title: Base J and H3.V Regulate Transcriptional Termination in Trypanosoma brucei.
abstract: Trypanosoma brucei is a protozoan parasite that lacks many transcription factors found in other eukaryotes, such as those whose binding demarcates enhancers. T. brucei retains histone variants and modifications, however, and it is hypothesized that it relies on epigenetic marks to define transcription-related boundaries. The histone H3 variant (H3.V) and an alternate nucleotide, base J (ß-D-glucosyl-hydroxymethyluracil), are two chromatin marks found at both transcription termination sites (TTSs) and telomeres. Here, we report that the absence of both base J and H3.V result in transcription readthrough and the appearance of antisense transcripts near TTSs. Additionally, we find that maintaining the transcriptional silencing of pol I-transcribed telomeric Variant Surface Glycoprotein (VSG) genes appears to be dependent on deposition of H3.V alone. Our study reveals that gene expression depends on different epigenetic cues depending on chromosomal location and on the transcribing polymerase. This work provides insight into how these signals may have evolved into the more nuanced and fine-tuned gene regulatory mechanisms observed in other model systems.
authors.affiliation: Laboratory of Lymphocyte Biology, The Rockefeller University, New York, New York, United States of America.
authors.forename: Danae
authors.initials: D
authors.lastname: Schulz
authors.affiliation: Laboratory of Lymphocyte Biology, The Rockefeller University, New York, New York, United States of America.
authors.forename: Maryam
authors.initials: M
authors.lastname: Zaringhalam
authors.affiliation: Laboratory of Lymphocyte Biology, The Rockefeller University, New York, New York, United States of America.
authors.forename: F Nina
authors.initials: FN
authors.lastname: Papavasiliou
authors.affiliation: Laboratory of Lymphocyte Biology, The Rockefeller University, New York, New York, United States of America.
authors.forename: Hee-Sook
authors.initials: HS
authors.lastname: Kim
mesh_terms: D002843:Chromatin / Q000235:genetics; D005786:Gene Expression Regulation; D005960:Glucosides / Q000235:genetics; D006657:Histones / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012318:RNA Polymerase I / Q000235:genetics; D016615:Telomere / Q000235:genetics; D014158:Transcription, Genetic; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D014498:Uracil / Q000031:analogs & derivatives; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000235:genetics*
chemical_list: D002843:Chromatin; D005960:Glucosides; D006657:Histones; D014643:Variant Surface Glycoproteins, Trypanosoma; C084880:5-((glucopyranosyloxy)methyl)uracil; D014498:Uracil; D012318:RNA Polymerase I