Diversity Supplement Project Summary The ability of cancer cells to adapt to a wide variety of stress conditions plays a critical role in various physiological facets of tumorigenesis. We recently reported the discovery of stress-induced noncoding RNA derived from stimuli-specific loci of the ribosomal intergenic spacer (rIGSRNA); an enigmatic region of the human genome historically dismissed as “junk” DNA. We showed that rIGSRNA activate a physiological amyloidogenic program that converts nucleoli into Amyloid-bodies: reversible nuclear membrane-less compartments composed of immobilized proteins in an amyloid-like state. While many cellular bodies have been described as liquid-like (e.g., stress granules, P-bodies, germ cell granules), the discovery of Amyloid-bodies provided evidence of an amyloidogenic program that can physiologically transition biological matter to a solid state. Amyloid-bodies are found in sub-populations of cells in normal tissues, the core of low-grade human tumors and cells responding to various stimuli highlighting their ubiquitous nature. Proteomic analysis revealed that Amyloid-bodies immobilize participants of the DNA synthesis machinery and cell cycle control, amongst many other metabolic regulators. Intriguingly, Amyloid-bodies share many biophysical properties with the amyloidogenic, solid-like Balbiani-bodies involved in metabolic suppression in Xenopus. Likewise, yeast solidify elements of their proteome to sporulate and arrest growth in non-permissive conditions. This raises the fascinating possibility that stressed cancer cells assemble Amyloid-bodies to enter a spore-like state of extreme metabolic depression. We recently showed that rIGSRNA coordinate a RNA tailing program mediated by their interactions to Terminal NucleotidylTransferases 4b (TENT4b) to drive Amyloid-bodies biogenesis. This post-translational pathway enables cancer cells to immobilize elements of the DNA synthesis machinery and halt oncogenic signaling in an adaptive response to severe environmental insults In this Diversity Supplement Proposal, Ms. Rios will focus her efforts on three goals that a included in Specific Aim #2 and #3 of the Parental NCI R01. Based on these preliminary and published results, we hypothesize that “RNA tailing program drives amyloidogenic phase transition to induce metabolic suppression of cancer cells”. We plan to test this hypothesis by: 1- Test the role of rIGSRNA/TENT4b interactions in phase transition and 2- Examine the role of phase transition in clinical samples and orthotopic tumor models. The discovery of dedicated enzymatic programs that drive physiological amyloidogenesis provides a unique opportunity to study the role of liquid-to-solid phase transition in human clinical samples and in vivo tumor assays. By studying clinical samples, in culture and orthotopic animal models, we will test if phase transition induces a unique and yet uncharacterized cancer cell state of extreme metabolic depression, while...