Publications by authors named "Paula Cardenas"

21 Publications

  • Page 1 of 1

Access barriers, self-recognition, and recognition of depression and unhealthy alcohol use: A qualitative study.

Rev Colomb Psiquiatr (Engl Ed) 2021 Jul 8;50 Suppl 1:52-63. Epub 2021 Aug 8.

Departmento de Psiquiatría, Geisel School of Medicine, Dartmouth College, Hanover, United States.

Introduction: Access to healthcare services involves a complex dynamic, where mental health conditions are especially disadvantaged, due to multiple factors related to the context and the involved stakeholders. However, a characterisation of this phenomenon has not been carried out in Colombia, and this motivates the present study.

Objectives: The objective of this study was to explore the causes that affect access to health services for depression and unhealthy alcohol use in Colombia, according to various stakeholders involved in the care process.

Methods: In-depth interviews and focus groups were conducted with health professionals, administrative professionals, users, and representatives of community health organisations in five primary and secondary-level institutions in three regions of Colombia. Subsequently, to describe access to healthcare for depression and unhealthy alcohol use, excerpts from the interviews and focus groups were coded through content analysis, expert consensus, and grounded theory. Five categories of analysis were created: education and knowledge of the health condition, stigma, lack of training of health professionals, culture, and structure or organisational factors.

Results: We characterised the barriers to a lack of illness recognition that affected access to care for depression or unhealthy alcohol use according to users, healthcare professionals and administrative staff from five primary and secondary care centres in Colombia. The groups identified that lack of recognition of depression was related to low education and knowledge about this condition within the population, stigma, and lack of training of health professionals, as well as to culture. For unhealthy alcohol use, the participants identified that low education and knowledge about this condition, lack of training of healthcare professionals, and culture affected its recognition, and therefore, healthcare access. Neither structural nor organisational factors seemed to play a role in the recognition or self-recognition of these conditions.

Conclusions: This study provides essential information for the search for factors that undermine access to mental health in the Colombian context. Likewise, it promotes the generation of hypotheses that can lead to the development and implementation of tools to improve care in the field of mental illness.
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http://dx.doi.org/10.1016/j.rcpeng.2021.06.008DOI Listing
July 2021

Barriers and facilitators to the diagnosis and treatment of depression in primary care in Colombia: Perspectives of providers, healthcare administrators, patients and community representatives.

Rev Colomb Psiquiatr (Engl Ed) 2021 Jul 17;50 Suppl 1:64-72. Epub 2021 Jul 17.

Center for Technology and Behavioral Health, Geisel School of Medicine, Dartmouth College, Lebanon, NH, USA.

Introduction: Depression represents a major disease burden in Colombia. To better understand opportunities to improve access to mental healthcare in Colombia, a research team at Javeriana University conducted formative qualitative research to explore stakeholders' experiences with the integration of mental healthcare into the primary care system.

Methods: The research team conducted 16 focus groups and 4 in-depth interviews with patients, providers, health administrators and representatives of community organisations at five primary care clinics in Colombia, and used thematic analysis to study the data.

Results: Themes were organised into barriers and facilitators at the level of patients, providers, organisations and facilities. Barriers to the treatment of depression included stigma, lack of mental health literacy at the patient and provider level, weak links between care levels, and continued need for mental health prioritization at the national level. Facilitators to the management of depression in primary care included patient support systems, strong patient-provider relationships, the targeting of depression interventions and national depression guidelines.

Discussion: This study elucidates the barriers to depression care in Colombia, and highlights action items for further integrating depression care into the primary care setting.
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http://dx.doi.org/10.1016/j.rcpeng.2021.01.001DOI Listing
July 2021

Addressing harmful alcohol use in primary care in Colombia: Understanding the sociocultural context.

Rev Colomb Psiquiatr (Engl Ed) 2021 Jul 16;50 Suppl 1:73-82. Epub 2021 Jul 16.

Center for Technology and Behavioral Health, Department of Psychiatry, Geisel School of Medicine at Dartmouth College.

