5’Untranslated regions provide a versatile toolkit for tunable exogenous protein expression

Protein overexpression remains a pervasive limitation in transient transfection experiments, as commonly used strategies provide coarse, labor-intensive, and often unpredictable control over protein abundance, frequently leading to artifacts or loss of physiological relevance.A compact, modular 5'UTR toolkit enables fine-grained and scalable control of protein abundance in transient transfection, providing a reproducible dynamic range across soluble and membrane proteins outperforming promoter swapping for continuous tuning of expression levels.Tunable expression improves experimental fidelity across diverse applications, allowing investigators to match protein abundance to specific assay needs, reducing overexpression artifacts, preserving physiological readouts, and enhancing yield when high expression is required.