SFPQ / PSPC1异源二聚体的晶体结构为人类DBHS家族蛋白的优先异源二聚化提供了见识。,Journal of Biological Chemistry

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SFPQ / PSPC1异源二聚体的晶体结构为人类DBHS家族蛋白的优先异源二聚化提供了见识。
Journal of Biological Chemistry ( IF 4.0 ) Pub Date : 2018-03-14 , DOI: 10.1074/jbc.ra117.001451
Jie Huang ₁ , G Patricia Casas Garcia ₁ , Matthew A Perugini ₁ , Archa H Fox ₂ , Charles S Bond ₃ , Mihwa Lee ₄

Affiliation

果蝇行为人类剪接（DBHS）蛋白家族的成员是涉及许多核功能层的核蛋白，包括RNA生物发生以及DNA修复。保守的DBHS域是DBHS蛋白质家族的定义，它提供了一个二聚化平台，对于这些蛋白质的结构完整性和功能至关重要。三种人类DBHS蛋白，即富含剪接因子脯氨酸和谷氨酰胺（SFPQ），散斑成分1（PSPC1）和不包含POU域的八聚体结合蛋白（NONO），形成同二聚体或异源二聚体。然而，优先异二聚化的相对亲和力和机理细节尚待破译。在这里，我们将SFPQ / PSPC1异二聚体的晶体结构报告为2。分辨率为3-Å，并分析了SFPQ / PSPC1异二聚体与先前表征的SFPQ同二聚体之间的细微结构差异。分析超速离心法估计包含SFPQ的二聚体的二聚化平衡表明，包含SFPQ的二聚体在低微摩尔浓度下会解离，并且异二聚体的亲和力高于同二聚体。此外，我们观察到SFPQ / PSPC1异二聚体的表观解离常数比SFPQ / NONO异二聚体的表观解离常数低6倍以上。我们建议这些二聚体亲和力的差异可能代表了一种潜在的机制，通过该机制，较低的相对细胞丰度的PSPC1可以与NONO竞争，从而与SFPQ异源二聚化。分析超速离心法估计包含SFPQ的二聚体的二聚化平衡表明，包含SFPQ的二聚体在低微摩尔浓度下会解离，并且异二聚体的亲和力高于同二聚体。此外，我们观察到SFPQ / PSPC1异二聚体的表观解离常数比SFPQ / NONO异二聚体的表观解离常数低6倍以上。我们建议这些二聚体亲和力的差异可能代表了一种潜在的机制，通过该机制，较低的相对细胞丰度的PSPC1可以与NONO竞争以与SFPQ异源二聚化。分析超速离心法估计包含SFPQ的二聚体的二聚化平衡表明，包含SFPQ的二聚体在低微摩尔浓度下会解离，并且异二聚体的亲和力高于同二聚体。此外，我们观察到SFPQ / PSPC1异二聚体的表观解离常数比SFPQ / NONO异二聚体的表观解离常数低6倍以上。我们建议这些二聚体亲和力的差异可能代表了一种潜在的机制，通过该机制，较低的相对细胞丰度的PSPC1可以与NONO竞争以与SFPQ异源二聚化。我们观察到，SFPQ / PSPC1异二聚体的表观解离常数比SFPQ / NONO异二聚体的表观解离常数低6倍以上。我们建议这些二聚体亲和力的差异可能代表了一种潜在的机制，通过该机制，较低的相对细胞丰度的PSPC1可以与NONO竞争以与SFPQ异源二聚化。我们观察到，SFPQ / PSPC1异二聚体的表观解离常数比SFPQ / NONO异二聚体的表观解离常数低6倍以上。我们建议这些二聚体亲和力的差异可能代表了一种潜在的机制，通过该机制，较低的相对细胞丰度的PSPC1可以与NONO竞争，从而与SFPQ异源二聚化。

"点击查看英文标题和摘要"

Crystal structure of a SFPQ/PSPC1 heterodimer provides insights into preferential heterodimerization of human DBHS family proteins.

Members of the Drosophila behavior human splicing (DBHS) protein family are nuclear proteins implicated in many layers of nuclear functions, including RNA biogenesis as well as DNA repair. Definitive of the DBHS protein family, the conserved DBHS domain provides a dimerization platform that is critical for the structural integrity and function of these proteins. The three human DBHS proteins, splicing factor proline- and glutamine-rich (SFPQ), paraspeckle component 1 (PSPC1), and non-POU domain-containing octamer-binding protein (NONO), form either homo- or heterodimers; however, the relative affinity and mechanistic details of preferential heterodimerization are yet to be deciphered. Here we report the crystal structure of a SFPQ/PSPC1 heterodimer to 2.3-Å resolution and analyzed the subtle structural differences between the SFPQ/PSPC1 heterodimer and the previously characterized SFPQ homodimer. Analytical ultracentrifugation to estimate the dimerization equilibrium of the SFPQ-containing dimers revealed that the SFPQ-containing dimers dissociate at low micromolar concentrations and that the heterodimers have higher affinities than the homodimer. Moreover, we observed that the apparent dissociation constant for the SFPQ/PSPC1 heterodimer was over 6-fold lower than that of the SFPQ/NONO heterodimer. We propose that these differences in dimerization affinity may represent a potential mechanism by which PSPC1 at a lower relative cellular abundance can outcompete NONO to heterodimerize with SFPQ.

更新日期：2019-11-01

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