A Follistatin-Like Gene, mac25, as a Tumor Suppressor
mac25, a retinoic acid-inducible gene that is expressed at high levels in senescent epithelial cells (1), was initially cloned as a gene that is differentially expressed in meningioma (2). A murine homologue of mac25 (mmac25) was isolated from a lambda ZAP cDNA library constructed from the spleen of a p53-deficient mouse (3), as a clone with a growth-suppressing activity (4) against a p53-deficient osteosarcoma cell line (Saos 11). The cloned cDNA had 977 nucleotides and the product consisted of 238 amino acids. mmac25 exhibits 87.5% identity in terms of nucleotide sequence and 94.4% similarity in terms of amino acid sequence to human mac25 (4). Both mmac25 and mac25 have a signal sequence with unique leucine repeat at the amino terminus and one putative site of N-glycosylation (Fig. 31.1).
KeywordsCysteine Carboxyl Serine Resi Leucine
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