MYL6B is a regulatory myosin light chain that functions beyond traditional muscle contraction to regulate critical cellular pathways. In its canonical role, MYL6B serves as a regulatory light chain component of myosin II complexes, participating in cytoskeletal organization and muscle contraction 1. However, recent evidence reveals non-canonical functions: MYL6B binds to MDM2 and p53, facilitating MDM2-mediated p53 ubiquitination and degradation as part of non-muscle myosin II holoenzymes 1. This oncogenic function is particularly significant in hepatocellular carcinoma (HCC), where MYL6B is overexpressed and associated with poor prognosis; MYL6B knockout suppresses HCC cell clonogenicity and increases apoptosis 1. Beyond cancer, MYL6B serves as a gravity-responsive protein in skeletal muscle, with altered expression indicating shifts toward slow-twitch fiber types during gravitational loading changes 2. MYL6B expression is also upregulated in response to anti-cachectic factors like neuregulin-1β in heart failure-associated muscle wasting 3, and it emerges as a potential blood-based biomarker in breast cancer, particularly in luminal-A subtypes 4. Additionally, MYL6B is highly expressed in hematopoietic stem and progenitor cells with enhanced stemness capacity 5. These findings establish MYL6B as a multifunctional protein linking cytoskeletal organization, p53 regulation, and stem cell biology.