A HaloTag-Based Reporter System Enabling Two-Color Timestamped Gene Expression Monitoring.

Precise gene expression regulation is essential for cellular homeostasis, particularly in stress response pathways. In the endoplasmic reticulum, the unfolded protein response (UPRER) plays an important role in maintaining the protein folding capacity. We developed a chemigenetic gene expression reporter system for BiP/GRP78, a key regulator of the UPRER, based on co-expression of the self-labeling HaloTag protein. We designed a two-color sequential labelling strategy for improved readout sensitivity and applied our system in a high-content screening, identifying a promising novel activator of BiP/GRP78 expression.