The role of the proteasome activator PA28 in MHC class I antigen processing.

The proteasome system is the major source for the generation of viral antigens and tumor antigens presented by major histocompatibility complex class I (MHC class I) molecules. A specific feature of the proteasomal antigen processing machinery is that five of its components are inducible by IFN-gamma. Two of these are the alpha and beta subunits of the proteasome activator PA28.