An ER stress-responsive RNA rheostat for programmable gene and mRNA therapies.

Therapeutic protein overexpression can overwhelm endoplasmic reticulum (ER) folding capacity, trigger unfolded protein response (UPR) signaling, and compromise the safety of gene and mRNA therapies. Here, we engineer stress-responsive RNA rheostats that couple transgene expression to endogenous ER stress sensing. Short RNA elements derived from X-box-binding protein 1 (XBP1) mRNA undergo inositol-requiring enzyme 1α (IRE1α)-dependent splicing under ER stress, inducing a frameshift that attenuates downstream protein expression. XBP1 switches function across DNA and mRNA delivery platforms and regulate the expression of fluorescent reporters, coagulation factor VIII, and Leronlimab, a therapeutic anti-CCR5 monoclonal antibody. Switch activation reduces ER stress markers while preserving expression under homeostatic conditions. We further demonstrate the regulation of Leronlimab expression in vivo using recombinant adeno-associated virus vectors. Together, these findings establish programmable RNA feedback control as a strategy for linking cellular proteostasis to therapeutic protein expression and improving the safety of gene and mRNA therapies.