Antibodies to OGFr-ARF detect two proteins in the melanoma cell line K008. Nuclear and cytoplasmic (S100) extracts were size fractionated on an 8% acrylamide gel and probed with antibodies to OGFr-ARF. Two proteins were detected, a nuclear protein (p174) and a protein detected in both the nuclear and cytoplasmic fractions (p54). Antibody specificity was demonstrated by the ability of OGFr-ARF peptide, but not of a MUC1 peptide, to block detection.