African swine fever virus (ASFV), which poses significant risks to the global economy, encodes a unique host-independent transcription system. This system comprises an eight-subunit RNA polymerase (vRNAP), temporally expressed transcription factors and transcript associated proteins, facilitating cross-species transmission via intermediate host. The protein composition of the virion and the presence of transcription factors in virus genome suggest existence of distinct transcription systems during viral infection. However, the precise mechanisms of transcription regulation remain elusive. Through analyses of dynamic transcriptome, vRNAP-associated components and cell-based assay, the critical role of M1249L in viral transcription regulation has been highlighted. Atomic-resolution structures of vRNAP-M1249L supercomplex, exhibiting a variety of conformations, have uncovered the dual functions of M1249L. During early transcription, M1249L could serve as multiple temporary transcription factors with C-terminal domain acting as a switcher for activation/inactivation, while during late transcription it aids in the packaging of the transcription machinery. The structural and functional characteristics of M1249L underscore its vital roles in ASFV transcription, packaging, and capsid assembly, presenting novel opportunities for therapeutic intervention.

非洲猪瘟病毒 （ASFV） 对全球经济构成重大风险，它编码了一种独特的不依赖宿主的转录系统。该系统包括一个 8 个亚基的 RNA 聚合酶 （vRNAP）、时间表达的转录因子和转录本相关蛋白，促进通过中间宿主的跨物种传递。病毒粒子的蛋白质组成和病毒基因组中转录因子的存在表明在病毒感染过程中存在不同的转录系统。然而，转录调控的确切机制仍然难以捉摸。通过对动态转录组、vRNAP 相关成分和基于细胞的分析，强调了 M1249L 在病毒转录调控中的关键作用。vRNAP-M1249L 超复合物的原子级结构表现出多种构象，揭示了 M1249L 的双重功能。在早期转录期间，M1249L 可以作为多个临时转录因子，C 端结构域充当激活/失活的切换器，而在晚期转录期间，它有助于转录机制的包装。M1249L 的结构和功能特征强调了其在 ASFV 转录、包装和衣壳组装中的重要作用，为治疗干预提供了新的机会。