scholarly journals Trypanosoma brucei ATR Links DNA Damage Signaling during Antigenic Variation with Regulation of RNA Polymerase I-Transcribed Surface Antigens

Cell Reports ◽  
2020 ◽  
Vol 30 (3) ◽  
pp. 836-851.e5 ◽  
Author(s):  
Jennifer Ann Black ◽  
Kathryn Crouch ◽  
Leandro Lemgruber ◽  
Craig Lapsley ◽  
Nicholas Dickens ◽  
...  
Keyword(s):  
Dna Damage ◽  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Surface Antigens ◽  
Rna Polymerase I ◽  
Dna Damage Signaling ◽  
Polymerase I

scholarly journals Active RNA Polymerase I of Trypanosoma brucei Harbors a Novel Subunit Essential for Transcription

2007 ◽  
Vol 27 (17) ◽  
pp. 6254-6263 ◽  
Author(s):  
Tu N. Nguyen ◽  
Bernd Schimanski ◽  
Arthur Günzl
Keyword(s):  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Surface Antigens ◽  
Amino Acid Sequences ◽  
Rna Polymerase I ◽  
Surface Glycoprotein ◽  
Sequence Motif ◽  
Cell Surface Antigens ◽  
Conserved Sequence ◽  
Polymerase I

ABSTRACT A unique characteristic of the protistan parasite Trypanosoma brucei is a multifunctional RNA polymerase I which, in addition to synthesizing rRNA as in other eukaryotes, transcribes gene units encoding the major cell surface antigens variant surface glycoprotein and procyclin. Thus far, purification of this enzyme has revealed nine orthologues of known subunits but no active enzyme. Here, we have epitope tagged the specific subunit RPB6z and tandem affinity purified RNA polymerase I from crude extract. The purified enzyme was active in both a nonspecific and a promoter-dependent transcription assay and exhibited enriched protein bands with apparent sizes of 31, 29, and 27 kDa. p31 and its trypanosomatid orthologues were identified, but their amino acid sequences have no similarity to proteins of other eukaryotes, nor do they contain a conserved sequence motif. Nevertheless, p31 cosedimented with purified RNA polymerase I, and RNA interferance-mediated silencing of p31 was lethal, affecting the abundance of rRNA. Moreover, extract of p31-silenced cells exhibited a specific defect in transcription of class I templates, which was remedied by the addition of purified RNA polymerase I, and an anti-p31 serum completely blocked RNA polymerase I-mediated transcription. We therefore dubbed this novel functional component of T. brucei RNA polymerase I TbRPA31.

scholarly journals Quantification of RNA Polymerase I transcriptional attenuation at the active VSG expression site in Trypanosoma brucei

2021 ◽  
Author(s):  
Nadine Weisert ◽  
Klara Thein ◽  
Helena Reis ◽  
Christian J Janzen
Keyword(s):  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Rna Polymerase I ◽  
Surface Glycoprotein ◽  
Transcriptional Elongation ◽  
Pol I ◽  
Expression Site ◽  
Polymerase I ◽  
Large Repertoire

The cell surface of the extracellular pathogen Trypanosoma brucei consists of a dense coat of variant surface glycoprotein (VSG), which enables the parasite to evade the immune system of the vertebrate host. Only one VSG gene from a large repertoire is expressed from a so-called bloodstream form expression site (BES) at a given timepoint. There are several BES in every parasite but only one is transcriptionally active. Other BES are silenced by transcriptional attenuation. Periodic activation of a previously-silenced BES results in differential VSG transcription and escape from the immune response. A process called antigenic variation. In contrast to gene transcription in other eukaryotes, the BES is transcribed by RNA polymerase I (Pol I). It was proposed that this highly-processive polymerase is needed to provide a sufficiently high transcription rate at the VSG gene. Surprisingly, we discovered a position-dependent Pol I activity and attenuation of transcriptional elongation also at the active BES. Transcription rates at the VSG gene appear to be comparable to Pol II-mediated transcription of house-keeping genes. Although these findings are in contradiction to the long-standing concept of continuously high transcription rates at the active BES in Trypanosoma brucei, they are complementary to recent groundbreaking findings about transcriptional regulation of VSG genes.

