Immunogen sequence: LTRGAKEEHG GLIRSPRHEK KKKVRKYWDV PPPGFEHITP MQYKAMQAAG QIPATALLPT MTPDGLAVTP TPVPVVGSQM TRQARRLYVG NIPFGITEEA. U2 auxiliary factor (U2AF), comprised of a large and a small subunit, is a non-snRNP protein required for the binding of U2