The Bop gene adjacent to the mouse CD8b gene encodes distinct zinc-finger proteins expressed in CTLs and in muscle.

The Bop gene (for CD8b opposite) is located immediately upstream of the mouse CD8b gene. Expression of Bop gene transcripts was previously observed in several long term CTL lines and in thymus. The present studies demonstrate that expression of the Bop gene in lymphocytes appears to be confined to CD8-positive cells, and that Bop gene expression is inducible by Con A. They further show that a single Bop gene encodes protein products with distinct amino-terminal sequences that are expressed in CTLs (t-BOP) and in cardiac and skeletal muscle (skm-BOP), as well as what appears to be a noncoding cDNA (t-ncb) expressed only in CTLs. The t-BOP and t-ncb cDNAs in CTLs result from alternative splicing of a single primary transcript, whereas the Bop transcripts expressed in CTLs and in muscle appear to be transcribed from different promoters. The BOP proteins expressed in CTLs and muscle contain zinc finger-like motifs with homology to those of the ETO/MTG8 proto-oncogene and several other proteins of interest. Western blot analysis with a hamster anti-BOP mAb have detected the BOP protein in muscle cells and in COS 7 cells transfected with Bop cDNA constructs.