Activation of mast cells results in the generation and release of bioactive mediators which in turn initiate allergic inflammation. Mast cell function is enhanced following stimulation in part because of the induction of specific genes and their products. To identify additional genes induced in mast cells that support this process, we thus constructed an activation-specific mast cell subtraction library. To date, we have isolated 26 novel inducible murine mast cell (imc) cDNA clones. Among them, a full-coding region of the murine geneimc-415 was found to have a greater than 90% nucleotide sequence homology and a 97.5% amino acid sequence homology to both a human β4integrin-binding protein (p27BBP) and a human translation initiation factor 6 (eIF6), which in turn are identical.In vitrotranslation of theimc-415 gene yielded a band of an approximately 26 kDa. This is the same as the calculated molecular weight of murine IMC-415 protein based on the predicted amino acid sequence and is the molecular weight of p27BBP/eIF6. Murineimc-415 message was also induced in inflamed lung tissues in a mouse model of asthma. These results suggest a role for murineimc-415 in allergic inflammation where it may enhance protein synthesis. Human eIF6/p27BBPmay also play a role in allergic diseases based on the similarities in sequence and in gene expression patterns.