators agreed that the integrated training approach was balanced. All participants found that the training was motivational, minimally prescriptive, highly nurse-centred and offered personal growth. CONCLUSION: In addition to tailored guideline recommendations, training programmes should consider individual learning styles and adult learning processes.


Subject(s)
Education, Nursing, Continuing/methods , Education, Nursing, Continuing/organization & administration , Guideline Adherence , Lung Diseases/nursing , Practice Guidelines as Topic , Respiratory Tract Infections/nursing , Humans , South Africa
15.
Respir Res ; 7: 13, 2006 Jan 24.
Article in English | MEDLINE | ID: mdl-16433920

ABSTRACT

BACKGROUND: To compare the efficacy and safety of budesonide/formoterol (Symbicort) with formoterol (Oxis) in the treatment of patients with acute asthma who showed evidence of refractoriness to short-acting beta2-agonist therapy. METHODS: In a 3 hour, randomized, double-blind study, a total of 115 patients with acute asthma (mean FEV1 40% of predicted normal) and a refractory response to salbutamol (mean reversibility 2% of predicted normal after inhalation of 400 microg), were randomized to receive either budesonide/formoterol (320/9 microg, 2 inhalations at t = -5 minutes and 2 inhalations at 0 minutes [total dose 1280/36 microg]) or formoterol (9 microg, 2 inhalations at t = -5 minutes and 2 inhalations at 0 minutes [total dose 36 microg]). The primary efficacy variable was the average FEV1 from the first intake of study medication to the measurement at 90 minutes. Secondary endpoints included changes in FEV1 at other timepoints and change in respiratory rate at 180 minutes. Treatment success, treatment failure and patient assessment of the effectiveness of the study medication were also measured. RESULTS: FEV1 increased after administration of the study medication in both treatment groups. No statistically significant difference between the treatment groups was apparent for the primary outcome variable, or for any of the other efficacy endpoints. There were no statistically significant between-group differences for treatment success, treatment failure or patient assessment of medication effectiveness. Both treatments were well tolerated. CONCLUSION: Budesonide/formoterol and formoterol provided similarly rapid relief of acute bronchoconstriction in patients with asthma who showed evidence of refractoriness to a short-acting beta2-agonist.


Subject(s)
Adrenergic beta-Agonists/therapeutic use , Albuterol/therapeutic use , Asthma/drug therapy , Asthma/physiopathology , Bronchodilator Agents/therapeutic use , Budesonide/therapeutic use , Ethanolamines/therapeutic use , Acute Disease , Bronchodilator Agents/adverse effects , Budesonide/adverse effects , Double-Blind Method , Drug Combinations , Drug Resistance , Ethanolamines/adverse effects , Forced Expiratory Volume , Formoterol Fumarate , Humans , Lung/physiopathology , Respiratory Function Tests , Time Factors , Treatment Outcome
16.
Mol Cell ; 8(2): 351-61, 2001 Aug.
Article in English | MEDLINE | ID: mdl-11545737

ABSTRACT

TRF1 and TRF2 are key components of vertebrate telomeres. They bind to double-stranded telomeric DNA as homodimers. Dimerization involves the TRF homology (TRFH) domain, which also mediates interactions with other telomeric proteins. The crystal structures of the dimerization domains from human TRF1 and TRF2 were determined at 2.9 and 2.2 A resolution, respectively. Despite a modest sequence identity, the two TRFH domains have the same entirely alpha-helical architecture, resembling a twisted horseshoe. The dimerization interfaces feature unique interactions that prevent heterodimerization. Mutational analysis of TRF1 corroborates the structural data and underscores the importance of the TRFH domain in dimerization, DNA binding, and telomere localization. A possible structural homology between the TRFH domain of fission yeast telomeric protein Taz1 with those of the vertebrate TRFs is suggested.


Subject(s)
DNA-Binding Proteins/chemistry , Protein Structure, Tertiary , Schizosaccharomyces pombe Proteins , Telomere-Binding Proteins , Amino Acid Sequence , Crystallography, X-Ray , DNA-Binding Proteins/genetics , Dimerization , Fungal Proteins/genetics , Humans , Models, Molecular , Molecular Sequence Data , Mutagenesis, Site-Directed , Nuclear Proteins/chemistry , Protein Binding , RNA-Binding Proteins/chemistry , Sequence Alignment , Telomere/chemistry , Telomeric Repeat Binding Protein 1 , Telomeric Repeat Binding Protein 2
17.
EMBO J ; 18(20): 5735-44, 1999 Oct 15.
Article in English | MEDLINE | ID: mdl-10523316

ABSTRACT

TRF1 is a key player in telomere length regulation. Because length control was proposed to depend on the architecture of telomeres, we studied how TRF1 binds telomeric TTAGGG repeat DNA and alters its conformation. Although the single Myb-type helix-turn-helix motif of a TRF1 monomer can interact with telomeric DNA, TRF1 predominantly binds as a homodimer. Systematic Evolution of Ligands by Exponential enrichment (SELEX) with dimeric TRF1 revealed a bipartite telomeric recognition site with extreme spatial variability. Optimal sites have two copies of a 5'-YTAGGGTTR-3' half-site positioned without constraint on distance or orientation. Analysis of binding affinities and DNase I footprinting showed that both half-sites are simultaneously contacted by the TRF1 dimer, and electron microscopy revealed looping of the intervening DNA. We propose that a flexible segment in TRF1 allows the two Myb domains of the homodimer to interact independently with variably positioned half-sites. This unusual DNA binding mode is directly relevant to the proposed architectural role of TRF1.


