This method proves effective in bacteria, human cells, and live tumor models, enabling a more ethical examination of intricate diseases such as cancer.
This significant advancement tackles a persistent issue in biology: monitoring subtle alterations in proteins, referred to as post-translational modifications, within living organisms. These modifications function as on/off switches for numerous processes, such as growth, aging, and disease.
Instead of disrupting cells or employing invasive methods, the research team designed cells to generate a luminescent lysine variant. When these switches are activated, the luminescence offers immediate visibility, granting scientists a fresh insight into the fundamental mechanisms of life.
This system lets us see the invisible choreography of proteins inside living cells. By equipping cells with the tools to produce and sense a new amino acid, we unlock a direct window into how PTMs drive biological processes in living animals.
Han Xiao, Study Corresponding Author and Professor, Chemistry, Bioengineering and Biosciences, Rice University
Han Xiao is also a Cancer Prevention and Research Institute of Texas Scholar.
Chromophoric Proof of Concept
The initiative commenced with the premise that enabling cells to autonomously generate and utilize a 21st amino acid would surpass conventional techniques that rely on supplying cells with substantial amounts of synthetic labels.
The research team discovered and utilized enzymes to synthesize acetyllysine within the cells. Subsequently, the team genetically modified bacteria and human cells to integrate it into proteins at designated locations.
Reporter proteins, including a fluorescent protein or an enzyme, emit light when post-translational modifications (PTMs) are introduced or eliminated, thereby confirming the system’s efficacy for real-time monitoring.
“This innovative method goes beyond previous approaches by eliminating the need for external chemicals and allowing us to watch protein changes happen naturally inside living cells,” said Xiao.
PTMs and Cancer Research
The researchers employed the sensors to investigate the deacetylase SIRT1 and illustrate its functionality. SIRT1 is a posttranslational regulator involved in modulating inflammation, which has been a topic of extensive discussion in cancer biology.
The inhibition of SIRT1 blocked its enzymatic activity; however, contrary to some anticipations, it did not hinder tumor growth in specific cell lines.
Seeing a glow in response to acetylation events inside living tissue was thrilling. It makes the invisible world of protein regulation vividly observable and opens new possibilities for studying disease mechanisms and drug actions.
Han Xiao, Study Corresponding Author and Professor, Chemistry, Bioengineering and Biosciences, Rice University
Broader Applications and Future Outlook
The engineered cells can potentially transform how scientists investigate PTMs in fields such as aging and neurological disorders. Their functionality within living organisms allows for real-time monitoring of diseases or treatments, and their light-based signals are particularly advantageous for extensive drug screening aimed at PTM-regulating enzymes.
Future advancements may broaden this methodology to encompass additional forms of PTMs or organoid systems derived from humans, thereby enhancing the platform's significance for personalized medicine and offering a more profound understanding of cellular regulation.
“With this living sensor technology, our research offers an innovative tool that illuminates the dynamic world of PTMs, promising to reshape our understanding and treatment of diseases rooted in protein regulation by transforming invisible molecular signals into visible biological narratives,” said Yu Hu, Study First Author and Postdoctoral Researcher at Rice University.
The authors collaborating on this study comprise Yixian Wang, Linqi Cheng, Chenhang Wang, Yijie Liu, Yufei Wang, Yuda Chen, Shudan Yang, Yiming Guo, Shiyu Jiang, and Kaiqiang Yang from Rice University.
The study was funded by the SynthX Seed Award, the National Institutes of Health, the Robert A. Welch Foundation, the U.S. Department of Defense, and the Robert J. Kleberg Jr. and Helen C. Kleberg Foundation.
Journal Reference:
Hu, Y., et al. (2025) Engineering unnatural cells with a 21st amino acid as a living epigenetic sensor. Nature Communications. doi.org/10.1038/s41467-025-64448-1