Cytosolic proteins are targeted to degradation by the proteasome in a selective process that is mediated by the ubiquitin-tagging machinery. MHC class I molecules bind the short peptides, generated by proteasomal degradation, and present them on the cell surface to cytotoxic T cells. We have demonstrate that changing the direction of substrate translocation into the proteasome affects presentation level of specific epitopes on MHC class I molecules. We also showed that the maturation phase of the protein sent to proteasomal breakdown influences MHC class I epitope presentation level as well. Currently, we continue to study the correlation between the mode of substrate degradation and antigen presentation both in vitro and in vivo.
