PSME1 Human

Proteasome Activator Subunit 1 (PA28α), also known as PSME1, is a protein encoded by the PSME1 gene in humans. This protein plays a crucial role in the regulation of the proteasome, a complex responsible for degrading unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds.

The proteasome is a multicatalytic proteinase complex with a highly ordered structure composed of two complexes: a 20S core and a 19S regulator. The 20S core is made up of four rings of 28 non-identical subunits, while the 19S regulator consists of a base with six ATPase subunits and two non-ATPase subunits, and a lid with up to ten non-ATPase subunits .

PA28α is a subunit of the 11S regulator, also known as the PA28 activator complex. This complex enhances the generation of class I binding peptides by altering the cleavage pattern of the proteasome, which is essential for efficient antigen processing . The 11S regulator replaces the 19S regulator in the immunoproteasome, a modified proteasome involved in the processing of class I MHC peptides .

PA28α is induced by gamma-interferon and is involved in the assembly of the immunoproteasome, which is crucial for generating tumor antigens presented by MHC class I molecules . This process is vital for the immune system’s ability to recognize and eliminate cancerous cells.

High expression of PA28α has been associated with poor survival in patients with soft tissue leiomyosarcomas, a type of cancer. Studies have shown that high nuclear expression of PA28α predicts poor survival and decreased metastasis-free survival in these patients . This makes PA28α a potential prognostic biomarker for certain types of cancer.