Crystal structure of the C-terminal domain of the RAP74 subunit of human transcription factor IIF

The x-ray structure of a C-terminal fragment of the RAP74 subunit of human transcription factor (TF) IIF has been determined at 1.02-Angstrom resoluti on. The alpha/beta structure is strikingly similar to the globular domain o f linker histone H5 and the DNA-binding domain of hepatocyte nuclear factor 3 gamma (HNF-3 gamma), making it a winged-helix protein, The surface elect rostatic properties of this compact domain differ significantly from those of bona fide winged-helix transcription factors (HNF-3 gamma RFX1) and from the winged-helix domains found within the RAP30 subunit of TFIIF and the b eta subunit of TFIIE, RAP74 has been shown to interact with the TFIIF-assoc iated C-terminal domain phosphatase FCP1, and a putative phosphatase bindin g site has been identified within the RAP74 winged-helix domain.