Harmful alcohol use is a public health problem worldwide, contributing to an estimated 5.1% of the global burden of illness. Screening and addressing at-risk drinking in primary care settings is an empirically supported health care intervention strategy to help reduce the burden of alcohol-use problems. In preparation for introducing screening and treatment for at-risk drinking in primary care clinics in Colombia, we conducted interviews with clinicians, clinic administrators, patients, and participants in Alcoholics Anonymous. Interviews were conducted within the framework of the Detección y Atención Integral de Depresión y Abuso de Alcohol en Atención Primaria (DIADA, [Detection and Integrated Care for Depression and Alcohol Use in Primary Care] www.project-diada.org) research project, and its qualitative phase that consisted of the collection of data from 15 focus groups, 6 interviews and field observations in 5 regional settings. All participants provided informed consent to participate in this research. Findings revealed the association of harmful alcohol use with a culture of consumption, within which it is learned and socially accepted practice. Recognition of harmful alcohol consumption includes a social context that influences its screening, diagnosis and prevention. The discussion highlights how, despite the existence of institutional strategies in healthcare settings and the awareness of the importance of at-risk drinking among health personnel, the recognition of the harmful use of alcohol as a pathology should be embedded in an understanding of historical, social and cultural dimensions that may affect different identification and care scenarios.
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http://dx.doi.org/10.1016/j.rcpeng.2020.11.004DOI Listing
July 2021

or Knockdown in Mature, but Not Immature, T Lymphocytes Similarly Cripples the Human TCRαβ Complex.

Front Cell Dev Biol 2021 25;9:608490. Epub 2021 Jun 25.

Department of Immunology, Ophthalmology and ENT, Complutense University School of Medicine and 12 de Octubre Health Research Institute (imas12), Madrid, Spain.

The human αβ T-cell receptor (TCR) is composed of a variable heterodimer (TCRαβ) and three invariant dimers (CD3γε, CD3δε, and ζζ/CD247). The role of each invariant chain in the stepwise interactions among TCR chains along the assembly is still not fully understood. Despite the high sequence homology between CD3γ and CD3δ, the clinical consequences of the corresponding immunodeficiencies (ID) in humans are very different (mild and severe, respectively), and mouse models do not recapitulate findings in human ID. To try to understand such disparities, we stably knocked down (KD) or expression in the human Jurkat T-cell line and analyzed comparatively their impact on TCRαβ assembly, transport, and surface expression. The results indicated that TCR ensembles were less stable and CD3ε levels were lower when CD3γ, rather than CD3δ, was scarce. However, both defective TCR ensembles were strongly retained in the ER, lacked ζζ/CD247, and barely reached the T-cell surface (<11% of normal controls) in any of the KD cells. This is in sharp contrast to human CD3γ ID, whose mature T cells express higher levels of surface TCR (>30% vs. normal controls). KD of human T-cell progenitors followed by mouse fetal thymus organ cultures showed high plasticity in emerging immature polyclonal T lymphocytes that allowed for the expression of significant TCR levels which may then signal for survival in CD3γ, but not in CD3δ deficiency, and explain the immunological and clinical disparities of such ID cases.
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http://dx.doi.org/10.3389/fcell.2021.608490DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8268008PMC
June 2021

RarA Acts as a Positive RecA Accessory Protein.

Front Microbiol 2020 13;11:92. Epub 2020 Feb 13.

Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CSIC, Madrid, Spain.

Ubiquitous RarA AAA ATPases play crucial roles in the cellular response to blocked replication forks in pro- and eukaryotes. Here, we provide evidence that absence of RarA reduced the viability of Δ, Δ, and 15 cells during unperturbed growth. The gene was epistatic to and genes in response to HO- or MMS-induced DNA damage. Conversely, the inactivation of partially suppressed the HR defect of mutants lacking end-resection (Δ, Δ, Δ, Δ) or branch migration (Δ, Δ, Δ) activity. RarA contributes to RecA thread formation, that are thought to be the active forms of RecA during homology search. The absence of RarA reduced RecA accumulation, and the formation of visible RecA threads upon DNA damage. When Δ was combined with mutations in genuine RecA accessory genes, RecA accumulation was further reduced in Δ Δ and Δ Δ double mutant cells, and was blocked in Δ15 cells. These results suggest that RarA contributes to the assembly of RecA nucleoprotein filaments onto single-stranded DNA, and possibly antagonizes RecA filament disassembly.
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http://dx.doi.org/10.3389/fmicb.2020.00092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7031210PMC
February 2020

Perspectives, Experiences, and Practices in the Use of Digital Information Technologies in the Management of Depression and Alcohol Use Disorder in Health Care Systems in Colombia.

