In vivo pulse-chase in C. 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 tag fusion proteins provide 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 C. 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. ChIP-seq 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. Overall design: ChIP-seq on intestine-specific his-58/H2B and his-9/H3.1 reporter protein from his-58/H2B or his-9/H3.1 C. elegans reporter strains. N2 (WT) was included as an ChIP negative control.  his-58/H2B and his-9/H3.1 reporter strains were either fed or starved prior to ChIP-seq processing.