TBP

PF3D7_0506200 (TBP) is the P. falciparum TATA-box-binding protein, a sequence-specific DNA-binding factor that nucleates RNA polymerase transcription preinitiation at gene promoters (PMID:15760658). It is encoded by a single-copy chromosome 5 gene producing a 228-residue protein with the bipartite TBP architecture—a species-specific N-terminal region and a conserved C-terminal domain of two direct ~78-aa repeats flanking a basic core that retains most DNA-contacting residues despite only 42% identity to yeast TBP (PMID:8444340). Recombinant PfTBP binds directly and specifically to a consensus TATA box (TATAA) and a TATA box-like element (TGTAA) upstream of the kahrp and gbp-130 transcription start sites, and native PfTBP associates with these elements in vivo (PMID:15760658). PfTBP is a nuclear protein (PMID:17203999) that, together with PfTFIIE, occupies promoters of both active and inactive erythrocytic-stage genes—but not non-erythrocytic-stage promoters (csp, pfs25)—independently of transcriptional activity and histone H3/H4 acetylation, consistent with a constitutively poised preinitiation complex (PMID:18951895). PfTBP is also a subunit of a P. falciparum TBP-associated-factor (TAF) complex (PMID:31728527). Beyond its DNA-binding specificity, promoter occupancy, and complex membership, the mechanistic details of how PfTBP directs stage-specific transcription have not been characterized in the available corpus.

1. 1993 Medium

   Establishing whether P. falciparum encodes a bona fide TATA-binding protein was the first step in defining the parasite's basal transcription machinery; isolating the gene showed it exists as a single-copy locus with the conserved TBP fold.

   Evidence Gene isolation, sequencing, and comparative sequence/hydropathy analysis of a chromosome 5 locus

   PMID:8444340

   Open questions at the time

   • DNA binding inferred from sequence conservation only, not tested functionally
   • N-terminal species-specific domain function unknown
   • no evidence of promoter recognition or partner interactions
2. 2005 High

   Whether PfTBP actually recognizes parasite promoter elements was unresolved; direct binding assays demonstrated specific recognition of both consensus and TATA-like sequences in native gene promoters in vitro and in vivo.

   Evidence Supershift and DNase I footprinting with recombinant GST-PfTBP plus ChIP with native protein on kahrp and gbp-130 promoters

   PMID:15760658

   Open questions at the time

   • does not establish requirement of PfTBP binding for transcription initiation
   • limited to two promoters
   • no structural model of the PfTBP-DNA complex
3. 2006 Medium

   Confirming the subcellular compartment where PfTBP acts was needed to place it in the transcription machinery; antibody-based detection localized native PfTBP to the parasite nucleus.

   Evidence Western blotting and immunofluorescence with a PfTBP-specific monoclonal antibody (Pf.r1) on nuclear extracts

   PMID:17203999

   Open questions at the time

   • no functional consequence of localization tested
   • does not resolve dynamics across the erythrocytic cycle
4. 2008 Medium

   It was unknown whether PfTBP occupancy tracks with active transcription or reflects a poised state; genome-region ChIP showed PfTBP and PfTFIIE occupy both active and inactive erythrocytic promoters independently of transcriptional activity and histone acetylation.

   Evidence ChIP for PfTBP and PfTFIIE across multiple stage-specific promoters, coding and 3' regions in erythrocytic-stage parasites

   PMID:18951895

   Open questions at the time

   • mechanism maintaining the poised complex unresolved
   • no in vitro reconstitution of the preinitiation complex
   • does not explain how stage-specific transcription is triggered from poised promoters
5. 2019 Medium

   Whether PfTBP operates within a defined multiprotein assembly was addressed by interaction proteomics, which placed PfTBP as a subunit of a P. falciparum TBP-associated-factor (TAF) complex.

   Evidence Tagging and quantitative interaction proteomics (mass spectrometry) with tagged bait proteins

   PMID:31728527

   Open questions at the time

   • functional role of PfTBP within the TAF complex not directly tested
   • no structural organization of the complex defined
   • individual TAF subunit contributions to PfTBP function unresolved

• How PfTBP directs stage-specific and gene-specific transcription—the transition from poised preinitiation complexes to productive initiation and the roles of individual TAF partners—remains unresolved.
• no reconstitution of PfTBP-directed transcription initiation
• no genetic loss-of-function analysis of PfTBP in the corpus
• no structural model of PfTBP alone or in the TAF complex