Qual Health Res 2020 05 13;30(6):906-916. Epub 2020 Feb 13.

Department of Epidemiology and Biostatistics, School of Medicine, Pontificia Universidad Javeriana, Bogota, Colombia.

Digital information technologies are increasingly used in the treatment of mental health disorders. Through this qualitative study, researchers illuminated perspectives, experiences, and practices among diverse stakeholders in the use of digital information technologies in the management of depression and alcohol use disorders in Colombia. In-depth interviews and focus groups were conducted in five primary care institutions across Colombia. Thematic analysis was used to analyze the data. The use of technology in the treatment of mental health disorders can facilitate the , and , as well as Potential barriers to the use of technology in this setting include challenges of , and This study can inform the implementation of digital information technologies in the care of depression and problematic alcohol use within health care systems in Colombia.
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http://dx.doi.org/10.1177/1049732320902460DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7265234PMC
May 2020

Lymphocyte integration of complement cues.

Semin Cell Dev Biol 2019 01 8;85:132-142. Epub 2018 Mar 8.

Department of Immunology, Ophthalmology and ENT, Complutense University School of Medicine and 12 de Octubre Health Research Institute (imas12), Madrid, Spain. Electronic address:

We address current data, views and puzzles on the emerging topic of regulation of lymphocytes by complement proteins or fragments. Such regulation is believed to take place through complement receptors (CR) and membrane complement regulators (CReg) involved in cell function or protection, respectively, including intracellular signalling. Original observations in B cells clearly support that complement cues through CR improve their performance. Other lymphocytes likely integrate complement-derived signals, as most lymphoid cells constitutively express or regulate CR and CReg upon activation. CR-induced signals, particularly by anaphylatoxins, clearly regulate lymphoid cell function. In contrast, data obtained by CReg crosslinking using antibodies are not always confirmed in human congenital deficiencies or knock-out mice, casting doubts on their physiological relevance. Unsurprisingly, human and mouse complement systems are not completely homologous, adding further complexity to our still fragmentary understanding of complement-lymphocyte interactions.
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http://dx.doi.org/10.1016/j.semcdb.2018.02.005DOI Listing
January 2019

Formative and Summative Assessment in Veterinary Pathology and Other Courses at a Mexican Veterinary College.

J Vet Med Educ Summer 2017;44(2):331-337. Epub 2016 Oct 25.

The Faculty of Veterinary Medicine and Animal Science of the National Autonomous University of Mexico (UNAM) uses the Moodle learning management system for formative and summative computer assessment. The authors of this article-the teacher primarily responsible for Moodle implementation and a researcher who is a recent Moodle adopter-describe and discuss the students' and teachers' attitudes to summative and formative computer assessment in Moodle. Item analysis of quiz results helped us to identify and fix poorly performing questions, which greatly reduced student complaints and improved objective assessment. The use of certainty-based marking (CBM) in formative assessment in veterinary pathology was well received by the students and should be extended to more courses. The importance of having proficient computer support personnel should not be underestimated. A properly translated language pack is essential for the use of Moodle in a language other than English.
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http://dx.doi.org/10.3138/jvme.1015-169RDOI Listing
August 2017

DNA double strand break end-processing and RecA induce RecN expression levels in Bacillus subtilis.

DNA Repair (Amst) 2014 Feb 25;14:1-8. Epub 2013 Dec 25.

Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, 28049 Madrid, Spain. Electronic address:

Bacillus subtilis cells respond to double strand breaks (DSBs) with an ordered recruitment of repair proteins to the site lesion, being RecN one of the first responders. In B. subtilis, one of the responses to DSBs is to increase RecN expression rather than modifying its turnover rate. End-processing activities and the RecA protein itself contribute to increase RecN levels after DNA DSBs. RecO is required for RecA filament formation and full SOS induction, but its absence did not significantly affect RecN expression. Neither the absence of LexA nor the phosphorylation state of RecA or SsbA significantly affect RecN expression levels. These findings identify two major mechanisms (SOS and DSB response) used to respond to DSBs, with LexA required for one of them (SOS response). The DSB response, which requires end-processing and RecA or short RecO-independent RecA filaments, highlights the importance of guarding genome stability by modulating the DNA damage responses.
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http://dx.doi.org/10.1016/j.dnarep.2013.12.001DOI Listing
February 2014

Early steps of double-strand break repair in Bacillus subtilis.

