In vivo pulse-chase in Caenorhabditis elegans reveals intestinal histone turnover changes upon starvation.

The ability to study protein dynamics and function in the authentic context of a multicellular organism is paramount to better understand biological phenomena in animal health and disease. Pulse-chase of self-labeling fusion protein tags provides the opportunity to label proteins of interest and track those proteins over time. There are currently several challenges associated with performing in vivo protein pulse-chase in animals, such as cost, reproducibility, and accurate detection methods. The Caenorhabditis elegans model organism has attributes that alleviate many of these challenges. This work tests the feasibility of applying the Halo modified enzyme (HaloTag) for in vivo protein pulse-chase in C. elegans. HaloTag intestinal histone reporters were created in the worm and used to demonstrate that reporter protein could be efficiently pulse-labeled by soaking animals in ligand. Labeled protein stability could be monitored over time by fluorescent confocal microscopy. Further investigation revealed reporter protein stability was dependent on the animal's nutritional state. Chromatin immunoprecipitation and sequencing of the reporters showed incorporation in chromatin with little change hours into starvation, implying a lack of chromatin regulation at the time point tested. Collectively, this work presents a straightforward method to label and track proteins of interest in C. elegans that can address a multitude of biological questions surrounding protein stability and dynamics in this animal model.