REPETIN (RPTN), A NEW MEMBER OF THE FUSED GENE SUBGROUP WITHIN THE S100 GENE FAMILY ENCODING A MURINE EPIDERMAL DIFFERENTIATION PROTEIN

We report the cloning and characterization of a murine epidermal diffe rentiation gene, repetin (Rptn), exhibiting striking similarity to the genes of the intermediate filament-associated proteins profilaggrin a nd trichohyalin. The repetin gene consists of three exons and two intr ons. The first exon is short and untranslated. The deduced amino acid sequence distributed between exons II and III contains 1130 amino acid s with a calculated molecular mass of 130 kDa and pI of 7.7. The amino terminus exhibits significant homology to the S100 proteins containin g two calcium-binding motifs of the EF-hand type. The remainder coding sequence contains a central segment consisting of 49 tandem repeats o f a 12-amino-acid sequence rich in glutamines. By fluorescence in situ hybridization the repetin gene was localized to chromosome band 3 F1- 2. Expression of repetin mRNA is detectable in the stratified internal epithelia of forestomach and tongue and to a lesser degree in normal skin epidermis, where it is restricted to the differentiated suprabasa l cell layers. Based on its chromosomal localization, its genomic orga nization, and its stage-specific expression during late epidermal diff erentiation, as well as on the structural features of the encoded prot ein, we conclude that the repetin gene represents a novel member of th e ''fused gene'' subgroup of the S100 gene family encoding multifuncti onal epidermal matrix proteins. (C) 1997 Academic Press.