Infection Tunes the Dynamics of Adenoviral E1A Disordered Regions

Intrinsically Disordered Proteins and protein regions (IDPs) are abundant in many viral proteomes and play diverse roles in the viral infectious cycles. The adenovirus Early Protein 1A (E1A) is one such viral IDP. E1A acts as a molecular hub that regulates viral infection by mediating interactions between viral and multiple host proteins. Like other IDPs, E1A exists in a flexible ensemble of conformations. Despite a demonstrated link between ensemble structure and function in E1A, no real-time measurement of its ensemble has been performed. Here, we use live cell FRET microscopy to measure the local ensemble structure of E1A in human cells, both in healthy cells and in cells infected with adenovirus. We found specific disordered regions undergo significant changes to their ensemble in infected cells. Furthermore, infection also alters the propensity of these regions to partition between the cytoplasm and nucleus, a hallmark of E1A function during infection. Our results showcase that the structural ensembles of viral IDPs are responsive to infection, and suggest that these may play a role in regulating infection progression. SignificanceIntegral to many viral proteomes are intrinsically disordered proteins and protein regions (IDPs), which target and rewire cellular pathways to ensure infection progression. During this process, the physical and chemical composition of the cell changes dramatically: metabolism is rewired, viral proteins are produced en masse, and as a result, the chemical composition of the host proteome is significantly altered. IDPs are known to be structurally sensitive to even mild changes in their environment, and their structural changes can result in a change to function. Here, using live cell FRET microscopy, we show that the structure and spatial localization of an adenovirus IDP, E1A, is altered in cells infected by the virus. Beyond a possible functional role for structural sensitivity in viral IDP function, our findings suggest that host IDPs may also be structurally altered by infection, with downstream functional consequences.