Dynamic colocalization of 2 simultaneously active VSG expression sites within a single expression-site body in Trypanosoma brucei

Title: Dynamic colocalization of 2 simultaneously active VSG expression sites within a single expression-site body in Trypanosoma brucei
Authors: Budzak, J
Kerry, LE
Aristodemou, A
Hall, BS
Witmer, K
Kushwaha, M
Davies, C
Povelones, ML
McDonald, JR
Sur, A
Myler, PJ
Rudenko, G
Item Type: Journal Article
Abstract: Monoallelic exclusion ensures that the African trypanosome Trypanosoma brucei exclusively expresses only 1 of thousands of different variant surface glycoprotein (VSG) coat genes. The active VSG is transcribed from 1 of 15 polycistronic bloodstream-form VSG expression sites (ESs), which are controlled in a mutually exclusive fashion. Unusually, T. brucei uses RNA polymerase I (Pol I) to transcribe the active ES, which is unprecedented among eukaryotes. This active ES is located within a unique extranucleolar Pol I body called the expression-site body (ESB). A stringent restriction mechanism prevents T. brucei from expressing multiple ESs at the same time, although how this is mediated is unclear. By using drug-selection pressure, we generated VSG double-expresser T. brucei lines, which have disrupted monoallelic exclusion, and simultaneously express 2 ESs in a dynamic fashion. The 2 unstably active ESs appear epigenetically similar to fully active ESs as determined by using chromatin immunoprecipitation for multiple epigenetic marks (histones H3 and H1, TDP1, and DNA base J). We find that the double-expresser cells, similar to wild-type single-expresser cells, predominantly contain 1 subnuclear ESB, as determined using Pol I or the ESB marker VEX1. Strikingly, simultaneous transcription of the 2 dynamically transcribed ESs is normally observed only when the 2 ESs are both located within this single ESB. This colocalization is reversible in the absence of drug selection. This discovery that simultaneously active ESs dynamically share a single ESB demonstrates the importance of this unique subnuclear body in restricting the monoallelic expression of VSG.
Issue Date: 13-Aug-2019
Date of Acceptance: 2-Jul-2019
URI: http://hdl.handle.net/10044/1/73083
DOI: https://doi.org/10.1073/pnas.1905552116
ISSN: 0027-8424
Publisher: National Academy of Sciences
Start Page: 16561
End Page: 16570
Journal / Book Title: Proceedings of the National Academy of Sciences of the United States of America
Volume: 116
Issue: 33
Copyright Statement: © 2019 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY) (http://creativecommons.org/licenses/by/4.0/).
Sponsor/Funder: Wellcome Trust
Funder's Grant Number: 212211/Z/18/Z
Keywords: Science & Technology
Multidisciplinary Sciences
Science & Technology - Other Topics
variant surface glycoprotein
RNA polymerase I
antigenic variation
epigenetics
monoallelic exclusion
VARIANT SURFACE GLYCOPROTEIN
RNA-POLYMERASE-I
GENE-EXPRESSION
ANTIGENIC VARIATION
MONOALLELIC EXPRESSION
BASE J
TRANSCRIPTION
LOCALIZATION
HYDROXYMETHYLURACIL
ORGANIZATION
RNA polymerase I
antigenic variation
epigenetics
monoallelic exclusion
variant surface glycoprotein
Science & Technology
Multidisciplinary Sciences
Science & Technology - Other Topics
variant surface glycoprotein
RNA polymerase I
antigenic variation
epigenetics
monoallelic exclusion
VARIANT SURFACE GLYCOPROTEIN
RNA-POLYMERASE-I
GENE-EXPRESSION
ANTIGENIC VARIATION
MONOALLELIC EXPRESSION
BASE J
TRANSCRIPTION
LOCALIZATION
HYDROXYMETHYLURACIL
ORGANIZATION
MD Multidisciplinary
Publication Status: Published
Online Publication Date: 2019-07-29
Appears in Collections:Faculty of Natural Sciences



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