Defender of cell death 1 (DAD1) was initially discovered in BHK21 cells as a negative regulator of programmed cell death, a process important for normal organism development and tissue homeostasis. DAD1 was later shown to be a subunit of the mammalian oligosaccharyltransferase complex and is required for its function and structural integrity. Mice lacking DAD1 express abnormal N-linked glycoproteins and undergo increased apoptotic-associated embryonic death. Furthermore, overexpression of DAD1 mRNA is seen in some human hepatocellular carcinomas, indicating it may also play a role in carcinogenesis. It should be noted that DAD1 is not related to the inhibitor of apoptosis proteins (IAP) family and does not contain any baculoviral IAP repeat (BIR) domains.
