HYOU1 also known as OPR150 belongs to the heat shock protein 70 family. HYOU1′s localization within the ER is crucial, as HYOU1 plays a significant role in the proper folding and secretion of proteins, particularly in tissues with high secretory demands, such as the liver and pancreas. HYOU1′s ability to assist in protein maturation is vital for maintaining cellular homeostasis, especially under conditions of stress like hypoxia, where HYOU1 helps protect cells from apoptosis. Notably, HYOU1 expression is often upregulated in various tumors, including breast cancer, indicating HYOU1′s potential involvement in tumorigenesis and suggesting HYOU1 may serve as a biomarker for cancer progression. The gene encoding HYOU1 features two translation initiation sites, leading to a truncated form that lacks an ER signal peptide but functions as a housekeeping protein in the cytoplasm.