API5 Full-Length MS Protein Standard (NP_001136403), Labeled with [U- 13C6, 15N4]-L-Arginine and [U- 13C6, 15N2]-L-Lysine, was produced in human 293 cells (HEK293) with fully chemically defined cell culture medium to obtain incorporation efficiency at Creative-Proteomics. This gene encodes an apoptosis inhibitory protein whose expression prevents apoptosis after growth factor deprivation. This protein suppresses the transcription factor E2F1-induced apoptosis and also interacts with, and negatively regulates Acinus, a nuclear factor involved in apoptotic DNA fragmentation. Its depletion enhances the cytotoxic action of the chemotherapeutic drugs. Multiple alternatively spliced transcript variants encoding different isoforms have been identified.