Characterization of assembly factors for type IV secretion systems

摘要 许多细菌病原体使用复杂的、专门的分泌系统来输出毒素并将 效应器进入哺乳动物细胞的细胞质。尽管已经在以下方面做了大量的工作 确定这些分泌系统的组成，人们对这些分泌系统所需的因素知之甚少 它们的组装/功能。我们建议通过研究这些组装因素来确定和表征这些组装因素 嗜肺军团菌IVB型分泌系统。该系统称为Dot/ICM，由L. 嗜肺性肺炎在肺泡巨噬细胞内存活和复制，从而介导肺炎样 一种叫做退伍军人症的疾病。嗜肺性乳杆菌T4BSS由大约30个 Dot/ICM基因。这些基因对这种病原体的细胞内复制和毒力是必不可少的，但 大多数都不是有机体在培养基上生长所必需的。然而，dotL在ALL中是一个必不可少的基因 可以分离出允许∆dotL菌株存活的条件和大量抑制子。这些 抑制物包括其他DOT/ICM基因和一些可能的组装因子的突变 包括DjlA和LdsA。基于这些观察，我们建议分离额外的∆点突变致死性 使用TN-seq的抑制子，并阐明DjlA和LdsA如何在装配/功能中发挥作用 DOT/ICM T4BSS。获得的信息将为了解嗜肺乳杆菌T4BSS是如何组装的提供洞察力 和功能，并可能揭示药物干预的新靶点。

Abstract Many bacterial pathogens employ complex, specialized secretion systems to export toxins and deliver effectors into the cytoplasm of mammalian cells. Although a significant amount of work has been done on identifying components of these secretion systems, less is known about the factors that are required for their assembly/function. We propose to identify and characterize these assembly factors by studying the type IVB secretion system of Legionella pneumophila. This system, called Dot/Icm, is used by L. pneumophila to survive and replicate within alveoloar macrophages, thereby mediating a pneumonia-like disease called Legionnaires’ disease. The L. pneumophila T4BSS is encoded by approximately thirty dot/icm genes. These genes are essential for intracellular replication and virulence of this pathogen, but most are not required for growth of the organism on media. However, dotL is an essential gene under all conditions and a large number of suppressors can be isolated that allow a ∆dotL strain to live. These suppressors include mutations in other dot/icm genes and in a number of putative assembly factors including DjlA and LdsA. Based on these observations, we propose to isolate additional ∆dotL lethality suppressors using Tn-seq and to elucidate how DjlA and LdsA function in the assembly/function of the Dot/Icm T4BSS. Information acquired will provide insight into how L. pneumophila’s T4BSS assembles and functions and may reveal novel targets for drug intervention.