Using a thymocyte cell line model, the study demonstrated that hEndoU exhibits robust calcium-dependent ribonuclease activity, confirmed through knockout and rescue experiments.

Recent research highlights the crucial role of calcium ions in activating human EndoU (hEndoU), a key enzyme involved in various cellular processes.

The study reveals that calcium not only activates hEndoU but also enhances its interaction with RNA, enabling specific cleavage at uridylate sites, which is vital for its biological functions.

Employing advanced techniques such as NMR spectroscopy and cryo-electron microscopy, researchers elucidated the structural changes in hEndoU that occur upon calcium binding.

This activation mechanism is particularly significant as it contrasts with some bacterial and viral EndoUs, which do not require cofactors for activation.

EndoU is essential in various cellular processes, including RNA maturation, viral defense, and immune responses, and has also been identified as a biomarker in several cancers.

Structural analysis further reveals a calcium-stabilized interaction network that involves residues from both the eukaryote-specific N-terminal extension and the catalytic core of EndoU, activating its catalytic triad.