The function of HYOU1 (hypoxia up-regulated 1, ENSG00000149428) is as follows. Has a pivotal role in cytoprotective cellular mechanisms triggered by oxygen deprivation. Promotes HSPA5/BiP-mediated ATP nucleotide exchange and thereby activates the unfolded protein response (UPR) pathway in the presence of endoplasmic reticulum stress (By similarity). May play a role as a molecular chaperone and participate in protein folding. {ECO:0000250|UniProtKB:Q9JKR6, ECO:0000269|PubMed:10037731}.