FIG. 1.
State-of-the-art models of IE1 presentation and evasion. (Left) IE1 presentation model, based on references 8, 10, 49, and 53. In the IE phase, and in particular under IE conditions enforced by the metabolic inhibitors cycloheximide and actinomycin D, the IE1 protein pp89 encoded by gene ie1 is expressed and processed, and the nonapeptide YPHFMPTNL is presented in the haplotype H-2d by the MHC-I molecule Ld. (Right) IE1 immune evasion model, based on references 6, 7, 47, 63, and 67. In the E phase of viral gene expression, gp37/40 encoded by gene m152 causes the retention of peptide-loaded MHC-I molecules in the ER-Golgi intermediate compartment (ERGIC) and cis-Golgi, thereby preventing the presentation of the IE1 peptide. It is proposed that lack of MHC-I surface expression renders the E-phase cells susceptible to recognition by NK cells.