Vary Jay C, Gangaraju Vamsi K, Qin Jun, Landel Carolyn Church, Kooperberg Charles, Bartholomew Blaine, Tsukiyama Toshio
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
Mol Cell Biol. 2003 Jan;23(1):80-91. doi: 10.1128/MCB.23.1.80-91.2003.
There are several classes of ATP-dependent chromatin remodeling complexes, which modulate the structure of chromatin to regulate a variety of cellular processes. The budding yeast, Saccharomyces cerevisiae, encodes two ATPases of the ISWI class, Isw1p and Isw2p. Previously Isw1p was shown to copurify with three other proteins. Here we identify these associated proteins and show that Isw1p forms two separable complexes in vivo (designated Isw1a and Isw1b). Biochemical assays revealed that while both have equivalent nucleosome-stimulated ATPase activities, Isw1a and Isw1b differ in their abilities to bind to DNA and nucleosomal substrates, which possibly accounts for differences in specific activities in nucleosomal spacing and sliding. In vivo, the two Isw1 complexes have overlapping functions in transcriptional regulation of some genes yet distinct functions at others. In addition, these complexes show different contributions to cell growth at elevated temperatures.
存在几类依赖ATP的染色质重塑复合体，它们可调节染色质结构以调控多种细胞过程。芽殖酵母酿酒酵母编码两种ISWI类的ATP酶，即Isw1p和Isw2p。此前研究表明Isw1p可与其他三种蛋白质共同纯化。在此我们鉴定出这些相关蛋白，并表明Isw1p在体内形成两种可分离的复合体（命名为Isw1a和Isw1b）。生化分析显示，虽然二者都具有等效的核小体刺激的ATP酶活性，但Isw1a和Isw1b在结合DNA和核小体底物的能力上存在差异，这可能解释了它们在核小体间距和滑动方面的比活性差异。在体内，这两种Isw1复合体在某些基因的转录调控中具有重叠功能，但在其他基因上具有不同功能。此外，这些复合体在高温下对细胞生长的贡献也不同。
