GTF2F2

GTF2F2 (RAP30) is the small subunit of the general transcription factor TFIIF, which it forms by heterodimerization with RAP74 to enable accurate, promoter-specific transcription initiation by RNA polymerase II from both TATA-containing and TATA-less promoters (PMID:3380090). RAP30 carries the polymerase-binding activity of the complex: it contacts RNA pol II directly through subunit RPB5, an interaction mediated by its middle region and abolished by point mutations Y124A and Q131A (PMID:11278533), and it suppresses nonspecific pol II–DNA binding so that polymerase is delivered to promoters rather than bulk DNA (PMID:1729606). Together with TBP and TFIIB, RAP30 constitutes the minimal set sufficient for stable promoter recognition by pol II (PMID:1577790), and it is specifically required for forming the Sarkosyl-resistant preinitiation complex, defining it as an initiation factor (whereas its RAP74 partner acts in promoter escape and elongation) (PMID:8376403). RAP30 bridges the basal machinery through an N-terminal region that binds TFIIB (PMID:8662660) and through direct contact with the TFIID component hTAFII100 (PMID:8758937). Its C-terminal domain is a cryptic winged helix-turn-helix DNA-binding module structurally homologous to linker histone H5 and to sigma70 region 4, with the DNA-binding surface required for transcription (PMID:7937895, PMID:9689043), while its dimerization interface with RAP74 adopts a triple-barrel fold (PMID:11183778). Association with Tat-SF1 links RAP30 to elongation control as well (PMID:10454543). A single low-confidence study reports that GTF2F2 promotes epithelial-mesenchymal transition in an ovarian cancer cell line (PMID:40442848).

1. 1988 High

   Established TFIIF as a RAP30/RAP74 heterodimer essential for accurate pol II initiation, answering what cellular activity these polymerase-associated proteins carry.

   Evidence Affinity chromatography and reconstituted in vitro transcription from multiple promoters

   PMID:3380090

   Open questions at the time

   • Did not resolve which subunit contacts polymerase versus DNA
   • No structural information on the complex
2. 1991 High

   Identified a sigma70-homologous polymerase-binding region in RAP30, explaining the molecular basis for its pol II association by analogy to bacterial sigma factors.

   Evidence Sequence analysis, in vitro phosphorylation protection, and competition binding against E. coli RNA polymerase/sigma70

   PMID:1652156

   Open questions at the time

   • Functional analogy inferred from cross-species binding, not direct structural homology at the time
   • Did not map residues required for pol II contact
3. 1992 High

   Showed RAP30 alone binds pol II and suppresses nonspecific DNA binding, and that TBP+TFIIB+RAP30 form the minimal promoter-recognition set, assigning RAP30 a defined role in directing polymerase to promoters.

   Evidence Recombinant protein binding, DNA-binding competition, and minimal-set reconstitution assays

   PMID:1577790 PMID:1729606

   Open questions at the time

   • Mechanism of nonspecific-binding suppression not structurally defined
   • Did not separate initiation from elongation roles
4. 1992 High

   Mapped the C-terminal sigma region 4.2-like sequence as required for pol II interaction, separating dimerization from polymerase contact.

   Evidence Deletion mutagenesis and biochemical interaction assays

   PMID:1429731

   Open questions at the time

   • No high-resolution structure of the interaction surface
   • Did not identify pol II subunit contacted
5. 1993 High

   Dissected the division of labor within TFIIF, defining RAP30 as an initiation factor required for the Sarkosyl-resistant preinitiation complex while RAP74 drives promoter escape.

   Evidence Sarkosyl-resistance and pulse-chase in vitro transcription with recombinant subunits

   PMID:8376403

   Open questions at the time

   • 1994 work later attributed elongation/PIC contributions to both subunits, partially refining this clean split
   • Molecular events distinguishing the two steps not resolved
6. 1994 High

   Revealed a cryptic sigma70 region 4-like DNA-binding domain in the RAP30 C terminus whose DNA binding is required for transcription, linking a structural element to function.

   Evidence Fusion-protein DNA-binding assays, deletion mutagenesis, and in vitro transcription

   PMID:7929273 PMID:7937895

   Open questions at the time

   • Why the activity is masked in intact RAP30 not explained
   • DNA target sequence specificity unresolved
7. 1995 Medium

   Mapped RAP30 functional architecture in the Drosophila ortholog, assigning RAP74 dimerization to the N-terminus and pol II interaction/partial activity to the C-terminus.

   Evidence Glycerol gradient sedimentation and reconstituted transcription with deletion mutants (Drosophila ortholog)

   PMID:7890767

   Open questions at the time

   • Domain assignments from ortholog require human confirmation
   • Basis of ~50% C-terminal activity not explained
8. 1996 Medium

   Defined how RAP30 connects to the rest of the basal machinery, showing direct binding to TFIIB and to the TFIID subunit hTAFII100.

   Evidence Deletion mapping, GST pulldown/co-IP, antibody inhibition, and in vitro transcription

   PMID:8662660 PMID:8758937

   Open questions at the time

   • hTAFII100 interaction supported by single-lab co-IP plus antibody inhibition
   • Stoichiometry of these contacts in the assembled PIC unknown
9. 1998 High

   Solved the RAP30 DNA-binding domain structure as a winged helix homologous to linker histone H5, providing a structural rationale for a PIC condensation role.

   Evidence Multinuclear NMR with DNA-binding surface identification

   PMID:9689043

   Open questions at the time

   • Condensation-factor model is structural inference, not directly demonstrated functionally
   • No DNA-bound complex structure
10. 1999 Medium

    Linked RAP30 specifically to elongation control through subunit-selective association with Tat-SF1.

    Evidence Co-immunoprecipitation from nuclear extracts and in vivo overexpression transcription assay

    PMID:10454543

    Open questions at the time

    • Single-lab co-IP; direct binding region not mapped
    • Functional consequence beyond Tat-specific transcription unclear
11. 2001 High

    Identified RPB5 as the key pol II contact for TFIIF and pinpointed RAP30 residues Y124 and Q131 required for the interaction, defining the molecular interface for TFIIF–polymerase association.

    Evidence In vitro pulldown, co-IP in COS1 cells, and alanine-scanning mutagenesis

    PMID:11278533

    Open questions at the time

    • Interface not resolved by structure
    • How RPB5 contact integrates with the C-terminal DNA-binding domain unknown
12. 2005 High

    Mapped the reciprocal RPB5 residues critical for RAP30 binding and showed overlap with the hepatitis B X protein site, defining the contact from the polymerase side.

    Evidence Two-step alanine-scanning mutagenesis with in vitro binding and co-IP in mammalian cells

    PMID:16169872

    Open questions at the time

    • Functional consequence of HBx competition for transcription not established here
    • No co-crystal of the RAP30–RPB5 interface
13. 2025 Low

    Tested a cellular phenotype, reporting that GTF2F2 promotes migration, invasion, and EMT in an ovarian cancer cell line.

    Evidence siRNA/shRNA knockdown, migration/invasion assays, and Western blot for EMT markers in ES-2 cells

    PMID:40442848

    Open questions at the time

    • Single cell line, single lab phenotype without mechanistic pathway placement
    • EMT effect not connected to RAP30's basal transcription function
    • No rescue or in vivo validation

• How RAP30's general transcription-initiation role is harnessed to regulate specific gene programs such as those driving EMT remains unresolved.
• No structure of RAP30 within an assembled human PIC
• No identification of target genes whose transcription depends on RAP30 in physiological contexts