RING finger is a variant zinc finger motif present in a new family of proteins including transcription regulators. A genomic DNA fragment containing RING finger motifs was identified by the polymerase chain reaction using degenerate primers. Using this fragment as a probe, we have isolated a novel cDNA from rat brain library. The predicted open reading frame contains a RING finger domain at its N-terminal portion. The corresponding transcript was detected predominantly in the brain and therefore was designated brain finger protein (bfp). An antibody raised against a recombinant bfp reveals the presence of the bfp in the brain. Interestingly, the bfp is induced during retinoic acid-mediated differentiation of P19 embryonal carcinoma cells into neural cells. These findings suggest the possible involvement of bfp in some aspects of neural cell regulation.