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The heterodimeric transcription factor E2F1-DP1 plays crucial roles in coordinating gene expression during G1/S cell cycle progression. For transcriptional activation, the transactivation domain (TAD) of E2F1 is known to interact with the TATA-binding protein of TFIID and the p62 subunit of TFIIH. It is generally believed that DP1 facilitates E2F1 binding to target DNA and does not possess a TAD. Here, we show that an acidic region of DP1, whose function has remained elusive, binds to the plekstrin homology (PH) domain of p62 with higher affinity than that of E2F1 and contributes to transcriptional activation. The structure of the complex revealed that DP1 forms a twisted U-shaped, string-like conformation and binds to the surface of the PH domain by anchoring Phe403 into a pocket in the PH domain. The transcriptional activity of E2F1-DP1 was reduced when Phe403 of DP1 was mutated. These findings indicate that the acidic region of DP1 acts as a TAD by contacting TFIIH.

General transcription factor II E (TFIIE) contains an acid-rich region (residues 378–393) in its α -subunit, comprising 13 acidic and two hydrophobic (Phe387 and Val390) residues. Upon binding to the p62 subunit of TFIIH, the acidic region adopts an extended string-like structure on the basic groove of the pleckstrin homology domain (PHD) of p62, and inserts Phe387 and Val390 into two shallow pockets in the groove. Here, we have examined the dynamics of this interaction by NMR and molecular dynamics (MD) simulations. Although alanine substitution of Phe387 and/or Val390 greatly reduced binding to PHD, the binding mode of the mutants was similar to that of the wild-type, as judged by the chemical-shift changes of the PHD. NMR relaxation dispersion profiles of the interaction exhibited large amplitudes for residues in the C-terminal half-string in the acidic region (Phe387, Glu388, Val390, Ala391, and Asp392), indicating a two-site binding mode: one corresponding to the final complex structure, and one to an off-pathway minor complex. To probe the off-pathway complex structure, an atomically detailed free-energy landscape of the binding mode was computed by all-atom multicanonical MD. The most thermodynamically stable cluster corresponded to the final complex structure. One of the next stable clusters was the off-pathway structure cluster, showing the reversed orientation of the C-terminal half-string on the PHD groove, as compared with the final structure. MD calculations elucidated that the C-terminal half-acidic-string forms encounter complexes mainly around the positive groove region with nearly two different orientations of the string, parallel and antiparallel to the final structure. Interestingly, the most encountered complexes exhibit a parallel-like orientation, suggesting that the string has a tendency to bind around the groove in the proper orientation with the aid of Phe387 and/or Val390 to proceed smoothly to the final complex structure.

The global genome nucleotide excision repair factor XPC firstly detects DNA lesions and then recruits a ten-subunit complex TFIIH through binding to the subunit p62 to unwind the damaged DNA for excision repair. This data article contains detailed nuclear magnetic resonance (NMR) restraints (nuclear Overhauser enhancement (NOE)-derived distance restraints, dihedral angle restraints, and hydrogen bond restraints) used for the structure determination of the complex formed between the intrinsically disordered acidic region of XPC and the pleckstrin homology (PH) domain of TFIIH p62, related to the recent work entitled “Structural insight into the mechanism of TFIIH recognition by the acidic string of the nucleotide excision repair factor XPC.” [1].

SummaryIn global genome repair (GGR), XPC detects damaged nucleotides and recruits TFIIH complex. The small acidic region of XPC binds to the pleckstrin homology (PH) domain of TFIIH subunit p62; however, the recognition mechanism remains elusive. Here, we use nuclear magnetic resonance to present the tertiary structure of XPC bound to the PH domain. The XPC acidic region forms a long string stabilized by insertion of Trp133 and Val136 into two separate hollows of the PH domain, coupled with extensive electrostatic contacts. Analysis of several XPC mutants revealed that particularly Trp133 is essential for binding to the PH domain. In cell lines stably expressing mutant XPC, alanine substitution at Trp133 or Trp133/Val136 compromised UV resistance, recruitment of TFIIH to DNA damage, and removal of UV-induced photoproducts from genomic DNA. These findings show how TFIIH complex is recruited by XPC to damaged DNA, advancing our understanding of the early stage of GGR.

Chromodomains are methylated histone binding modules that have been widely studied. Interestingly, some chromodomains are reported to bind to RNA and/or DNA, although the molecular basis of their RNA/DNA interactions has not been solved. Here we propose a novel binding mode for chromodomain-RNA interactions. Essential Sas-related acetyltransferase 1 (Esa1) contains a presumed chromodomain in addition to a histone acetyltransferase domain. We initially determined the solution structure of the Esa1 presumed chromodomain and showed it to consist of a well-folded structure containing a five-stranded beta-barrel similar to the tudor domain rather than the canonical chromodomain. Furthermore, the domain showed no RNA/DNA binding ability. Because the N-terminus of the protein forms a helical turn, we prepared an N-terminally extended construct, which we surprisingly found to bind to poly(U) and to be critical for in vivo function. This extended protein contains an additional beta-sheet that acts as a knot for the tudor domain and binds to oligo(U) and oligo(C) with greater affinity compared with other oligo-RNAs and DNAs examined thus far. The knot does not cause a global change in the core structure but induces a well-defined loop in the tudor domain itself, which is responsible for RNA binding. We made 47 point mutants in an esa1 mutant gene in yeast in which amino acids of the Esa1 knotted tudor domain were substituted to alanine residues and their functional abilities were examined. Interestingly, the knotted tudor domain mutations that were lethal to the yeast lost poly(U) binding ability. Amino acids that are related to RNA interaction sites, as revealed by both NMR and affinity binding experiments, are found to be important in vivo. These findings are the first demonstration of how the novel structure of the knotted tudor domain impacts on RNA binding and how this influences in vivo function.

The zinc finger domain in the large subunit of TFIIE (TFIIEalpha) is phylogenetically conserved and is essential for transcription. Here, we determined the solution structure of this domain by using NMR. It consisted of one alpha-helix and five beta-strands, showing novel features distinct from previously determined zinc-binding structures. We created point mutants of TFIIEalpha in this domain and examined their binding abilities to other general transcription factors as well as their transcription activities. Four Zn(2+)-ligand mutants, in which each of cysteine residues at positions 129, 132, 154, and 157 was replaced by alanine, possessed no transcription activities on a linearized template, whereas, on a supercoiled template, interesting functional asymmetry was observed: although the C-terminal two mutants abolished transcription activity (5%), the N-terminal two mutants retained about 20% activities. The N-terminal two mutants bound stronger to the small subunit of TFIIF than the wild type and the C-terminal two mutants were impaired in their binding abilities to the XPB subunits of TFIIH. These suggest that the structural integrity of the zinc finger domain is essential for the TFIIE function, particularly in the transition from the transcription initiation to elongation and the conformational tuning of this domain for appropriate positioning of TFIIF, TFIIH, and polymerase II would be needed depending on the situation and timing.