Document Detail

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.
MedLine Citation:
PMID:  23104567     Owner:  NLM     Status:  MEDLINE    
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.
Tu N Nguyen; Bao N Nguyen; Ju Huck Lee; Aswini K Panigrahi; Arthur Günzl
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2012-10-26
Journal Detail:
Title:  Eukaryotic cell     Volume:  11     ISSN:  1535-9786     ISO Abbreviation:  Eukaryotic Cell     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-11-29     Completed Date:  2013-05-09     Revised Date:  2013-07-11    
Medline Journal Info:
Nlm Unique ID:  101130731     Medline TA:  Eukaryot Cell     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1573-81     Citation Subset:  IM    
Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, Connecticut, USA.
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MeSH Terms
Amino Acid Sequence
Dyneins / metabolism
Molecular Sequence Data
Protein Subunits / isolation & purification,  metabolism*
Protozoan Proteins / isolation & purification,  metabolism*
RNA Polymerase I / metabolism*
Transcription Factors / isolation & purification,  metabolism*
Transcription, Genetic*
Trypanosoma brucei brucei / enzymology,  genetics,  metabolism*
Grant Support
Reg. No./Substance:
0/Protein Subunits; 0/Protozoan Proteins; 0/Transcription Factors; EC 2.7.7.-/RNA Polymerase I; EC

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