Minimum essential region of CCG1/TAF_II250 required for complementing the temperature-sensitive cell cycle mutants, tsBN462 and ts13 cells, of hamster BHK21 cells

CCG1/TAF_II250, the largest subunit of theTFIID complex, is mutated in ts cell cycle mutants of BHK21 cells, ts13 and tsBN462, which have a promoter-selective transcriptional defect. A series of deletion mutants of CCG1 cDNA were prepared and transfected into these mutants, in order to identify functional domains of CCG1 required for the complementation of ts 13/BN462 mutation. We determined the minimum size of CCG1: CCG1ME, essential for complementing the ts mutation, which possessed one proline cluster, an HMG1-like domain, and a nuclear localization signal, but which lacked the bromo domains and the acidic phosphorylation sites for casein kinase II common to transcriptional activators. It encodes a protein of 140 kDa. These characteristics of CCG1ME correspond to yeast TAF_II145, the yeast homolog of human TAF_II250. CCG1ME bound to TBP, creating its own TFIID complex different from that of the endogenous mutated CCG1 in ts⁺ transformants of tsBN462 cells.