@article{SiegelVasquezHonetal.2014,
  author    = {Siegel, T. Nicolai and Vasquez, Juan-Jos{\´e} and Hon, Chung-Chau and Vanselow, Jens T. and Schlosser, Andreas},
  title     = {Comparative ribosome profiling reveals extensive translational complexity in different Trypanosoma brucei life cycle stages},
  doi       = {10.1093/nar/gkt1386},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-112657},
  year      = {2014},
  abstract  = {While gene expression is a fundamental and tightly controlled cellular process that is regulated at multiple steps, the exact contribution of each step remains unknown in any organism. The absence of transcription initiation regulation for RNA polymerase II in the protozoan parasite Trypanosoma brucei greatly simplifies the task of elucidating the contribution of translation to global gene expression. Therefore, we have sequenced ribosome-protected mRNA fragments in T. brucei, permitting the genome-wide analysis of RNA translation and translational efficiency. We find that the latter varies greatly between life cycle stages of the parasite and ∼100-fold between genes, thus contributing to gene expression to a similar extent as RNA stability. The ability to map ribosome positions at sub-codon resolution revealed extensive translation from upstream open reading frames located within 5' UTRs and enabled the identification of hundreds of previously un-annotated putative coding sequences (CDSs). Evaluation of existing proteomics and genome-wide RNAi data confirmed the translation of previously un-annotated CDSs and suggested an important role for >200 of those CDSs in parasite survival, especially in the form that is infective to mammals. Overall our data show that translational control plays a prevalent and important role in different parasite life cycle stages of T. brucei.},
  subject      = {Ribosom},
  language  = {en}
}
@article{BatramJonesJanzenetal.2014,
  author    = {Batram, Christopher and Jones, Nivola G. and Janzen, Christian J. and Markert, Sebastian M. and Engstler, Markus},
  title     = {Expression site attenuation mechanistically links antigenic variation and development in Trypanosoma brucei},
  series = {eLife},
  volume    = {3},
  journal   = {eLife},
  number    = {e02324},
  issn      = {2050-084X},
  doi       = {10.7554/eLife.02324},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-119727},
  year      = {2014},
  abstract  = {We have discovered a new mechanism of monoallelic gene expression that links antigenic variation, cell cycle, and development in the model parasite Trypanosoma brucei. African trypanosomes possess hundreds of variant surface glycoprotein (VSG) genes, but only one is expressed from a telomeric expression site (ES) at any given time. We found that the expression of a second VSG alone is sufficient to silence the active VSG gene and directionally attenuate the ES by disruptor of telomeric silencing-1B (DOT1B)-mediated histone methylation. Three conserved expression-site-associated genes (ESAGs) appear to serve as signal for ES attenuation. Their depletion causes G1-phase dormancy and reversible initiation of the slender-to-stumpy differentiation pathway. ES-attenuated slender bloodstream trypanosomes gain full developmental competence for transformation to the tsetse fly stage. This surprising connection between antigenic variation and developmental progression provides an unexpected point of attack against the deadly sleeping sickness.},
  language  = {en}
}
@phdthesis{Dindar2014,
  author    = {Dindar, G{\"u}lcin},
  title     = {Molecular basis for product-specificity of DOT1 methyltransferases in Trypanosoma brucei},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-102524},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2014},
  abstract  = {Post-translational histone modifications (PTMs) such as methylation of lysine residues influence chromatin structure and function. PTMs are involved in different cellular processes such as DNA replication, transcription and cell differentiation. Deregulations of PTM patterns are responsible for a variety of human diseases including acute leukemia. DOT1 enzymes are highly conserved histone methyltransferases that are responsible for methylation of lysine 79 on histone H3 (H3K79). Most eukaryotes contain one single DOT1 enzyme, whereas African trypanosomes have two homologues, DOT1A and DOT1B, which methylate H3K76 (H3K76 is homologous to H3K79 in other organisms). DOT1A is essential and mediates mono- and di-methylations, whereas DOT1B additionally catalyzes tri-methylation of H3K76. However, a mechanistic understanding how these different enzymatic activities are achieved is lacking. This thesis exploits the fact that trypanosomes possess two DOT1 enzymes with different catalytic properties to understand the molecular basis for the differential product-specificity of DOT1 enzymes. A trypanosomal nucleosome reconstitution system was established to analyze methyltransferase activity under defined in vitro conditions. Homology modeling allowed the identification of critical residues within and outside the catalytic center that modulate product-specificity. Exchange of these residues transferred the product-specificity from one enzyme to the other and revealed regulatory domains adjacent to the catalytic center. This work provides the first evidence that few specific residues in DOT1 enzymes are crucial to catalyze methyl-state-specific reactions. These results have also consequences for the functional understanding of homologous enzymes in other eukaryotes.},
  subject      = {Histon-Methyltransferase},
  language  = {en}
}