Image: Recent research from the Garfinkel Lab uncovers new functions for a region in the retrovirus-like retrotransposon Ty1 was recently published in Proceedings of the National Academy of Sciences (https://www.pnas.org/doi/10.1073/pnas.2303358120). They describe a novel prion-like domain (PrLD) in the Ty1 Gag protein in yeast. Gag, also found in retroviruses like HIV, is the structural protein that assembles virus-like particles (VLPs). Retrotransposons replicate within VLPs; however, how their building blocks associate and assemble within the cell is poorly understood. The PrLD has similar sequence properties to prions and disordered protein domains that can drive the formation of assemblies that range from liquid to solid. The Ty1 PrLD is essential for transposition, but they were able to restore transposition by replacing the Ty1 PrLD with similar disordered sequences from yeast and mouse prions. These findings uncover a critical function for often overlooked disordered sequences, demonstrate greater flexibility in VLP assembly than previously appreciated, and establish an interchangeable "plug-and-play" platform to study disordered sequences in living cells using the power of yeast genetics. Congratulations to Dr. Sean Beckwith, Emily Nomberg, Abigail Newman, and Dr. David Garfinkel!