MOLECULAR-CLONING OF A CDNA WITH A NOVEL DOMAIN PRESENT IN THE TRE-2 ONCOGENE AND THE YEAST-CELL CYCLE REGULATORS BUB2 AND CDC16

Tn an effort to identify genes that are differentially regulated durin g mast cell development, subtracted cDNA prepared from wild-type murin e P815 mastocytoma cells and a P815 subline that exhibits properties o f mast cell differentiation was used to screen mast cell cDNA librarie s. Several known mast cell-specific cDNAs were isolated including mast cell carboxypeptidase A (MC-CPA), murine mast cell protease-5 (MMCP-5 ), and gp49. A novel cDNA, designated Tbc1, was identified that showed differential expression in the two mast cell lines. The amino acid se quence predicted from the cDNA contains a 200 amino acid domain that i s homologous to regions in the tre-2 oncogene and the yeast regulators of mitosis, BUB2 and cdc16. The N-terminal region contains a number o f cysteine and histidine residues, potentially encoding a zinc finger domain. Tbc1 is a nuclear protein and is expressed in highest levels i n hematopoietic cells, testis and kidney. Within these tissues, expres sion of Tbc1 is cell- and stage-specific. Based on sequence similarity , pattern of expression and subcellular localization, Tbc1 may play a role in the cell cycle and differentiation of various tissues.