Identification of the ISWI Chromatin Remodeling Complex of the Early Branching Eukaryote Trypanosoma brucei*

Background: Eukaryotes typically encode a range of ISWI chromatin remodeling complexes with different functions. Results:We have identified and analyzed three novel ISWI partners in the early branching eukaryote Trypanosoma brucei. Conclusion: T. brucei appears to have a single major ISWI complex. Significance:This unusually simple ISWI configuration could be a consequence of the relative lack of transcriptional regulation in this ancient eukaryote. 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 uni-cellular parasiteTrypanosoma brucei, which causes African sleep-ing 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 tan-dem affinity purification to determine the interacting partners o