Corbat, A. | Search bioRxiv

bioRxiv2026

Oncomimetic β-catenin activity onset, duration and region defines aberrant intestinal development

In early intestinal carcinogenesis, adenoma formation is commonly initiated by loss-of-function mutations in a tumor suppressor that lead to oncoprotein gain-of-function, like in the tumor suppressor-oncoprotein pair APC-{beta}-catenin. Small intestinal organoids provide an in vitro system to study consequences of such mutations on tissue organization. However, conventional genetic manipulations do not allow precise control over the onset and duration of oncoprotein activity to study their influence on tissue transformation. Furthermore, homogenous tissues of clonal genetic models do not readily capture cellular interaction among mutated and neighboring wildtype tissue during early transformation. To mimic oncogenic activation of {beta}-catenin, we established a chemical-(opto)genetic approach to gain bio-orthogonal acute, spatial and temporal control over {beta}-catenin oncoprotein stability and relate oncoprotein levels to morphological development of mouse small intestinal organoids. We identified aberrant phenotypes that result from bio-orthogonally induced oncoprotein activity but persist even after oncoprotein depletion. Furthermore, local activation of oncomimetic {beta}-catenin activity within the stem cell niche leads to aberrant differentiation during homeorhesis and homeostasis, recapitulating early events of tissue transformation.

cancer biology↗

bioRxiv2023

Molten globule driven and self-downmodulated phase separation of a viral factory scaffold

Viral factories of liquid-like nature host transcription and replication in most viruses. The syncytial respiratory virus factories include gene function proteins, brought together by the phosphoprotein (P) RNA polymerase cofactor, present across non-segmented negative stranded RNA viruses. Homotypic liquid-liquid phase separation of RSV-P is governed by an -helical molten globule domain, and strongly self-downmodulated by adjacent sequences. Condensation of P with the nucleoprotein N is stoichiometrically tuned, defining aggregate-droplet and droplet-dissolution boundaries. Time course analysis show small N-P nuclei gradually coalescing into large granules in transfected cells. This behavior is recapitulated in infection, with small puncta evolving to large viral factories, strongly suggesting that P-N nucleation-condensation sequentially drives viral factories. Thus, the tendency of P to undergo phase separation is moderate and latent in the full-length protein but unleashed in the presence of N or when neighboring disordered sequences are deleted. This, together with its capacity to rescue nucleoprotein-RNA aggregates suggests a role as a "solvent-protein" and possible fluidity tuner of viral factories.

biophysics↗