Ebola virus (EBOV) is an enveloped negative-sense RNA virus and a member of the filovirus family. Nucleoprotein (NP) expression alone leads to the formation of inclusion bodies (IBs), which are critical for viral RNA synthesis. The matrix protein, VP40, not only plays a critical role in virus assembly/budding, but also can regulate transcription and replication of the viral genome. However, the molecular mechanism by which VP40 regulates viral RNA synthesis and virion assembly/budding is unknown. Here, we show that within IBs the N-terminus of NP recruits VP40 and is required for VLP-containing NP release. Furthermore, we find four point mutations (L692A, P697A, P698A and W699A) within the C-terminal hydrophobic core of NP result in a stronger VP40-NP interaction within IBs, sequestering VP40 within IBs, reducing VP40-VLP egress, abolishing the incorporation of NC-like structures into VP40-VLP, and inhibiting viral RNA synthesis, suggesting that the interaction of N-terminus of NP with VP40 induces a conformational change in the C-terminus of NP. Consequently, the C-terminal hydrophobic core of NP is exposed and binds VP40, thereby inhibiting RNA synthesis and initiating virion assembly/budding.

中文翻译：

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埃博拉病毒 VP40 与核蛋白的两阶段相互作用导致从病毒 RNA 合成转变为病毒粒子组装/出芽

埃博拉病毒 (EBOV) 是一种有包膜的负义 RNA 病毒，是丝状病毒家族的成员。仅核蛋白 (NP) 表达会导致包涵体 (IB) 的形成，这对病毒 RNA 合成至关重要。基质蛋白VP40不仅在病毒组装/出芽中起关键作用，还可以调节病毒基因组的转录和复制。然而，VP40调节病毒RNA合成和病毒粒子组装/出芽的分子机制尚不清楚。在这里，我们表明在 IBs 中，NP 的 N 端招募 VP40，并且是包含 VLP 的 NP 释放所必需的。此外，我们发现 NP 的 C 末端疏水核心内的四个点突变（L692A、P697A、P698A 和 W699A）导致 IBs 内的 VP40-NP 相互作用更强，将 VP40 隔离在 IBs 内，减少 VP40-VLP 出口，消除了在VP40-VLP中掺入NC样结构，并抑制病毒RNA合成，表明NP的N末端与VP40的相互作用诱导了NP C末端的构象变化。因此，NP 的 C 末端疏水核心被暴露并与 VP40 结合，从而抑制 RNA 合成并启动病毒粒子组装/出芽。