This study characterizes how the host protein acidic nuclear phosphoprotein 32 (ANP32) participates in formation of the Tilapia Lake Virus (TiLV) replication complex. TiLV is a segmented, negative-strand RNA virus in the Amnoonviridae family within the Articulavirales order. The work addresses whether the ANP32 dependency observed for influenza virus replication is conserved in a phylogenetically distant member of the same order.
Using purified components and reconstitution, the authors directly investigated complexes formed between the TiLV RNA-dependent RNA polymerase (TiLV-Pol) and either tilapia (tiANP32) or human (huANP32A) ANP32A. The structural and biochemical data demonstrate that ANP32 acts as a scaffold that stabilizes distinct polymerase conformations and coordinates assembly of an asymmetric polymerase dimer with roles in replication and encapsidation.
The authors combined in vitro reconstitution with biophysical and biochemical analyses and determined high-resolution structures by single-particle cryo-electron microscopy. These complementary methods allowed visualization of the TiLV-Pol–ANP32 assemblies, identification of domain interactions, and correlation of structural arrangements with inferred functional states (encapsidase versus replicase conformations). The source reports these approaches but does not provide methodological parameter values in the summary.
The tilapia ANP32 leucine-rich repeat domain functions as a scaffold that stabilizes apo-TiLV-Pol in an encapsidase conformation. The tiANP32–encapsidase complex can recruit and stabilize a second TiLV-Pol in a replicase conformation, producing an asymmetric TiLV-Pol dimer bridged by ANP32.
Despite TiLV-Pol being approximately 40% smaller than orthomyxovirus polymerases, the ANP32-stabilized asymmetric dimer architecture is described as remarkably similar to known orthomyxovirus replication complexes. This structural resemblance suggests that the basic organized arrangement of an encapsidase bound to ANP32 plus a replicase partner is a conserved solution for genome replication within the order.
Beyond polymerase scaffolding, the ANP32 low-complexity acidic region was found to interact with the TiLV nucleoprotein. This interaction is consistent with a conserved role for ANP32 in coordinating ribonucleoprotein (RNP) assembly during viral genome replication and encapsidation. The source frames this interaction as supportive evidence that ANP32 couples polymerase assembly to nucleoprotein engagement, although details of binding interfaces and affinities are not provided in the summary.
Taken together, the structural, biochemical and reconstitution data support the conclusion that ANP32 is an ancient and likely broadly conserved host factor required for genome replication and encapsidation across the Articulavirales order. The similarity of the TiLV complex architecture to orthomyxovirus replication complexes, despite substantial polymerase size differences, underlines a shared mechanistic basis for host-assisted replication among these diverse viruses.
TiLV is noted as an emerging fish pathogen that causes high mortality in tilapia aquaculture. The authors state that their findings provide insight into tilapia ANP32 modifications that could be used to engineer TiLV-resistant tilapia. The summary does not enumerate specific genetic changes, experimental validation of resistance, or translational pathways; it only reports that the structural information identifies candidate regions of ANP32 for consideration in resistance engineering.
All statements above are derived from the article summary and abstract. The summary describes experimental approaches (in vitro reconstitution, biophysical and biochemical analyses, cryo-EM) and the principal structural and interaction findings but does not include detailed experimental parameters, numerical metrics, or specific mutation studies. Where the source did not report particulars, those details are not included here.
The reported structures and interaction data establish that ANP32 scaffolds TiLV polymerase and engages nucleoprotein, assembling an asymmetric polymerase dimer with encapsidase and replicase roles. These findings indicate a conserved requirement for ANP32 across the Articulavirales order and highlight potential targets within tilapia ANP32 for engineering approaches aimed at reducing TiLV susceptibility in aquaculture species.