Protein splicing for immunity

Eukaryotic cells can make several protein variants from one gene via RNA splicing. Now, a chance encounter with an antigen suggests to Ken-ichi Hanada, Jonathan Yewdell, and James Yang (National Institutes of Health, Bethesda, MD) that vertebrate cells might get even more mileage from the genome through protein splicing.

Yang's group shows that protein splicing produces a fragment of the FGF-5 protein that is recognized as antigenic by human T cells. T cell recognition was stimulated by a peptide as short as nine residues, as long as it contained two short sequences normally separated within full-length FGF-5 by 40 amino acids. Production of the fusion is posttranslational, as untreated cells could process longer synthetic peptides into active antigens, but lightly fixed cells (which are unable to do their own proteolytic processing) could present...