Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA.
J Mol Biol. 2010 Nov 19;404(1):1-15. doi: 10.1016/j.jmb.2010.09.040. Epub 2010 Sep 25.
Spn1/Iws1 plays essential roles in the regulation of gene expression by RNA polymerase II (RNAPII), and it is highly conserved in organisms ranging from yeast to humans. Spn1 physically and/or genetically interacts with RNAPII, TBP (TATA-binding protein), TFIIS (transcription factor IIS), and a number of chromatin remodeling factors (Swi/Snf and Spt6). The central domain of Spn1 (residues 141-305 out of 410) is necessary and sufficient for performing the essential functions of SPN1 in yeast cells. Here, we report the high-resolution (1.85 Å) crystal structure of the conserved central domain of Saccharomyces cerevisiae Spn1. The central domain is composed of eight α-helices in a right-handed superhelical arrangement and exhibits structural similarity to domain I of TFIIS. A unique structural feature of Spn1 is a highly conserved loop, which defines one side of a pronounced cavity. The loop and the other residues forming the cavity are highly conserved at the amino acid level among all Spn1 family members, suggesting that this is a signature motif for Spn1 orthologs. The locations and the molecular characterization of temperature-sensitive mutations in Spn1 indicate that the cavity is a key attribute of Spn1 that is critical for its regulatory functions during RNAPII-mediated transcriptional activity.
Spn1/Iws1 在 RNA 聚合酶 II（RNAPII）调控基因表达中发挥重要作用，在从酵母到人等生物中高度保守。Spn1 与 RNAPII、TBP（TATA 结合蛋白）、TFIIS（转录因子 IIS）和许多染色质重塑因子（Swi/Snf 和 Spt6）发生物理和/或遗传相互作用。Spn1 的中心结构域（410 个残基中的 141-305 位）对于酵母细胞中 SPN1 的基本功能是必需且充分的。在这里，我们报道了酿酒酵母 Spn1 的保守中心结构域的高分辨率（1.85Å）晶体结构。该中心结构域由右手超螺旋排列的八个α-螺旋组成，与 TFIIS 的结构域 I 具有结构相似性。Spn1 的一个独特结构特征是一个高度保守的环，定义了一个明显空腔的一侧。该环和形成空腔的其他残基在所有 Spn1 家族成员的氨基酸水平上高度保守，表明这是 Spn1 同源物的特征基序。Spn1 中温度敏感突变的位置和分子特征表明，该空腔是 Spn1 的关键属性，对于其在 RNAPII 介导的转录活性期间的调节功能至关重要。
