Domain architectures of the Scm3p protein provide insights into centromere function and evolution
Domain architectures of the Scm3p protein provide insights into centromere function and evolution
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DOI：
10.4161/cc.6.20.4793
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发表时间：
2007-10-15
期刊：
影响因子：
4.3
通讯作者：
Wu, Carl
中科院分区：
文献类型：
--
作者：
Aravind, L.;Iyer, Lakshminarayan M.;Wu, Carl
最近，Scm 3 p已被证明是着丝粒染色质的非组蛋白组分，其与CenH 3-H4组蛋白化学计量结合，并且是酿酒酵母中着丝粒组装所需的。Scm 3 p在真菌中是保守的，并且在蛋白质大小上显示出显着的变化，范围从S.与粗糙脉孢菌中的1300个氨基酸相似。这主要是由于可变的C-末端区段与保守的N-末端CenH 3相互作用结构域连接。我们已经发现，Scm 3 p的扩展的C-末端区域的显著特征是由单个或多个预测的DNA结合结构域的不同版本的MYB和C2 H2锌指结构域，AT-钩，和一个新的富含半胱氨酸的金属螯合簇的谱系特异性融合，这些都是Scm 3的小版本所不存在的。相反，S.酿酒酵母点着丝粒被CBF 3 DNA结合复合物的组分识别，CBF 3 DNA结合复合物在芽殖酵母的近亲中是保守的，但相应地在具有区域着丝粒的更远的真菌中不存在。因此，在大的Scm 3 p蛋白中发现的C-末端DNA结合基序可能与CenH 3一起沿着，通过识别和容纳进化过程中的着丝粒DNA的谱系特异性多样性而作为关键的表观遗传信号。
Recently, Scm3p has been shown to be a nonhistone component of centromeric chromatin that binds stoichiometrically to CenH3-H4 histones, and to be required for the assembly of kinetochores in Saccharomyces cerevisiae. Scm3p is conserved across fungi, and displays a remarkable variation in protein size, ranging from similar to 200 amino acids in S. cerevisiae to similar to 1300 amino acids in Neurospora crassa. This is primarily due a variable C-terminal segment that is linked to a conserved N-terminal, CenH3-interacting domain. We have discovered that the extended C-terminal region of Scm3p is strikingly characterized by lineage-specific fusions of single or multiple predicted DNA-binding domains different versions of the MYB and C2H2 zinc finger domains, AT-hooks, and a novel cysteine-rich metal-chelating cluster that are absent from the small versions of Scm3. Instead, S. cerevisiae point centromeres are recognized by components of the CBF3 DNA binding complex, which are conserved amongst close relatives of budding yeast, but are correspondingly absent from more distant fungi that possess regional centromeres. Hence, the C-terminal DNA binding motifs found in large Scm3p proteins may, along with CenH3, serve as a key epigenetic signal by recognizing and accommodating the lineage-specific diversity of centromere DNA in course of evolution.