scholarly journals Characterization of a Novel Class I Transcription Factor A (CITFA) Subunit That Is Indispensable for Transcription by the Multifunctional RNA Polymerase I of Trypanosoma brucei

2012 ◽  
Vol 11 (12) ◽  
pp. 1573-1581 ◽  
Author(s):  
Tu N. Nguyen ◽  
Bao N. Nguyen ◽  
Ju Huck Lee ◽  
Aswini K. Panigrahi ◽  
Arthur Günzl
Keyword(s):  
Transcription Factor ◽  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Rna Polymerase I ◽  
Class I ◽  
Mammalian Host ◽  
Subunit Structure ◽  
Content Type ◽  
Pol I ◽  
Polymerase I

ABSTRACT Trypanosoma brucei is the only organism known to have evolved a multifunctional RNA polymerase I (pol I) system that is used to express the parasite's ribosomal RNAs, as well as its major cell surface antigens, namely, the variant surface glycoprotein (VSG) and procyclin, which are vital for establishing successful infections in the mammalian host and the tsetse vector, respectively. Thus far, biochemical analyses of the T. brucei RNA pol I transcription machinery have elucidated the subunit structure of the enzyme and identified the class I transcription factor A (CITFA). CITFA binds to RNA pol I promoters, and its CITFA-2 subunit was shown to be absolutely essential for RNA pol I transcription in the parasite. Tandem affinity purification (TAP) of CITFA revealed the subunits CITFA-1 to -6, which are conserved only among kinetoplastid organisms, plus the dynein light chain DYNLL1. Here, by tagging CITFA-6 instead of CITFA-2, a complex was purified that contained all known CITFA subunits, as well as a novel proline-rich protein. Functional studies carried out in vivo and in vitro , as well as a colocalization study, unequivocally demonstrated that this protein is a bona fide CITFA subunit, essential for parasite viability and indispensable for RNA pol I transcription of ribosomal gene units and the active VSG expression site in the mammalian-infective life cycle stage of the parasite. Interestingly, CITFA-7 function appears to be species specific, because expression of an RNA interference (RNAi)-resistant CITFA-7 transgene from Trypanosoma cruzi could not rescue the lethal phenotype of silencing endogenous CITFA-7 .

RNA polymerase I-mediated protein-coding gene expression in Trypanosoma brucei

1992 ◽  
Vol 8 (12) ◽  
pp. 414-418 ◽  
Author(s):  
H-M. Chung ◽  
M.G-S. Lee ◽  
L.H.T. Van der Ploeg
Keyword(s):  
Gene Expression ◽  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Rna Polymerase I ◽  
Protein Coding ◽  
Polymerase I

scholarly journals A New Strategy of RNA Interference That Targets Heterologous Sequences Reveals CITFA1 as an Essential Component of Class I Transcription Factor A in Trypanosoma brucei

2014 ◽  
Vol 13 (6) ◽  
pp. 785-795 ◽  
Author(s):  
Sung Hee Park ◽  
Bao N. Nguyen ◽  
Justin K. Kirkham ◽  
Tu N. Nguyen ◽  
Arthur Günzl
Keyword(s):  
Transcription Factor ◽  
Rna Interference ◽  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Transcription Initiation ◽  
Single Copy ◽  
Rna Polymerase I ◽  
Class I ◽  
Content Type ◽  
Polymerase I

