| We mapped a major autoimmune epitope in XRCC 4 and found that it encompassed a DNA dependent protein kinase phosphorylation site , which is located at serine 260 ; that it was adjacent to a site for caspase 3 , which cleaves after residue 265 ; and that it also spanned a site for the inflammatory protease , granzyme B , which cleaves after residue 254 . ^^^ |