A divergent transcription factor TFIIB in trypanosomes is required for RNA polymerase II-dependent spliced leader RNA transcription and cell viability.
Transcription by RNA polymerase II in trypanosomes deviates from the standard eukaryotic paradigm. Genes are transcribed polycistronically and subsequently cleaved into functional mRNAs, requiring trans splicing of a capped 39-nucleotide leader RNA derived from a short transcript, the spliced leader (SL) RNA. The only identified trypanosome RNA polymerase II promoter is that of the SL RNA gene. We have previously shown that transcription of SL RNA requires divergent trypanosome homologs of RNA polymerase II, TATA binding protein, and the small nuclear RNA (snRNA)-activating protein complex. In other eukaryotes, TFIIB is an additional key component of transcription for both mRNAs and polymerase II-dependent snRNAs. We have identified a divergent homolog of the usually highly conserved basal transcription factor, TFIIB, from the pathogenic parasite Trypanosoma brucei. T. brucei TFIIB (TbTFIIB) interacted directly with the trypanosome TATA binding protein and RNA polymerase II, confirming its identity. Functionally, in vitro transcription studies demonstrated that TbTFIIB is indispensable in SL RNA gene transcription. RNA interference (RNAi) studies corroborated the essential nature of TbTFIIB, as depletion of this protein led to growth arrest of parasites. Furthermore, nuclear extracts prepared from parasites depleted of TbTFIIB, after the induction of RNAi, required recombinant TbTFIIB to support spliced leader transcription. The information gleaned from TbTFIIB studies furthers our understanding of SL RNA gene transcription and the elusive overall transcriptional processes in trypanosomes.
Department of Microbiology and Molecular Genetics, UMDNJ-NJ Medical School, International Center for Public Health, 225 Warren St., Newark, NJ 07103, USA.
Jennifer B
JB
Palenchar
Wenzhe
W
Liu
Peter M
PM
Palenchar
Vivian
V
Bellofatto
D000595:Amino Acid Sequence; D000818:Animals; D002470:Cell Survival; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000378:metabolism*; D020038:RNA, Spliced Leader / Q000235:genetics*; D035181:TATA-Box Binding Protein; D035581:Transcription Factor TFIIB / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics*; D014346:Trypanosoma brucei brucei / Q000166:cytology* / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
D020038:RNA, Spliced Leader; D035181:TATA-Box Binding Protein; D035581:Transcription Factor TFIIB; D012319:RNA Polymerase II