Coffino, P. | Search bioRxiv

bioRxiv2025

Specific degrader for fusion oncokinase kills tumors and is augmented by bimodal degrader-siRNA

Oncogenic fusions of two native proteins are challenging to block without disturbing the parental proteins. A mRNA delivered peptide degrader, selectively eliminates the oncogenic fusions DNAJB1::PRKACA and ATP1B1::PRKACA in fibrolamellar carcinoma (FLC), cholangiocarcinoma and intraductal pancreatic neoplasm, without effect on native PRKACA. Specific degradation reflected structural properties of the fusion proteins. The degrader was lethal to FLC tumor cells in a preclinical model, with no effect on non-FLC cells. To enhance efficacy and speed, we modified the mRNA to simultaneously encode the degrader and an siRNA against the fusion transcript, reducing new protein synthesis which accelerated degradation of DNAJB1::PRKACA, offering a wide therapeutic index for mutation-driven disease.

cancer biology↗

bioRxiv2019

Allosteric coupling between alpha-rings of the 20S proteasome

The proteasomal machinery performs essential regulated protein degradation in eukaryotes. Classic proteasomes are symmetric, with a regulatory ATPase docked at each end of the cylindrical 20S. Asymmetric complexes are also present in cells, either with a single ATPase or with an ATPase and non-ATPase at two opposite ends. The mechanism that populates these different proteasomal complexes is unknown. Using archaea homologs, we constructed asymmetric forms of proteasomes. We demonstrate that the gate conformation of two opposite ends of 20S are coupled: binding one ATPase opens a gate locally, and also the remote opposite gate allosterically. Such allosteric coupling leads to cooperative binding of proteasomal ATPases to 20S, and promotes formation of proteasomes symmetrically configured with two identical ATPases. It may also promote formation of asymmetric complexes with an ATPase and a non-ATPase at opposite ends. We propose that in eukaryotes a similar mechanism regulates the composition of the proteasomal population.

biochemistry↗