Bcl-2-associated athanogene 1 (BAG-1) was first identified as an anti-apoptotic bcl-2-binding protein. Later it was found to bind the molecular chaperones Hsp70 and Hsc70 through its carboxy-terminal sequence (termed the Bag domain), resulting in the inhibition of the refolding activity of these chaperones. It is thought that by binding and inhibiting these molecular chaperones, BAG-1is able to modulate the expression level of proteins requiring chaperones to fold correctly. One such group of proteins that are affected is glucocorticoid receptors. Other reports have suggested that the level of BAG-1 expression correlates with the aggressiveness of various cancers. Multiple isoforms of BAG-1 are known to exist.