title: Identification of the ISWI Chromatin Remodeling Complex of the Early Branching Eukaryote Trypanosoma brucei.
abstract: ISWI chromatin remodelers are highly conserved in eukaryotes and are important for the assembly and spacing of nucleosomes, thereby controlling transcription initiation and elongation. ISWI is typically associated with different subunits, forming specialized complexes with discrete functions. In the unicellular parasite Trypanosoma brucei, which causes African sleeping sickness, TbISWI down-regulates RNA polymerase I (Pol I)-transcribed variant surface glycoprotein (VSG) gene expression sites (ESs), which are monoallelically expressed. Here, we use tandem affinity purification to determine the interacting partners of TbISWI. We identify three proteins that do not show significant homology with known ISWI-associated partners. Surprisingly, one of these is nucleoplasmin-like protein (NLP), which we had previously shown to play a role in ES control. In addition, we identify two novel ISWI partners, regulator of chromosome condensation 1-like protein (RCCP) and phenylalanine/tyrosine-rich protein (FYRP), both containing protein motifs typically found on chromatin proteins. Knockdown of RCCP or FYRP in bloodstream form T. brucei results in derepression of silent variant surface glycoprotein ESs, as had previously been shown for TbISWI and NLP. All four proteins are expressed and interact with each other in both major life cycle stages and show similar distributions at Pol I-transcribed loci. They are also found at Pol II strand switch regions as determined with ChIP. ISWI, NLP, RCCP, and FYRP therefore appear to form a single major ISWI complex in T. brucei (TbIC). This reduced complexity of ISWI regulation and the presence of novel ISWI partners highlights the early divergence of trypanosomes in evolution.
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and.
authors.forename: Tara
authors.initials: T
authors.lastname: Stanne
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and.
authors.forename: Mani Shankar
authors.initials: MS
authors.lastname: Narayanan
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and.
authors.forename: Sophie
authors.initials: S
authors.lastname: Ridewood
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ling
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Witmer
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and.
authors.forename: Manish
authors.initials: M
authors.lastname: Kushwaha
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and.
authors.forename: Simone
authors.initials: S
authors.lastname: Wiesler
authors.affiliation: the School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom.
authors.forename: Bill
authors.initials: B
authors.lastname: Wickstead
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wood
authors.affiliation: Division of Cell and Molecular Biology, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom and. Electronic address: gloria.rudenko@imperial.ac.uk.
authors.forename: Gloria
authors.initials: G
authors.lastname: Rudenko
mesh_terms: D000818:Animals; D042002:Chromatin Assembly and Disassembly / Q000235:genetics*; D055785:Gene Knockdown Techniques; D017125:Genes, Protozoan; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics; D054730:Protein Interaction Domains and Motifs; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics; D014158:Transcription, Genetic; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000737:chemistry / Q000235:genetics
chemical_list: D046912:Multiprotein Complexes; D015800:Protozoan Proteins; D014643:Variant Surface Glycoproteins, Trypanosoma
keywords: ISWI; RNA polymerase I; Trypanosoma brucei; VSG expression site; chromatin remodeling; nucleosome; transcription