RETINOIC ACID - IDENTIFICATION OF SPECIFIC RECEPTORS THROUGH WHICH ITMAY MEDIATE TRANSCRIPTIONAL REGULATION OF FIBRONECTIN GENE IN BOVINE LENS EPITHELIAL-CELLS

To elucidate in detail the regulatory mechanisms by which the fibronec tin mRNA and protein are altered by all-trans retinoic acid (RA) in bo vine lens epithelial (LE) cells, we have investigated the transcriptio n mechanism and the occurrence of nuclear receptors for RA in the nucl ei of cultured LE cells. The rate of transcription of fibronectin (FN) mRNA increased by 130% in response to RA. The RA receptors in nuclear extracts prepared from LE cells show specific all-trans [H-3]-RA bind ing sites. Saturation binding of all-trans RA to these receptors and t he Scatchard plot analyses of the binding data yielded an apparent dis sociation constant (K-d) of about 12 nM and B-max of about 48 pmoles/m g protein. Bovine retinoic acid receptors (RARs) have not been reporte d previously. Our results demonstrate for the first time that RA regul ates FN expression and that regulation is at the transcriptional level in LE cells. Thus, retinoids may have an important role in the functi onal adhesion of epithelium to the lens capsule. (C) 1996 Academic Pre ss Limited