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STN1–POLA2 interaction provides a basis for primase-pol α stimulation by human STN1
Nucleic Acids Research ( IF 14.9 ) Pub Date : 2017-07-19 , DOI: 10.1093/nar/gkx621
Swapna Ganduri , Neal F. Lue

The CST (CTC1–STN1–TEN1) complex mediates critical functions in maintaining telomere DNA and overcoming genome-wide replication stress. A conserved biochemical function of the CST complex is its primase-Pol α (PP) stimulatory activity. In this report, we demonstrate the ability of purified human STN1 alone to promote PP activity in vitro. We show that this regulation is mediated primarily by the N-terminal OB fold of STN1, but does not require the DNA-binding activity of this domain. Rather, we observed a strong correlation between the PP-stimulatory activity of STN1 variants and their abilities to bind POLA2. Remarkably, the main binding target of STN1 in POLA2 is the latter's central OB fold domain. In the substrate-free structure of PP, this domain is positioned so as to block nucleic acid entry to the Pol α active site. Thus the STN1–POLA2 interaction may promote the necessary conformational change for nucleic acid delivery to Pol α and subsequent DNA synthesis. A disease-causing mutation in human STN1 engenders a selective defect in POLA2-binding and PP stimulation, indicating that these activities are critical for the in vivo function of STN1. Our findings have implications for the molecular mechanisms of PP, STN1 and STN1-related molecular pathology.

中文翻译:

STN1-POLA2相互作用为人类STN1刺激primase-polα提供了基础

CST(CTC1-STN1-TEN1)复合物在维持端粒DNA和克服全基因组复制压力方面起着关键作用。CST复合物的保守生化功能是其primase-Polα(PP)的刺激活性。在本报告中,我们证明了单独纯化的人STN1能够在体外促进PP活性的能力。我们表明,这种调节主要是由STN1的N端OB折叠介导的,但不需要该域的DNA结合活性。相反,我们观察到STN1变体的PP刺激活性与其结合POLA2的能力之间存在很强的相关性。值得注意的是,POLA2中STN1的主要结合靶标是后者的中央OB折叠结构域。在PP的无底物结构中,定位此结构域以阻止核酸进入Polα活性位点。因此,STN1-POLA2相互作用可能促进核酸转移至Polα和随后的DNA合成所需的构象变化。人类STN1的致病突变导致POLA2结合和PP刺激的选择性缺陷,表明这些活性对于体内至关重要STN1的功能。我们的发现对PP,STN1和STN1相关分子病理的分子机制具有重要意义。
更新日期:2017-09-21
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