ABSTRACTConditional gene silencing by RNA interference inTrypanosoma bruceican be inconclusive if knockdowns are inefficient or have off-target effects. To enable efficient, specific silencing of single-copy genes in mammalian-infective, bloodstream form trypanosomes, we developed a system that targets the heterologous and functionalTrypanosoma cruziU2AF353′ untranslated region (UTR) (Tc3) or, alternatively, the sequence of the PTP tag, which can be fused to any mRNA of interest. Two cell lines were created, single-marker Tc3 (smTc3) and smPTP, which conditionally express Tc3 and PTP double-stranded RNA (dsRNA), respectively. The system depends on manipulating both alleles of the gene of interest so that cells exclusively express the target mRNA as a fusion to one of these heterologous sequences. We generated allele integration vectors in which the C-terminal part of a gene's coding sequence can be fused to either heterologous sequence in a single cloning step. We first tested this system withCITFA7, which encodes a well-characterized subunit of the class I transcription factor A (CITFA), an essential factor for transcription initiation by RNA polymerase I. Targeting either Tc3 or PTP fused to theCITFA7mRNA resulted in gene knockdowns that were as efficient and specific as targeting the endogenousCITFA7mRNA. Moreover, application of this system toCITFA1, which could not be silenced by established methods, demonstrated that the gene encodes an essential CITFA subunit that mediates binding of the transcription factor complex to RNA polymerase I promoters.

Purification of an eight subunit RNA polymerase I complex in Trypanosoma brucei

2006 ◽  
Vol 149 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Tu N. Nguyen ◽  
Bernd Schimanski ◽  
André Zahn ◽  
Birgit Klumpp ◽  
Arthur Günzl
Keyword(s):  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Rna Polymerase I ◽  
Polymerase I

Characterization of subunits of the RNA polymerase I complex in Trypanosoma brucei

2005 ◽  
Vol 139 (2) ◽  
pp. 249-260 ◽  
Author(s):  
David Walgraffe ◽  
Sara Devaux ◽  
Laurence Lecordier ◽  
Jean-François Dierick ◽  
Marc Dieu ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Rna Polymerase I ◽  
Polymerase I

scholarly journals Complete sequence of the gene encoding the largest subunit of RNA polymerase I of Trypanosoma brucei

FEBS Letters ◽  
1989 ◽  
Vol 249 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Waldemar Jess ◽  
Andrea Hammer ◽  
Albert W.C.A. Cornelissen
Keyword(s):  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Complete Sequence ◽  
Rna Polymerase I ◽  
Gene Encoding ◽  
Polymerase I

scholarly journals The chemotherapeutic agent CX-5461 irreversibly blocks RNA polymerase I initiation and promoter release to cause nucleolar disruption, DNA damage and cell inviability

NAR Cancer ◽  
2020 ◽  
Vol 2 (4) ◽  
Author(s):  
Jean-Clément Mars ◽  
Michel G Tremblay ◽  
Mélissa Valere ◽  
Dany S Sibai ◽  
Marianne Sabourin-Felix ◽  
...  
Keyword(s):  
Dna Damage ◽  
Rna Polymerase ◽  
Ribosomal Rna ◽  
Transcription Initiation ◽  
Ribosome Biogenesis ◽  
Chemotherapeutic Agent ◽  
Rna Polymerase I ◽  
Initiation Complex ◽  
Promoter Recruitment ◽  
Polymerase I

Abstract In the search for drugs to effectively treat cancer, the last 10 years have seen a resurgence of interest in targeting ribosome biogenesis. CX-5461 is a potential inhibitor of ribosomal RNA synthesis that is now showing promise in phase I trials as a chemotherapeutic agent for a range of malignancies. Here, we show that CX-5461 irreversibly inhibits ribosomal RNA transcription by arresting RNA polymerase I (RPI/Pol1/PolR1) in a transcription initiation complex. CX-5461 does not achieve this by preventing formation of the pre-initiation complex nor does it affect the promoter recruitment of the SL1 TBP complex or the HMGB-box upstream binding factor (UBF/UBTF). CX-5461 also does not prevent the subsequent recruitment of the initiation-competent RPI–Rrn3 complex. Rather, CX-5461 blocks promoter release of RPI–Rrn3, which remains irreversibly locked in the pre-initiation complex even after extensive drug removal. Unexpectedly, this results in an unproductive mode of RPI recruitment that correlates with the onset of nucleolar stress, inhibition of DNA replication, genome-wide DNA damage and cellular senescence. Our data demonstrate that the cytotoxicity of CX-5461 is at least in part the result of an irreversible inhibition of RPI transcription initiation and hence are of direct relevance to the design of improved strategies of chemotherapy.

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