POSSIBLE ROLE OF VARIANT RNA TRANSCRIPTS IN THE REGULATION OF EPIDERMAL GROWTH-FACTOR RECEPTOR EXPRESSION IN HUMAN PLACENTA

Epidermal growth factor receptor (EGFR) plays an important role in gro wth and differentiation. The human placenta expresses high levels of t he receptor. In the placenta, as in many other human tissues, EGFR is encoded by two RNA transcripts of 5.8 kb and 10.5 kb. The placenta als o expresses a putative truncated EGFR transcript of 1.8 kb, which enco des only the ligand binding domain of the receptor. The etiology and r ole of these variant EGFR transcripts is unknown. Using the human plac enta as a model to study this area, we report 1) the relationships amo ng these transcripts suggest that the induction of alternate pathways of EGFR RNA processing is involved in their etiologies; 2) the 10.5 kb transcript may be the principal transcript involved in determining th e level of the protein receptor; and 3) the isolation of a soluble pro tein with characteristics consistent with a translational product corr esponding to the 1.8 kb transcript, which may act in regulating the ac tivity of EGFR. Together these results suggest that alternate processi ng of EGFR RNA into variant transcripts may represent a novel mechanis m involved in the regulation of the receptor protein. (C) 1995 Wiley-L iss, Inc.