Hyperparasitism is a common pattern in nature that is not limited to cellular organisms. Giant viruses infecting protists can be hyperparasitized by smaller ones named virophages. In addition, both may carry episomal DNA molecules known as transpovirons in their particles. They all share transcriptional regulatory elements that dictate the expression of their genes within viral factories built by giant viruses in the host cytoplasm. This suggests the existence of interactions between their respective transcriptional networks. Here we investigated Acanthamoeba castellanii cells infected by a giant virus (megavirus chilensis), and coinfected with a virophage (zamilon vitis) and/or a transpoviron (megavirus vitis transpoviron). Infectious cycles were monitored through time-course RNA sequencing to decipher the transcriptional program of each partner and its impact on the gene expression of the others. We found highly diverse transcriptional responses. While the giant virus drastically reshaped the host cell transcriptome, the transpoviron had no effect on the gene expression of any of the players. In contrast, the virophage strongly modified the giant virus gene expression, albeit transiently, without altering the protein composition of mature viral particles. The virophage also induced the overexpression of transpoviron genes, likely through the indirect upregulation of giant virus-encoded transcription factors. Together, these analyses document the intricated transcriptionally regulated networks taking place in the infected cell.

过度寄生是自然界中的常见模式，不仅限于细胞生物。感染原生生物的巨型病毒可以被称为病毒噬菌体的较小病毒过度寄生。此外，两者的颗粒中都可能携带称为 transpovirons 的游离型 DNA 分子。它们都共享转录调控元件，这些元件决定了其基因在宿主细胞质中由巨型病毒构建的病毒工厂中的表达。这表明它们各自的转录网络之间存在相互作用。在这里，我们研究了被巨型病毒 （巨病毒 chilensis） 感染并共同感染病毒噬菌体 （zamilon vitis） 和/或转波维隆 （megavirus vitis transpoviron） 的棘阿米巴细胞。通过时程 RNA 测序监测感染周期，以破译每个伴侣的转录程序及其对其他伴侣基因表达的影响。我们发现了高度多样化的转录反应。虽然巨型病毒彻底重塑了宿主细胞转录组，但 transpoviron 对任何参与者的基因表达都没有影响。相比之下，病毒噬菌体强烈修饰了巨病毒基因的表达，尽管是短暂的，而不会改变成熟病毒颗粒的蛋白质组成。病毒噬菌体还诱导了 transpoviron 基因的过表达，可能是通过间接上调巨型病毒编码的转录因子。总之，这些分析记录了受感染细胞中发生的错综复杂的转录调控网络。