The effect of ubiquitin and ubiquitin-like modifier on DRiP Synthesis
PACH N. 1, BASLER M. 1,2
1 Universitšt Konstanz, Konstanz, Germany; 2 Biotechnology Institute Thurgau , Kreuzlingen, Switzerland
DRiPs are unfunctional proteins that are rapidly degraded during or after translation and were found to make an important source for MHC class I ligands. DRiPs are characterized to derive from a substantial subset of nascent gene products that degrade more rapidly than their corresponding native retiree pool. However, a specific DRiP was not described so far. In this study, we aimed to characterize and identify DRiPs derived from a viral protein. Using the nucleoprotein (NP) of the lymphocytic choriomeningitis virus (LCMV) which is conjugated N-terminally to ubiquitin, or the ubiquitin-like modifiers FAT10 or ISG15 the occurrence of DRiPs was studied. The formation and degradation of DRiPs was monitored by western blot with the help of a FLAG tag. Using this approach we identified several short lived DRiPs derived from LCMV-NP. Interestingly, this DRiPs could only be observed when the LCMV-NP was modified with ubiquitin or ubiquitin-like modifiers, but not in the wild type form. Using proteasome inhibitors, we could show that degradation of LCMV-NP derived DRiPs were proteasome dependent. Interestingly, the synthesis of DRiPs could be enhanced when cells were stressed with the help of FCS starvation. Furthermore, the NP-derived NP118-126 antigen presentation was studied in antigen presentation assays. Consistent to the observed DRiP formation described above, an enhanced NP118-126 presentation was observed when the LCMV-NP was modified with ubiquitin or ubiquitin-like modifiers, compared to the wild type form. Taken together, we visualize for the first time DRiPs derived from a viral protein. Our investigation of DRiPs in the MHC class I antigen presentation opens up new possibilities for the development of vaccination strategies.