Macromolecular Structure Laboratory, The Francis Crick Institute, London, UK.
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Nat Commun. 2021 Sep 22;12(1):5590. doi: 10.1038/s41467-021-25849-0.
Excessive replication of Saccharomyces cerevisiae Ty1 retrotransposons is regulated by Copy Number Control, a process requiring the p22/p18 protein produced from a sub-genomic transcript initiated within Ty1 GAG. In retrotransposition, Gag performs the capsid functions required for replication and re-integration. To minimize genomic damage, p22/p18 interrupts virus-like particle function by interaction with Gag. Here, we present structural, biophysical and genetic analyses of p18m, a minimal fragment of Gag that restricts transposition. The 2.8 Å crystal structure of p18m reveals an all α-helical protein related to mammalian and insect ARC proteins. p18m retains the capacity to dimerise in solution and the crystal structures reveal two exclusive dimer interfaces. We probe our findings through biophysical analysis of interface mutants as well as Ty1 transposition and p18m restriction in vivo. Our data provide insight into Ty1 Gag structure and suggest how p22/p18 might function in restriction through a blocking-of-assembly mechanism.
酿酒酵母 Ty1 反转录转座子的过度复制受拷贝数控制调节，该过程需要从 Ty1 GAG 内起始的亚基因组转录物产生的 p22/p18 蛋白。在反转录转座过程中，Gag 执行复制和重新整合所需的衣壳功能。为了最小化基因组损伤，p22/p18 通过与 Gag 的相互作用中断病毒样颗粒功能。在这里，我们介绍了 p18m 的结构、生物物理和遗传分析，p18m 是一种限制转座的 Gag 的最小片段。p18m 的 2.8Å 晶体结构揭示了一种与哺乳动物和昆虫 ARC 蛋白相关的全α-螺旋蛋白。p18m 在溶液中保留二聚化的能力，晶体结构揭示了两个独特的二聚体界面。我们通过对界面突变体以及 Ty1 转座和体内 p18m 限制的生物物理分析来探测我们的发现。我们的数据提供了对 Ty1 Gag 结构的深入了解，并表明 p22/p18 如何通过组装阻断机制在限制中发挥作用。
