P53 and TFIIEα share a common binding site on the Tfb1/p62 subunit of TFIIH

The general transcription factor IN is recruited to the transcription preinitiation complex through an interaction between its p62/Tfb1 subunit and the a-subunit of the general transcription factor HE (TFIIE alpha). We have determined that the acidic carboxyl terminus of TFIIEa (TFIIE alpha(336-439)) directly binds the amino-terminal PH domain of p62/Tfb1 with nanomolar affinity. NMR mapping and mutagenesis studies demonstrate that the TFIIEa binding site on p62/Tfb1 is identical to the binding site for the second transactivation domain of p53 (p53 TAD2). In addition, we demonstrate that TFIIE alpha(336-439) is capable of competing with p53 for a common binding site on p62/ Tfb1 and that TFIIE alpha(336-439) and the diphosphorylated form (pS46/ pT55) of p53 TAD2 have similar binding constants. NMR structural studies reveal that TFIIE alpha(336-439) contains a small domain (residues 395-433) folded in a novel beta beta alpha alpha alpha topology. NMR mapping studies demonstrate that two unstructured regions (residues 377-393 and residues 433-439) located on either side of the folded domain appear to be required for TFIIE alpha(336-439) binding to p62/Tfb1 and that these two unstructured regions are held close to each other in three-dimensional space by the novel structured domain. We also demonstrate that, like p53, TFIIE alpha(336-439) can activate transcription in vivo. These results point to an important interplay between the general transcription factor TFIIEa and the tumor suppressor protein p53 in regulating transcriptional activation that may be modulated by the phosphorylation status of p53.