NACA1, NACA2 and NACAP1 are members of the nascent polypeptide-associated complex (NAC) α subunit family that participate in preventing inappropriate targeting of non-secretory polypeptides to the endoplasmic reticulum (ER). As nascent polypeptide chains emerge from the ribosome, NACA proteins bind to these chains and block their interaction with the signal recognition particle (SRP), which normally targets nascent secretory peptides to the ER. Members of the α-NAC subunit family have sequence similarities with transcription-regulating proteins and are suggested to function as transcriptional coactivators potentiating c-Jun-mediated transcription. Most NACA proteins localize to both nucleus as well as cytoplasm, and contain NAC-A/B (NAC-α/β) and UBA (ubiquitin-associated) domains. The UBA domain is associated with proteins involved in the ubiquitin-proteasome pathway for protein degradation.