Subject(s)
DNA-Binding Proteins/metabolism , Telomere/metabolism , Base Sequence , Binding Sites , DNA/genetics , DNA/metabolism , DNA/ultrastructure , DNA Primers/genetics , DNA-Binding Proteins/chemistry , Dimerization , Humans , In Vitro Techniques , Ligands , Microscopy, Electron , Models, Molecular , Molecular Sequence Data , Polymerase Chain Reaction/methods , Protein Structure, Quaternary , Proto-Oncogene Proteins c-myb/chemistry , Proto-Oncogene Proteins c-myb/metabolism , Telomeric Repeat Binding Protein 1
18.
Nucleic Acids Res ; 26(7): 1731-40, 1998 Apr 01.
Article in English | MEDLINE | ID: mdl-9512546

ABSTRACT

Telomeres consist of tandem arrays of short G-rich sequence motifs packaged by specific DNA binding proteins. In humans the double-stranded telomeric TTAGGG repeats are specifically bound by TRF1 and TRF2. Although telomere binding proteins from evolutionarily distant species are not sequence homologues, they share a Myb-like DNA binding motif. Here we have used gel retardation, primer extension and DNase I footprinting analyses to define the binding site of the isolated Myb-like domain of TRF1 and present a three-dimensional model for its interaction with human telomeric DNA. Our results suggest that the Myb-like domain of TRF1 recognizes a binding site centred on the sequence GGGTTA and that its DNA binding mode is similar to that of the homeodomain-like motifs of the yeast telomere binding protein RAP1. The implications of these findings for recognition of telomeric DNA in general are discussed.


Subject(s)
DNA-Binding Proteins/chemistry , DNA-Binding Proteins/metabolism , DNA/chemistry , DNA/metabolism , Telomere/metabolism , Amino Acid Sequence , Base Sequence , Binding Sites , DNA Footprinting , Deoxyribonuclease I , Humans , Models, Molecular , Molecular Sequence Data , Nuclear Proteins/chemistry , Nuclear Proteins/metabolism , Nucleic Acid Conformation , Oligodeoxyribonucleotides/chemistry , Oligodeoxyribonucleotides/metabolism , Protein Conformation , Proto-Oncogene Proteins/chemistry , Proto-Oncogene Proteins c-myb , Repetitive Sequences, Nucleic Acid , Sequence Alignment , Sequence Homology, Amino Acid , Telomeric Repeat Binding Protein 1 , Trans-Activators/chemistry
19.
Philos Trans R Soc Lond B Biol Sci ; 351(1339): 501-9, 1996 Apr 29.
Article in English | MEDLINE | ID: mdl-8735272

ABSTRACT

Understanding how proteins recognize DNA in a sequence-specific manner is central to our understanding of the regulation of transcription and other cellular processes. In this article we review the principles of DNA recognition that have emerged from the large number of high-resolution crystal structures determined over the last 10 years. The DNA-binding domains of transcription factors exhibit surprisingly diverse protein architectures, yet all achieve a precise complementarity of shape facilitating specific chemical recognition of their particular DNA targets. Although general rules for recognition can be derived, the complex nature of the recognition mechanism precludes a simple recognition code. In particular, it has become evident that the structure and flexibility of DNA and contacts mediated by water molecules contribute to the recognition process. Nevertheless, based on known structures it has proven possible to design proteins with novel recognition specificities. Despite this considerable practical success, the thermodynamic and kinetic properties of protein/DNA recognition remain poorly understood.


Subject(s)
DNA-Binding Proteins/chemistry , DNA-Binding Proteins/metabolism , DNA/chemistry , DNA/metabolism , Transcription Factors/chemistry , Transcription Factors/metabolism , Amino Acid Sequence , Base Composition , Base Sequence , Binding Sites , Consensus Sequence , Models, Molecular , Nucleic Acid Conformation , Protein Conformation , Protein Structure, Secondary , TATA Box , TATA-Box Binding Protein , Thermodynamics , Zinc Fingers
20.
Nature ; 366(6454): 483-7, 1993 Dec 02.
Article in English | MEDLINE | ID: mdl-8247159

ABSTRACT

The Cys2-His2 zinc-finger is the most widely occurring DNA-binding motif. The first structure of a zinc-finger/DNA complex revealed a fairly simple mechanism for DNA recognition suggesting that the zinc-finger might represent a candidate template for designing proteins to recognize DNA. Residues at three key positions in an alpha-helical 'reading head' play a dominant role in base-recognition and have been targets for mutagenesis experiments aimed at deriving a recognition code. Here we report the structure of a two zinc-finger DNA-binding domain from the protein Tramtrack complexed with DNA. The amino-terminal zinc-finger and its interaction with DNA illustrate several novel features. These include the use of a serine residue, which is semi-conserved and located outside the three key positions, to make a base contact. Its role in base-recognition correlates with a large, local, protein-induced deformation of the DNA helix at a flexible A-T-A sequence and may give insight into previous mutagenesis experiments. It is apparent from this structure that zinc-finger/DNA recognition is more complex than was originally perceived.


Subject(s)
DNA-Binding Proteins/chemistry , DNA/metabolism , Drosophila Proteins , Repressor Proteins , Transcription Factors/chemistry , Zinc Fingers , Amino Acid Sequence , Base Sequence , Crystallization , Crystallography, X-Ray , DNA-Binding Proteins/metabolism , Models, Molecular , Molecular Sequence Data , Protein Structure, Secondary , Transcription Factors/metabolism
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