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DNA methylation patterns in the parasite Trypanosoma cruzi
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology. (Lena Åslund)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology. (Lena Åslund)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
(English)Manuscript (Other academic)
Abstract [en]

Although DNA methylation is found to be a major epigenetic regulator of vital cellular processes in most organisms, its role in the protozoan parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, remains largely unknown. In this study, we report detection of 5-methyl cytosine (m5C) in T. cruzi DNA and also determine the genomic distribution of m5C by methyl DNA immunoprecipitation (MeDIP). Some of the methylated genomic loci identified were within repetitive retrotransposons or pseudogenes, suggesting a probable role for DNA methylation in transcriptional silencing similar to what has been reported in various organisms. DNA methylation was also found at intergenic regions close to putative transcription start sites, as well as in regions of transcriptional termination, suggesting that these loci are characterized by a complex combination of activating (e.g. acH3, H3K4me3) and silencing (e.g. m5C) epigenetic modifications. Interestingly, both immunostaining and immunoprecipitation results clearly demonstrated that DNA methylation is especially abundant in kinetoplast minicircles DNA. Both global and locus-specific differences in DNA methylation were observed between non-replicative (i.e. trypomastigotes, stationary-phase epimastigotes) and replicative (i.e. logarithmic epimastigotes) stages of the parasite, suggesting a role for DNA methylation in T. cruzi development.

Keyword [en]
Trypanosoma cruzi; DNA methylation; minicircle
URN: urn:nbn:se:uu:diva-100262OAI: oai:DiVA.org:uu-100262DiVA: diva2:210557
Available from: 2009-04-02 Created: 2009-03-29 Last updated: 2010-02-22
In thesis
1. Gene Regulation and Epigenetic Mechanisms in the Parasite Trypanosoma cruzi
Open this publication in new window or tab >>Gene Regulation and Epigenetic Mechanisms in the Parasite Trypanosoma cruzi
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Trypanosomes are unicellular protozoan parasites responsible for several human diseases that affect millions of people and cause thousands of casualties every year. They also represent a primitive eukaryotic model system harboring unique processes and basic regulatory mechanisms such as RNA-editing, polycistronic transcription and trans-splicing, first described in these organisms. Unlike most eukaryotes where levels of gene expression are controlled at initiation of transcription, trypanosomes use post-transcriptional events as the main regulators. This thesis explores the epigenetic mechanisms involved in gene expression control in trypanosomes, providing the first evidences for a functional “histone-code” as well as the existence and location of DNA methylation in Trypanosoma cruzi.

Chromatin immunoprecipitation (ChIP) was used for the profiling of acetylated and methylated histones in T. cruzi, showing that the modified histones were exclusively localized at bidirectional transcription start sites. In addition, promoters from highly transcribed genes were found depleted of nucleosomes, while DNA regions expected to be silent were not enriched in the investigated modified histones. Furthermore, we showed that the histone patterns were developmentally regulated.

The first in depth characterization of the DNA methylation patterns in T. cruzi was presented in this work. We detected m5C in regions of transcriptional initiation and termination, retrotransposons, pseudogenes and the kinetoplast minicircle. We also showed that the amount of methylation changes during development, with an increase in non-replicative forms.

We also characterized the DNA-interacting properties of a T. cruzi polypyrimidine-tract binding protein (TcPTB), and its potential role as a transcription factor. TcPTB was found to interact with single-stranded DNA present in promoters bound by its mammalian homologue as well as to the region of transcriptional initiation in Leishmania major. We also demonstrated that T. cruzi polypyrimidine stretches were able to confer ssDNA conformations.

Overall, these results provide new insights into the biology of ancient pathogenic parasites, which might be exploited for drug development.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 55 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 446
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
urn:nbn:se:uu:diva-100265 (URN)978-91-554-7490-4 (ISBN)
Public defence
2009-05-14, Rudbeck Hall, Rudbeck Laboratory, Dag Hammarskjölds väg 20, Uppsala, 14:15 (English)
Available from: 2009-04-23 Created: 2009-03-29 Last updated: 2010-02-22Bibliographically approved

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