Solution structure of the general transcription factor 2I domain in mouse TFII-I protein

Abstract

The general transcription factor TFII-I, with the corresponding gene name GTF2I, is an unusual transcriptional regulator that associates with both basal and signal-induced transcription factors. TFII-I consists of six GTF2I repeat domains, called I-repeats R1-R6. The structure and function of the GTF2I domain are not clearly understood, even though it contains a helix-loop-helix motif, which is considered to be the protein-protein interaction area, based on biochemical analyses. Here, we report the solution structure of the fifth repeat of the six GTF2I repeat domains from murine TFII-I, which was determined by heteronuclear multidimensional NMR spectroscopy (PDB code 1Q60). The three-dimensional structure of the GTF2I domain is classified as a new fold, consisting of four helices (residues 8-24, 34-39, 63-71, and 83-91), two antiparallel beta strands (residues 44-47 and 77-80), and a well-defined loop containing two beta-turns between sheet 1 and helix 3. All of the repeats probably have similar folds to that of repeat 5, because the conserved residues in the GTF2I repeat domains are assembled on the hydrophobic core, turns, and secondary structure elements, as revealed by a comparison of the sequences of the first through the sixth GTF2I repeats in TFII-I.

Figure 1.

Overall structure of the GTF2I domain. (A) Stereoview of a trace of the backbone atoms for the ensemble of the 20 lowest energy structures (residues 8–93). (B) Ribbon diagram of the GTF2I domain. A view of the left edge is in the same orientation as in A. As going to the right, the views are rotated by 90° around the vertical axis, respectively. The residues forming the core of the protein are shown for the side-chain heavy atoms. (C) Molecular surface representations of the electrostatic potential (blue, positive; red, negative) of the GTF2I domain, calculated by MOLMOL. The view is in the same orientation as those in B and C.

Figure 2.

(A) Schematic diagram of the mouse BAP-135 protein. The dotted boxes represent the GTF2I domains (denoted as R1–R6). (B) Sequence alignment of each GTF2I repeat domain (R1–R6). The information on “buried” and “accessible” are created by Procheck. The sequence was aligned by ClustalX and displayed by ESPript. The colors are chosen according to the similarity (red box and white character, strict identity; red character, similarity in a group; blue frame, similarity across groups). cGMP-dependent protein kinase Ib-phosphorylated serine residues are marked by green boxes.