Leucine-tRNA Initiates at CUG Start Codons for Protein Synthesis and Presentation by MHC Class I

作者：Starck Shelley R; Jiang Vivian; Pavon Eternod Mariana; Prasad Sharanya; McCarthy Brian; Pan Tao; Shastri Nilabh^*

来源：Science, 2012, 336(6089): 1719-1723.

DOI：10.1126/science.1220270

Effective immune surveillance by cytotoxic T cells requires newly synthesized polypeptides for presentation by major histocompatibility complex (MHC) class I molecules. These polypeptides are produced not only from conventional AUG-initiated, but also from cryptic non-AUG-initiated, reading frames by distinct translational mechanisms. Biochemical analysis of ribosomal initiation complexes at CUG versus AUG initiation codons revealed that cells use an elongator leucine-bound transfer RNA (Leu-tRNA) to initiate translation at cryptic CUG start codons. CUG/Leu-tRNA initiation was independent of the canonical initiator tRNA (AUG/Met-tRNA(i)(Met)) pathway but required expression of eukaryotic initiation factor 2A. Thus, a tRNA-based translation initiation mechanism allows non-AUG-initiated protein synthesis and supplies peptides for presentation by MHC class I molecules.

• 出版日期2012-6-29