Nucleolar beacon for monitoring nucleolar morphology and proteomics in living cells.

The nucleolus is essential for ribosome biogenesis and stress regulation. However, because of its dynamic nature, there is still a lack of methods to specifically visualize nucleolar localization in living cells and to study dynamic changes in protein interaction networks within the cell nucleolus. In this study, we identified and engineered a signal peptide sequence, termed nucleolar beacon, which exhibits robust nucleolar localization and universal applicability across various mammalian cell types. Using this sequence, we established nucleolar indicator cell lines and demonstrated their practicality in studying nucleolar functions in living cells. In addition, by combining the signal peptide with proximity labeling technology, we developed an effective approach for capturing the nucleolar proteome and successfully identified nucleolar-associated proteins. These techniques provide effective and versatile tools for investigating nucleolar functions in living cells and offer a potential strategy for drug delivery applications.