Proximity labelling and evolutionary evidence reveal insights into IL-1α nuclear networks and function

Interleukin (IL)-1 is a suggested dual-function cytokine that diverged from IL-1{beta} in mammals potentially by acquiring additional biological roles that relate to highly conserved regions in the pro-domain of IL-1, including a nuclear localisation sequence (NLS) and histone acetyl transferase (HAT)-binding domains. Why evolution modified pro-IL-1s subcellular location and protein interactome, and how this shaped IL-1s intracellular role, is unknown. TurboID proximity labelling with pro-IL-1 suggested a nuclear role for pro-IL-1 that involved interaction with HATs, including EP300. We also identified and validated inactivating mutations in the pro-IL-1 NLS of multiple mammalian species. However, HAT-binding domains were also conserved in species that had lost pro-IL-1 nuclear localisation. Together, these data suggest that HAT binding and nuclear localisation occurred together, and that while some species lost the NLS in their pro-IL-1, HAT binding was maintained. The NLS was lost from several distinct species at different evolutionary times, suggesting convergent evolution, and that the loss of the NLS confers some important biological outcome.