DNA Repair (Amst) 2013 Mar 4;12(3):162-76. Epub 2013 Feb 4.

Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma de Madrid, Darwin 3, Cantoblanco, 28049 Madrid, Spain.

All organisms rely on integrated networks to repair DNA double-strand breaks (DSBs) in order to preserve the integrity of the genetic information, to re-establish replication, and to ensure proper chromosomal segregation. Genetic, cytological, biochemical and structural approaches have been used to analyze how Bacillus subtilis senses DNA damage and responds to DSBs. RecN, which is among the first responders to DNA DSBs, promotes the ordered recruitment of repair proteins to the site of a lesion. Cells have evolved different mechanisms for efficient end processing to create a 3'-tailed duplex DNA, the substrate for RecA binding, in the repair of one- and two-ended DSBs. Strand continuity is re-established via homologous recombination (HR), utilizing an intact homologous DNA molecule as a template. In the absence of transient diploidy or of HR, however, two-ended DSBs can be directly re-ligated via error-prone non-homologous end-joining. Here we review recent findings that shed light on the early stages of DSB repair in Firmicutes.
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http://dx.doi.org/10.1016/j.dnarep.2012.12.005DOI Listing
March 2013

RecX facilitates homologous recombination by modulating RecA activities.

PLoS Genet 2012 20;8(12):e1003126. Epub 2012 Dec 20.

Department of Microbial Biotechnology, Centro Nacional de Biotechnología, Consejo Superior de Investigaciones Científicas, Madrid, Spain.

The Bacillus subtilis recH342 strain, which decreases interspecies recombination without significantly affecting the frequency of transformation with homogamic DNA, carried a point mutation in the putative recX (yfhG) gene, and the mutation was renamed as recX342. We show that RecX (264 residues long), which shares partial identity with the Proteobacterial RecX (<180 residues), is a genuine recombination protein, and its primary function is to modulate the SOS response and to facilitate RecA-mediated recombinational repair and genetic recombination. RecX-YFP formed discrete foci on the nucleoid, which were coincident in time with RecF, in response to DNA damage, and on the poles and/or the nucleoid upon stochastic induction of programmed natural competence. When DNA was damaged, the RecX foci co-localized with RecA threads that persisted for a longer time in the recX context. The absence of RecX severely impaired natural transformation both with plasmid and chromosomal DNA. We show that RecX suppresses the negative effect exerted by RecA during plasmid transformation, prevents RecA mis-sensing of single-stranded DNA tracts, and modulates DNA strand exchange. RecX, by modulating the "length or packing" of a RecA filament, facilitates the initiation of recombination and increases recombination across species.
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http://dx.doi.org/10.1371/journal.pgen.1003126DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3527212PMC
May 2013

Detection of the early stage of recombinational DNA repair by silicon nanowire transistors.

Nano Lett 2012 Mar 1;12(3):1275-81. Epub 2012 Mar 1.

Instituto de Microelectrónica de Madrid (IMM-CNM-CSIC), Isaac Newton 8, 28760 Tres Cantos, Madrid, Spain.

A silicon nanowire-based biosensor has been designed and applied for label-free and ultrasensitive detection of the early stage of recombinational DNA repair by RecA protein. Silicon nanowires transistors were fabricated by atomic force microscopy nanolithography and integrated into a microfluidic environment. The sensor operates by measuring the changes in the resistance of the nanowire as the biomolecular reactions proceed. We show that the nanoelectronic sensor can detect and differentiate several steps in the binding of RecA to a single-stranded DNA filament taking place on the nanowire-aqueous interface. We report relative changes in the resistance of 3.5% which are related to the interaction of 250 RecA·single-stranded DNA complexes. Spectroscopy data confirm the presence of the protein-DNA complexes on the functionalized silicon surfaces.
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http://dx.doi.org/10.1021/nl2037547DOI Listing
March 2012

Polynucleotide phosphorylase exonuclease and polymerase activities on single-stranded DNA ends are modulated by RecN, SsbA and RecA proteins.

