Quantitative photoconversion analysis of internal molecular dynamics in stress granules and other membraneless organelles in live cells.

Photoconversion enables real-time labeling of protein sub-populations inside living cells, which can then be tracked with submicrometer resolution. Here, we detail the protocol of comparing protein dynamics inside membraneless organelles in live HEK293T cells using a CRISPR-Cas9 PABPC1-Dendra2 marker of stress granules. Measuring internal dynamics of membraneless organelles provides insight into their functional state, physical properties, and composition. Photoconversion has the advantage over other imaging techniques in that it is less phototoxic and allows for dual color tracking of proteins. For complete details on the use and execution of this protocol, please refer to Amen and Kaganovich (2020).