The 26S proteasome is a multicatalytic proteinase complex with a highly ordered structure composed of 2 complexes a 20S core and a 19S regulator The 20S core is composed of 4 rings of 28 non-identical subunits 2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits Proteasomes are distributed throughout eukaryotic cells at a high concentration and cleave peptides in an ATP ubiquitin-dependent process in a non-lysosomal pathway This gene encodes a member of the peptidase T1A family that functions as a 20S core alpha subunit The encoded protein interacts with the hepatitis B virus X protein and plays a role in regulating hepatitis C virus internal ribosome entry site (IRES) activity an activity essential for viral replication The encoded protein also plays a role in the cellular stress response by regulating hypoxia-inducible factor-1alpha A pseudogene of this gene is located on the long arm of chromosome 9