Dissection of Poly(A)-binding protein (PABPC) cellular function using degron-mediated depletion with replacement

To enable structure–function analysis of PABPC in human cells, we developed a protein-replacement platform that couples rapid auxin-inducible degradation of endogenous PABPC1 and PABPC4 with doxycycline-controlled expression of engineered PABPC variants.

This approach enables acute removal of native PABPC and real-time assessment of how specific domains, paralogs, and sequence alterations support cellular fitness, shape transcriptome profiles, and regulate poly(A)-tail length. Using this system, we show that the RRM4 domain of PABPC1 is essential for growth, whereas post-translationally modified lysines within RRM4 are individually dispensable. Paralogs and variants with heterologous RRM4 domains vary in their ability to substitute for PABPC1, revealing functional divergence among PABPCs.