Identification of L-FILIP as MKRN1-induced ubiquitinated proteins. Ubiquitinated proteins of 80 and 82 kDa in Fmkrn-24 cells were immunoprecipitated with anti-ubiquitin antibody followed by SDS-polyacrylamide gel electrophoresis. The gel pieces containing the 80- and 82-kDa proteins were excised, and the tryptic peptides were analyzed by mass spectrometry. Amino acid sequences of L-FILIP are shown. The identical amino acids sequences between the analyzed peptides and L-FILIP are shown by underlines.