Nucleic Acids Res 2011 Nov 22;39(21):9250-61. Epub 2011 Aug 22.

Centro Nacional de Biotecnología-CSIC, Darwin 3, 28049 Madrid, Spain.

Bacillus subtilis pnpA gene product, polynucleotide phosphorylase (PNPase), is involved in double-strand break (DSB) repair via homologous recombination (HR) or non-homologous end-joining (NHEJ). RecN is among the first responders to localize at the DNA DSBs, with PNPase facilitating the formation of a discrete RecN focus per nucleoid. PNPase, which co-purifies with RecA and RecN, was able to degrade single-stranded (ss) DNA with a 3' → 5' polarity in the presence of Mn(2+) and low inorganic phosphate (Pi) concentration, or to extend a 3'-OH end in the presence dNDP · Mn(2+). Both PNPase activities were observed in evolutionarily distant bacteria (B. subtilis and Escherichia coli), suggesting conserved functions. The activity of PNPase was directed toward ssDNA degradation or polymerization by manipulating the Pi/dNDPs concentrations or the availability of RecA or RecN. In its dATP-bound form, RecN stimulates PNPase-mediated polymerization. ssDNA phosphorolysis catalyzed by PNPase is stimulated by RecA, but inhibited by SsbA. Our findings suggest that (i) the PNPase degradative and polymerizing activities might play a critical role in the transition from DSB sensing to end resection via HR and (ii) by blunting a 3'-tailed duplex DNA, in the absence of HR, B. subtilis PNPase might also contribute to repair via NHEJ.
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http://dx.doi.org/10.1093/nar/gkr635DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3241651PMC
November 2011

Double-strand break repair in bacteria: a view from Bacillus subtilis.

FEMS Microbiol Rev 2011 Nov 18;35(6):1055-81. Epub 2011 May 18.

Departmento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Cantoblanco, Madrid, Spain.

In all living organisms, the response to double-strand breaks (DSBs) is critical for the maintenance of chromosome integrity. Homologous recombination (HR), which utilizes a homologous template to prime DNA synthesis and to restore genetic information lost at the DNA break site, is a complex multistep response. In Bacillus subtilis, this response can be subdivided into five general acts: (1) recognition of the break site(s) and formation of a repair center (RC), which enables cells to commit to HR; (2) end-processing of the broken end(s) by different avenues to generate a 3'-tailed duplex and RecN-mediated DSB 'coordination'; (3) loading of RecA onto single-strand DNA at the RecN-induced RC and concomitant DNA strand exchange; (4) branch migration and resolution, or dissolution, of the recombination intermediates, and replication restart, followed by (5) disassembly of the recombination apparatus formed at the dynamic RC and segregation of sister chromosomes. When HR is impaired or an intact homologous template is not available, error-prone nonhomologous end-joining directly rejoins the two broken ends by ligation. In this review, we examine the functions that are known to contribute to DNA DSB repair in B. subtilis, and compare their properties with those of other bacterial phyla.
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http://dx.doi.org/10.1111/j.1574-6976.2011.00272.xDOI Listing
November 2011

Overexpression of the recA gene decreases oral but not intraperitoneal fitness of Salmonella enterica.

Infect Immun 2010 Jul 10;78(7):3217-25. Epub 2010 May 10.

Departament de Genètica i Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra, Spain.

Transcription of the Salmonella enterica recA gene is negatively controlled by the LexA protein, the repressor of the SOS response. The introduction of a mutation (recAo6869) in the LexA binding site, in the promoter region of the S. enterica ATCC 14028 recA gene, allowed the analysis of the effect that RecA protein overproduction has on the fitness of this virulent strain. The fitness of orally but not intraperitoneally inoculated recAo6869 cells decreased dramatically. However, the SOS response of this mutant was induced normally, and there was no increase in the sensitivity of the strain toward DNA-damaging agents, bile salts, or alterations in pH. Nevertheless, S. enterica recAo6869 cells were unable to swarm and their capacity to cross the intestinal epithelium was significantly reduced. The swarming deficiency in recAo6869 cells is independent of the flagellar phase. Moreover, swimming activity of the recAo6869 strain was not diminished with respect to the wild type, indicating that the flagellar synthesis is not affected by RecA protein overproduction. In contrast, swarming was recovered in a recAo6869 derivative that overproduced CheW, a protein known to be essential for this function. These data demonstrate that an equilibrium between the intracellular concentrations of RecA and CheW is necessary for swarming in S. enterica. Our results are the first to point out that the SOS response plays a critical role in the prevention of DNA damage by abolishing bacterial swarming in the presence of a genotoxic compound.
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http://dx.doi.org/10.1128/IAI.01321-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2897385PMC
July 2010

