CDNA CLONING AND CHARACTERIZATION OF SCIELLIN, A LIM DOMAIN PROTEIN OF THE KERATINOCYTE CORNIFIED ENVELOPE

Sciellin is a precursor of the cornified envelopes of mammalian kerati nizing tissues. We have cloned the cDNA encoding sciellin by screening a human keratinocyte expression library with a sciellin-specific mono clonal antibody. The composite cDNA of 2.35 kilobase pairs encodes a p rotein of 75.3 kDa with a pi of 10.09, The translated sequence has a c entral domain containing 16 repeats of 20 amino acids each that is ric h in Gin and Lys residues, which are potential transglutaminase substr ates, and a carboxyl domain, which contains a single LIM motif, Sciell in cDNA probes hybridize to bands of 3.4 and 4.4 kilobase pairs on Nor thern blots of cultured human keratinocyte RNA. The gene was mapped to human chromosome band 13q22 by fluorescence in situ hybridization, Ra diation hybrid mapping demonstrated that sciellin is linked to the seq uence tagged site marker WI-457 with a logarithm of the odds score of 7.77, In situ hybridization of human foreskin tissue sections demonstr ated that sciellin is expressed in the stratum granulosum, Immunofluor escent staining with a polyclonal rabbit antibody made to a recombinan t sciellin protein showed peripheral cytoplasmic localization in the u pper cell. layers of epidermis and in stratified squamous epithelia su ch as the oral cavity, esophagus, and vagina. Simple and columnar epit helia, with the exception of the amnion, showed no reaction.