Fig. 1: Human ANP32B forms a complex with monomeric H5N1 FluPolA.
a Cryo-EM map of FluPolA heterotrimer (green) and ANP32BLRR (orange). b, c Close-up views of the ANP32BLRR–PA interactions. Dashed lines indicate hydrogen bonds. The dashed rectangles in panels (a, b) denote the close-up view positions in (b, c). d Surface representation of FluPolA with the binding footprint of ANP32BLRR highlighted in orange (this study) and the RNAP II CTD serine 5 phosphorylated (S5P) peptide (PDB 6FHH). e Pull-down experiment showing Tky05 FluPolA (PB1 577E and PA 556R) binding to RNAPII S5P CTD peptide (lane 4), but not in the presence of ANP32B (lane 7). Controls include RNAP II serine 2-phosphorylated (S2P) CTD peptide (S2P), unphosphorylated peptide (unphos), scrambled peptide and no peptide. Relative FluPolA binding levels to the peptide (bottom) are shown as a percentage of S5P binding (set at 100%). Band intensity was quantitated using Image J and analysed in GraphPad Prism 10. The signal in the no peptide lane (lane 8) was set to zero and subtracted from the other lanes, essentially rendering background signal (i.e. FluPolA binding to sepharose beads in the absence of CTD peptide) zero. Data represent mean values ± standard deviation (n = 3 biologically independent experiments). Ordinary one-way ANOVA with Dunnett’s multiple comparison test was used to assess significance, with the confidence interval set at 95%. P values are as follows: S5P vs S2P: P = 0.0043; S5P vs unphos: P = 0.0007; S5P vs scrambled: P = 0.0014; S5P vs S5P + ANP32B: P = 0.0025; and S5P vs no peptide: P = 0.0002. Source data are provided as a Source data file.
