The Ebolavirus Transcription Regulatory Signal Equilibrates Between Two Structural Conformations to Affect VP30 Binding.

The transcription of ebolavirus (EBOV) genomes is a major checkpoint in the viral life cycle. Altering the transcription regulatory signal (TRS), an RNA hairpin that forms in the 3' leader sequence of EBOV, affects transcription in a VP30-dependent manner. How this mechanistically occurs is currently unknown. Here, we find that the TRS primarily equilibrates between two structures that differ in their loops. Mutational studies demonstrate that the entire hairpin structure is important in directing both VP30 binding and regulating EBOV transcriptional activity, with the loop being the principal structural element. In doing so, we highlight that the TRS structure is a critical determinant of EBOV transcription.