Kawase H, Okuwaki M, Miyaji M, Ohba R, Handa H, Ishimi Y, Fujii-Nakata T, Kikuchi A, Nagata K
Department of Biomolecular Engineering, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
Genes Cells. 1996 Dec;1(12):1045-56. doi: 10.1046/j.1365-2443.1996.d01-223.x.
For the activation of replication and transcription from DNA in a chromatin structure, a variety of factors are thought to be needed that alter the chromatin structure. Template activating factor-I (TAF-I) has been identified as such a host factor required for replication of the adenovirus (Ad) genome complexed with viral basic core proteins (Ad core). TAF-I also stimulates transcription from the Ad core DNA.
Using mutant TAF-I proteins, we have demonstrated that the acidic stretch present in the carboxyl terminal region is essential for the stimulation of transcription from the Ad core. A genomic footprinting experiment with restriction endonuclease has revealed that TAF-I causes a structural change in the Ad core. TAF-I has been shown to have significant amino acid similarity to nucleosome assembly protein-I (NAP-I), which is involved in the formation of the chromatin structure. We have shown that TAF-I can be substituted by NAP-I in the activation of the cell-free Ad core transcription system. Two of the tripartite acidic regions and the region homologous to TAF-I in NAP-I are required for the maximal TAF-I activity of NAP-I. Furthermore, TAF-I has been shown to have NAP-I activity, and the acidic region of TAF-I is required for this activity.
Since TAF-I causes the structural change of the Ad core and thereby activates transcription, TAF-I is thought to be one of the proteins which is involved in chromatin remodeling. NAP-I is structurally related to TAF-I and functionally substitutes for TAF-I. Furthermore, TAF-I has NAP-I activity. These observations suggest that this type of molecule has dual functions, possibly by participating in facilitating the assembly of the chromatin structure as well as perturbing the chromatin structure to allow transcription to proceed.
为了激活染色质结构中DNA的复制和转录，人们认为需要多种能够改变染色质结构的因子。模板激活因子-I（TAF-I）已被确定为一种宿主因子，它是腺病毒（Ad）基因组与病毒碱性核心蛋白（Ad核心）结合进行复制所必需的。TAF-I还能刺激Ad核心DNA的转录。
通过使用突变型TAF-I蛋白，我们证明了羧基末端区域存在的酸性片段对于刺激Ad核心的转录至关重要。用限制性内切酶进行的基因组足迹实验表明，TAF-I会导致Ad核心发生结构变化。已证明TAF-I与参与染色质结构形成的核小体组装蛋白-I（NAP-I）具有显著的氨基酸相似性。我们已经表明，在无细胞Ad核心转录系统的激活过程中，TAF-I可以被NAP-I替代。NAP-I的最大TAF-I活性需要其三个酸性区域中的两个以及与TAF-I同源的区域。此外，已证明TAF-I具有NAP-I活性，并且TAF-I的酸性区域是该活性所必需的。
由于TAF-I会导致Ad核心的结构变化从而激活转录，因此TAF-I被认为是参与染色质重塑的蛋白质之一。NAP-I在结构上与TAF-I相关，并且在功能上可以替代TAF-I。此外，TAF-I具有NAP-I活性。这些观察结果表明，这类分子具有双重功能，可能是通过参与促进染色质结构的组装以及扰乱染色质结构以允许转录进行来实现的。
