RNA is an attractive biomolecule for biosensing and engineering applications due to its information storage capacity and ability to drive gene expression or knockdown. However, methods to link chemical signals to the production of specific RNAs are lacking. Here, we develop protease-responsive RNA polymerases (PRs) as a strategy to encode multiple specific proteolytic events in defined sequences of RNA in live mammalian cells. This work demonstrates that RNAP-based molecular recording devices can be deployed for multimodal analyses of biochemical activities or to trigger gene circuits using measured signaling events.