The N-terminal Flanking Region of the TRP2 sub(360-368) Melanoma Antigen Determines Proteasome Activator PA28 Requirement for Epitope Liberation

• Published in: The Journal of biological chemistry 2007-04, Vol.282 (17), p.12749-12754
• Main Authors: Textoris-Taube, Kathrin, Henklein, Peter, Pollmann, Sylvie, Bergann, Theresa, Weisshoff, Hardy, Seifert, Ulrike, Drung, Ilse, Muegge, Clemens, Sijts, Alice, Kloetzel, Peter-Michael, Kuckelkorn, Ulrike
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X

Proteasomes are known to produce major histocompatibility complex (MHC) class I ligands from endogenous antigens. The interferon- gamma -inducible proteasome activator PA28 plays an important role in the generation of MHC ligands by proteasomes. Generation of the HLA-A super(*)0201 restricted melanoma antigen TRP2 sub(360-368) by the proteasome has been shown to be dependent on the function of PA28 in vitro and in vivo (Sun, Y., Sijts, A. J., Song, M., Janek, K., Nussbaum, A. K., Kral, S., Schirle, M., Stevanovic, S., Paschen, A., Schild, H., Kloetzel, P. M., and Schadendorf, D. (2002) Cancer Res. 62, 2875-2882). Here we analyzed the role of the epitope sequence environment in determining this PA28 dependence. Experiments using the melanoma TRP2 sub(288-296) epitope and the murine cytomegalovirus-derived pp89 epitope precursor peptide for epitope replacement revealed that the TRP2 sub(360-368) flanking sequences can transfer PA28 dependence onto otherwise PA28 independent epitopes. Moreover, the N-terminal flanking sequence is sufficient to establish PA28 dependence of an epitope by allowing PA28-induced coordinated dual cleavages. These results show that N-terminal flanking sequences strongly influence epitope generation efficiency and that PA28 function is particularly relevant for the generation of normally poorly excised peptide products.