Mitsiou D J, Stunnenberg H G
Department of Molecular Biology, University of Nijmegen, The Netherlands.
Mol Cell. 2000 Sep;6(3):527-37. doi: 10.1016/s1097-2765(00)00052-6.
Transcription of TATA box-containing genes by RNA polymerase II is mediated by TBP-containing and TBP-free multisubunit complexes consisting of common and unique components. We have identified a highly stable TBP-TFIIA-containing complex, TAC, which is detectable in embryonal carcinoma (EC) cells but not in differentiated cells. TAC contains the TFIIAgamma subunit and the unprocessed form of TFIIAalphabeta, although the processed TFIIAalpha and TFIIAbeta subunits are present in EC cells. TAC mediates transcriptional activation by RNA polymerase II in vivo, even though it does not contain classical TAFs. Formaldehyde cross-linking revealed that in EC but not in differentiated cells, association of TBP with chromatin is strongly enhanced when complexed with TFIIA in vivo. Remarkably, the TFIIAalphabeta precursor is preferentially, if not exclusively, associated with chromatin as compared to the processed subunits present in "free" TFIIA in EC cells.
含TATA框基因的转录由RNA聚合酶II介导，该过程由含TBP和不含TBP的多亚基复合物介导，这些复合物由共同和独特的成分组成。我们鉴定出一种高度稳定的含TBP-TFIIA复合物，即TAC，它在胚胎癌细胞（EC）中可检测到，但在分化细胞中则检测不到。TAC包含TFIIAgamma亚基和未加工形式的TFIIAalphabeta，尽管加工后的TFIIAalpha和TFIIAbeta亚基存在于EC细胞中。TAC在体内介导RNA聚合酶II的转录激活，尽管它不包含经典的TAF。甲醛交联显示，在EC细胞而非分化细胞中，体内与TFIIA复合时，TBP与染色质的结合会强烈增强。值得注意的是，与EC细胞中“游离”TFIIA中存在的加工后亚基相比，TFIIAalphabeta前体优先（如果不是唯一的话）与染色质相关联。
