The nuclear proteome of Trypanosoma brucei

• Published in: PloS one Vol. 12; no. 7; p. e0181884
• Main Authors: Goos, Carina, Dejung, Mario, Janzen, Christian J, Butter, Falk, Kramer, Susanne
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 20-07-2017; Public Library of Science (PLoS)
• Subjects: African trypanosomiasis; Amino acid sequence; Antigens; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biology; Biology and Life Sciences; Blotting, Western; Butter; Cattle; Cell Nucleus - metabolism; Cell surface; Complement (Immunology); Developmental biology; DNA-directed RNA polymerase; Electrophoresis, Polyacrylamide Gel; Flies; Gene expression; Genetic aspects; Immune system; Localization; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Lysates; Mammals; Mass Spectrometry; Mass spectroscopy; Methods; Microscopy, Fluorescence; Midgut; Molecular biology; Organelles; Physiological aspects; Promoters; Proteins; Proteome; Proteomes; Protozoa; Protozoan Proteins - genetics; Protozoan Proteins - metabolism; Research and analysis methods; Ribonucleic acid; RNA; Scientific imaging; Splicing; Transcription; Trypanosoma brucei; Trypanosoma brucei brucei - cytology; Trypanosoma brucei brucei - metabolism; Trypanosome; Vector-borne diseases; Water analysis
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0181884

Trypanosoma brucei is a protozoan flagellate that is transmitted by tsetse flies into the mammalian bloodstream. The parasite has a huge impact on human health both directly by causing African sleeping sickness and indirectly, by infecting domestic cattle. The biology of trypanosomes involves some highly unusual, nuclear-localised processes. These include polycistronic transcription without classical promoters initiated from regions defined by histone variants, trans-splicing of all transcripts to the exon of a spliced leader RNA, transcription of some very abundant proteins by RNA polymerase I and antigenic variation, a switch in expression of the cell surface protein variants that allows the parasite to resist the immune system of its mammalian host. Here, we provide the nuclear proteome of procyclic Trypanosoma brucei, the stage that resides within the tsetse fly midgut. We have performed quantitative label-free mass spectrometry to score 764 significantly nuclear enriched proteins in comparison to whole cell lysates. A comparison with proteomes of several experimentally characterised nuclear and non-nuclear structures and pathways confirmed the high quality of the dataset: the proteome contains about 80% of all nuclear proteins and less than 2% false positives. Using motif enrichment, we found the amino acid sequence KRxR present in a large number of nuclear proteins. KRxR is a sub-motif of a classical eukaryotic monopartite nuclear localisation signal and could be responsible for nuclear localization of proteins in Kinetoplastida species. As a proof of principle, we have confirmed the nuclear localisation of six proteins with previously unknown localisation by expressing eYFP fusion proteins. While proteome data of several T. brucei organelles have been published, our nuclear proteome closes an important gap in knowledge to study trypanosome biology, in particular nuclear-related processes.