RNA polymerase III-specific general transcription factor IIIC contains a heterodimer resembling TFIIF Rap30/Rap74.
Transcription of tRNA-encoding genes by RNA polymerase (Pol) III requires the six-subunit general transcription factor IIIC that uses subcomplexes τA and τB to recognize two gene-internal promoter elements named A- and B-box. The Schizosaccharomyces pombe τA subcomplex comprises subunits Sfc1, Sfc4 and Sfc7. The crystal structure of the Sfc1/Sfc7 heterodimer reveals similar domains and overall domain architecture to the Pol II-specific general transcription factor TFIIF Rap30/Rap74. The N-terminal Sfc1/Sfc7 dimerization module consists of a triple β-barrel similar to the N-terminal TFIIF Rap30/Rap74 dimerization module, whereas the C-terminal Sfc1 DNA-binding domain contains a winged-helix domain most similar to the TFIIF Rap30 C-terminal winged-helix domain. Sfc1 DNA-binding domain recognizes single and double-stranded DNA by an unknown mechanism. Several features observed for A-box recognition by τA resemble the recognition of promoters by bacterial RNA polymerase, where σ factor unfolds double-stranded DNA and stabilizes the non-coding DNA strand in an open conformation. Such a function has also been proposed for TFIIF, suggesting that the observed structural similarity between Sfc1/Sfc7 and TFIIF Rap30/Rap74 might also reflect similar functions.
European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany and UJF-EMBL-CNRS UMI 3265, Unit of Virus Host-Cell Interactions, 38042 Grenoble Cedex 9, France.
Nicholas M I
NM
Taylor
Florence
F
Baudin
Gudrun
G
von Scheven
Christoph W
CW
Müller
D000595:Amino Acid Sequence; D004247:DNA / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry* / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism; D019473:Transcription Factors, TFII / Q000737:chemistry*; D019474:Transcription Factors, TFIII / Q000737:chemistry* / Q000378:metabolism; D000098832:Transcription Factor TFIIIC
D029702:Schizosaccharomyces pombe Proteins; C585204:Sfc1 protein, S pombe; C585205:Sfc7 protein, S pombe; D014157:Transcription Factors; D019473:Transcription Factors, TFII; D019474:Transcription Factors, TFIII; D000098832:Transcription Factor TFIIIC; D004247:DNA; C056604:transcription factor TFIIF