Electron crystal structure of the transcription factor and DNA repair complex, core TFIIH

Core TFIIH from yeast, made up of five subunits required both for RNA polym erase II transcription and nucleotide excision DNA repair, formed 2D crysta ls on charged lipid layers. Diffraction from electron micrographs of the cr ystals in negative stain extended to about 13 Angstrom resolution, and 3D r econstruction revealed several discrete densities whose volumes corresponde d well with those of individual TFIIH subunits. The structure is based on a ring of three subunits, Tfb1, Tfb2, and Tfb3, to which are appended severa l functional moieties: Rad3, bridged to Tfb1 by SsI1; SsI2, known to intera ct with Tfb2; and Kin28, known to interact with Tfb3.