非洲猪瘟病毒 I73R 蛋白是介导 Z 结合依赖与非依赖生物学功能的多功能 Zα 结构域
The African swine fever virus I73R protein is a multifunctional Zα domain that mediates both Z-binding-dependent and -independent biological functions through induction of phase separation
非洲猪瘟病毒（ASFV）I73R 编码的蛋白仅由一个 Zα 结构域组成，研究证实其同时具备 Z 结合、B-to-Z 转换和诱导液-液相分离（LLPS）三种活性，且 B-to-Z 转换能力优于人 ADAR1 Zα，Z 结合位点 Y48I 突变后仍保留转换活性。在 ASFV 感染细胞中，I73R 与 dsRNA、Z-DNA 和 Z-RNA 形成胞质凝聚体；异位表达天然型或 Z 结合缺陷型 I73R 均能相似程度地抑制亚砷酸盐诱导的应激颗粒，且均不定位于这些细胞器。
来源：Nucleic Acids Research · doi.org
African swine fever virus (ASFV) I73R encodes a protein consisting only of a Zalpha (Zα) domain. Here, we studied its biochemical properties. Complementary approaches demonstrated that I73R is a multifunctional Zα domain that combines Z-binding, B-to-Z conversion, and liquid–liquid phase separation (LLPS) induction activities. I73R proved to be a better converter than human ADAR1 Zα, and it retained conversion activity with Y48I mutation of its Z-binding site. Next, we investigated I73R biological functions, leading to the following findings: (i) Ectopic expression of I73R or mutated I73R with deficient Z-binding both inhibited arsenite-induced stress granules to a similar extent, and none of these proteins localized within these organelles. (ii) I73R formed cytosolic condensates with dsRNA, Z-DNA, and Z-RNA in ASFV-infected cells. (iii) Rescuing of ASFV I73R deletion by sequences encoding natural, mutated, and chimeric forms of Zα domains demonstrated that I73R mediated both Z-binding-dependent and -independent biological functions through induction of LLPS. This conclusion was further supported by the effect of the LLPS inhibitor 1,6-hexanediol on the replication of ASFV I73R recombinant strains. This study further demonstrates the functional diversity that exists among Zα domains. It unravels new outlooks targeting Zα domain-mediated LLPS for the development of pharmaceutical molecules able to regulate viral and cellular Zα domain-containing proteins.