Molecular cloning of a novel RING finger-B box-coiled coil (RBCC) protein, terf, expressed in the testis

RING finger is a variant zinc finger motif present in a new family of proteins including transcription regulators. Here, utilizing the polymerase chain reaction with degenerate primers, we isolated a genomic DNA fragment containing the RING finger motif. Using this fragment as a probe, we have identified a novel cDNA from rat testis library. Then, the human homologue of the terf cDNA was also isolated from a testis library. This gene was designated testis RING finger protein (terf) because the corresponding transcripts were detected almost exclusively in the testis by Northern blot analysis. Both cDNAs encode an open reading frame of 477 amino acids sharing high homology (74% identity at the protein level) between two species. The terf contains an N-terminal RING finger domain, one B-box domain, middle coiled-coil domain, and a C-terminal domain, belonging to the RING finger-B box-coiled coil (RBCC) family. Several RBCC proteins, such as PML, TIF1alpha and RFP, have transformation capabilities when found in chromosomal translocations. Among the members of the RBCC family, the terf shares highest homology (40% identity at the protein level) with RFP that is expressed only in the testis in normal tissues. Structural similarity raises the possibilities that the terf gene might be also involved in carcinogenesis or cell transformation.