CLOTTING AND REGULATION OF CORNIFIN-BETA, A NEW MEMBER OF THE CORNIFIN SPR FAMILY - SUPPRESSION BY RETINOIC ACID RECEPTOR-SELECTIVE RETINOIDS/

In this study, we describe the isolation and characterization of a cDN A clone C12 that encodes a new member of the cornifin/small proline-ri ch protein (spr) family, which we have named cornifin beta, C12 encode s a 1.1-kilobase pair mRNA and a 24,3-kDa cytosolic protein with a hig h proline content (19%). Its total amino acid sequence exhibits a 37-6 6% identity while the first 30 amino acids at the amino terminus are 8 7% identical to that of members of the cornifin family, At its carboxy l terminus, cornifin beta contains 21 tandem repeats of an octapeptide , Cornifin beta expression is restricted to several squamous epithelia , It is highly expressed in esophagus, tongue, and oral mucosa but, in contrast to cornifin alpha, is not detectable in the epidermis. Both retinoic acid and a retinoid selective for the nuclear retinoic acid r eceptors were very potent suppressors of cornifin beta expression whil e an analog selective for the nuclear retinoid X receptors was much le ss effective, suggesting that a specific retinoid signaling pathway is involved in this suppression, Cornifin beta can function through some of its Gln residues as an amine acceptor in transglutaminase-catalyze d cross-linking reactions, These results indicate that cornifin beta f unctions as a cross-linked envelope precursor.