title: Spliced leader RNA gene transcription in Trypanosoma brucei requires transcription factor TFIIH.
abstract: Trypanosomatid parasites share a gene expression mode which differs greatly from that of their human and insect hosts. In these unicellular eukaryotes, protein-coding genes are transcribed polycistronically and individual mRNAs are processed from precursors by spliced leader (SL) trans splicing and polyadenylation. In trans splicing, the SL RNA is consumed through a transfer of its 5'-terminal part to the 5' end of mRNAs. Since all mRNAs are trans spliced, the parasites depend on strong and continuous SL RNA synthesis mediated by RNA polymerase II. As essential factors for SL RNA gene transcription in Trypanosoma brucei, the general transcription factor (GTF) IIB and a complex, consisting of the TATA-binding protein-related protein 4, the small nuclear RNA-activating protein complex, and TFIIA, were recently identified. Although T. brucei TFIIA and TFIIB are extremely divergent to their counterparts in other eukaryotes, their characterization suggested that trypanosomatids do form a class II transcription preinitiation complex at the SL RNA gene promoter and harbor orthologues of other known GTFs. TFIIH is a GTF which functions in transcription initiation, DNA repair, and cell cycle control. Here, we investigated whether a T. brucei TFIIH is important for SL RNA gene transcription and found that silencing the expression of the highly conserved TFIIH subunit XPD in T. brucei affected SL RNA gene synthesis in vivo, and depletion of this protein from extract abolished SL RNA gene transcription in vitro. Since we also identified orthologues of the TFIIH subunits XPB, p52/TFB2, and p44/SSL1 copurifying with TbXPD, we concluded that the parasite harbors a TFIIH which is indispensable for SL RNA gene transcription.
authors.affiliation: Department of Genetics and Developmental Biology, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3301, USA.
authors.forename: Ju Huck
authors.initials: JH
authors.lastname: Lee
authors.forename: Tu N
authors.initials: TN
authors.lastname: Nguyen
authors.forename: Bernd
authors.initials: B
authors.lastname: Schimanski
authors.forename: Arthur
authors.initials: A
authors.lastname: Günzl
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D020868:Gene Silencing; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics; D021381:Protein Transport; D020038:RNA, Spliced Leader / Q000096:biosynthesis* / Q000235:genetics*; D051758:Transcription Factor TFIIH / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D051759:Xeroderma Pigmentosum Group D Protein / Q000302:isolation & purification
chemical_list: D021122:Protein Subunits; D020038:RNA, Spliced Leader; D051758:Transcription Factor TFIIH; D051759:Xeroderma Pigmentosum Group D Protein