Functional characterization of the interacting domains of the positive coactivator PC4 with the transcription factor AP-2α
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- 作者：Zhong ; Li ; Wang ; Yingqun ; Kannan ; Perry ; Tainsky ; Michael A.
- 关键词：AP-2 ; Transcription self-interference ; Transcriptional cofactors ; AD ; activation domain ; CTD ; C-terminal domain ; CAT ; chloramphenicol acetyl transferase ; GST ; glutathione S-transferase ; TNT ; transcription/translation systems
- 刊名：Gene
- 出版年：2003
- 出版时间：November 27, 2003
- 年：2003
- 卷：320
- 期：Complete
- 页码：155-164
- 全文大小：620 K
文摘
The transcriptional positive cofactor 4 (PC4) physically interacts with the transcription factor, activator protein-2 (AP-2) α, and overexpression of PC4 results in a relief of the AP-2 transcriptional self-interference, which is induced by high levels of AP-2α expression. PC4 was initially described as a DNA-binding protein that enhances the activator-dependent transcription of class II genes in vitro, but it was later shown that PC4 could also act as a potent repressor of transcription on specific DNA structures such as single-stranded (ss) DNA, DNA ends and heteroduplex DNA. To further explore the functional domains of PC4 and its ssDNA-binding effect in the interaction with AP-2α and on AP-2 transcriptional activity, we investigated the C-terminal domain of PC4 (PC4-CTD) and several PC4 mutants in which the ssDNA binding function was interrupted. We found that the C-terminal domain of PC4 physically interacts with AP-2α and retains the function of full-length protein in relieving transcription self-interference of AP-2. A point-mutated form of PC4 within the C-terminal domain β-ridge, PC4 W89A, or a triple mutant in the β2–β3 loop of PC4, F77A/K78G/K80G, inactivate the ability of PC4 to bind AP-2α and to relieve the transcription self-interference of AP-2α. In addition, point-mutated forms of AP-2α within the activation domain (AD) that inactivate AP-2 transcription activity also lose their self-interference function. Our data suggest that the C-terminal domain of the transcription cofactor PC4 is critical for AP-2α transcriptional interference that is mediated by the activation domain of AP-2α.