Scm Like With Four Mbt Domains Protein 1 (SFMBT1)

RU1 protein contains a nonapeptide at residues 34 to 42 that is recognized by specific CTLs when presented by HLA-B51-positive tumor cells containing a proteasome. However, the nonapeptide is not presented by Epstein-Barr virus-transformed B cells or by dendritic cells, both of which contain an immunoproteasome that is incapable of cleaving the antigenic peptide. Western blot analysis showed that the immunoproteasome, but not the proteasome, contains LMP2 (PSMB9) and LMP7 (PSMB8), possibly due to induction by gamma-interferon (IFNG). Further functional analysis showed that other, but not all, tumor antigens are less efficiently processed by IFNG-treated proteasomes. Peptides rather than full-length proteins requiring proteasome digestion may be more suitable as cancer vaccines.