Bacillus subtilis polynucleotide phosphorylase 3'-to-5' DNase activity is involved in DNA repair.

Nucleic Acids Res 2009 Jul 11;37(12):4157-69. Epub 2009 May 11.

Department of Microbial Biotechnology, Centro Nacional de Biotecnología, CSIC, C/Darwin 3, Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain.

In the presence of Mn(2+), an activity in a preparation of purified Bacillus subtilis RecN degrades single-stranded (ss) DNA with a 3' --> 5' polarity. This activity is not associated with RecN itself, because RecN purified from cells lacking polynucleotide phosphorylase (PNPase) does not show the exonuclease activity. We show here that, in the presence of Mn(2+) and low-level inorganic phosphate (P(i)), PNPase degrades ssDNA. The limited end-processing of DNA is regulated by ATP and is inactive in the presence of Mg(2+) or high-level P(i). In contrast, the RNase activity of PNPase requires Mg(2+) and P(i), suggesting that PNPase degradation of RNA and ssDNA occur by mutually exclusive mechanisms. A null pnpA mutation (DeltapnpA) is not epistatic with Delta recA, but is epistatic with DeltarecN and Delta ku, which by themselves are non-epistatic. The addA5, Delta recO, Delta recQ (Delta recJ), Delta recU and Delta recG mutations (representative of different epistatic groups), in the context of DeltapnpA, demonstrate gain- or loss-of-function by inactivation of repair-by-recombination, depending on acute or chronic exposure to the damaging agent and the nature of the DNA lesion. Our data suggest that PNPase is involved in various nucleic acid metabolic pathways, and its limited ssDNA exonuclease activity plays an important role in RecA-dependent and RecA-independent repair pathways.
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http://dx.doi.org/10.1093/nar/gkp314DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2709576PMC
July 2009

Dynamic structures of Bacillus subtilis RecN-DNA complexes.

Nucleic Acids Res 2008 Jan 13;36(1):110-20. Epub 2007 Nov 13.

Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma de Madrid, Darwin 3, Cantoblanco, 28049 Madrid, Spain.

Genetic and cytological evidences suggest that Bacillus subtilis RecN acts prior to and after end-processing of DNA double-strand ends via homologous recombination, appears to participate in the assembly of a DNA repair centre and interacts with incoming single-stranded (ss) DNA during natural transformation. We have determined the architecture of RecN-ssDNA complexes by atomic force microscopy (AFM). ATP induces changes in the architecture of the RecN-ssDNA complexes and stimulates inter-complex assembly, thereby increasing the local concentration of DNA ends. The large CII and CIII complexes formed are insensitive to SsbA (counterpart of Escherichia coli SSB or eukaryotic RPA protein) addition, but RecA induces dislodging of RecN from the overhangs of duplex DNA molecules. Reciprocally, in the presence of RecN, RecA does not form large RecA-DNA networks. Based on these results, we hypothesize that in the presence of ATP, RecN tethers the 3'-ssDNA ends, and facilitates the access of RecA to the high local concentration of DNA ends. Then, the resulting RecA nucleoprotein filaments, on different ssDNA segments, might promote the simultaneous genome-wide homology search.
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http://dx.doi.org/10.1093/nar/gkm759DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2248758PMC
January 2008

High level of conservation in Plasmodium vivax merozoite surface protein 4 (PvMSP4).

Infect Genet Evol 2005 Oct 18;5(4):354-61. Epub 2005 Jan 18.

Molecular Biology Department, Fundacion Instituto de Inmunologia de Colombia, Bogota, Colombia.

Plasmodium vivax merozoite surface protein 4 (PvMSP4) has been considered to be a promising malarial vaccine candidate. The antigenic diversity displayed by parasite populations is one of the main factors limiting the efficacy of asexual-stage anti-malarial vaccine candidates. The present study is the first characterising PvMSP4 polymorphism. P. vivax isolates were collected from endemic areas in Colombia and diversity and selection pattern studies were carried out. Overall conservation in this protein was remarkable. Changes were only found in exons I and II, the former only having single nucleotide polymorphisms (SNPs) whilst the latter showed variations in tandem repeat number caused by exon II slippage. The remaining regions (EGF-like domain, GPI anchor and intron) were completely conserved. Selection and neutrality tests carried out over variant exons indicated negative selective forces acting on them. No evidence of intragenic recombination was found. The strong conservation displayed in this molecule by isolates from geographically different regions (Colombia, Salvador and Thailand) stresses its potential importance as a candidate for a vaccine against P. vivax malaria.
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http://dx.doi.org/10.1016/j.meegid.2004.12.001DOI Listing
October 2005

The T-cell receptor in primates: identifying and sequencing new owl monkey TRBV gene sub-groups.

Immunogenetics 2005 Apr 12;57(1-2):42-52. Epub 2005 Feb 12.

Molecular Biology Department, Fundacion Instituto de Inmunologia de Colombia (FIDIC), Colombia, South America.

The New World primate Aotus nancymaae (owl monkey) has been shown to be an excellent experimental model when studying malarial parasites. Characterising the T-cell receptor (TR) alphabeta repertoire by means of the different variable beta (TRBV) genes displayed contributes to a better understanding of these lymphocytes' role in the response against several malarial antigens. This study describes identifying and characterising eleven new TRBV gene sub-groups in cDNA from Aotus nancymaae's peripheral blood lymphocytes; these 11 gene sequences displayed homology to the previously reported human TRBV3, TRBV10, TRBV11, TRBV14, TRBV18, TRBV19, TRBV20, TRBV25, TRBV27, TRBV29 and TRBV30 sub-groups, resulting in 83% overall homology at the amino acid level. An additional Aotus sequence was found having similarity with the human TRBJ-2-7*01 gene. Evolutionary relationships amongst these sequences and the homologous genes from both New and Old World primates have shown that the TRBV repertoire has been maintained in the species being studied, displaying varying association patterns and substitution rates, depending on the sub-group being studied. The degree of identity observed when comparing human and Aotus genes suggests that these species might have a similar TRBV repertoire.
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http://dx.doi.org/10.1007/s00251-004-0758-yDOI Listing
April 2005

MHC class I genes in the owl monkey: mosaic organisation, convergence and loci diversity.

Immunogenetics 2005 Feb 15;56(11):818-32. Epub 2005 Jan 15.

Molecular Biology Department, Fundacion Instituto de Inmunologia de Colombia, Bogota, Colombia.

The MHC class I molecule plays an important role in immune response, pathogen recognition and response against vaccines and self- versus non-self-recognition. Studying MHC class I characteristics thus became a priority when dealing with Aotus to ensure its use as an animal model for biomedical research. Isolation, cloning and sequencing of exons 1-8 from 27 MHC class I alleles obtained from 13 individuals classified as belonging to three owl monkey species (A. nancymaae, A. nigriceps and A. vociferans) were carried out to establish similarities between Aotus MHC class I genes and those expressed by other New and Old World primates. Six Aotus MHC class I sequence groups (Ao-g1, Ao-g2, Ao-g3, Ao-g4, Ao-g5 and Ao-g6) weakly related to non-classical Catarrhini MHC were identified. An allelic lineage was also identified in one A. nancymaae and two A. vociferans monkeys, exhibiting a high degree of conservation, negative selection along the molecule and premature termination of the open reading frame at exon 5 (Ao-g5). These sequences' high conservation suggests that they more likely correspond to a soluble form of Aotus MHC class I molecules than to a new group of processed pseudogenes. Another group, named Ao-g6, exhibited a strong relationship with Catarrhini's classical MHC-B-C loci. Sequence evolution and variability analysis indicated that Aotus MHC class I molecules experience inter-locus gene conversion phenomena, contributing towards their high variability.
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http://dx.doi.org/10.1007/s00251-004-0751-5DOI Listing
February 2005
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