Exon 3 of the alpha folate receptor gene contains a 5 ' splice site which confers enhanced ovarian carcinoma specific expression

The human folate receptor (FR) is overexpressed in ovarian carcinoma. FR tr anscripts are heterogeneous due to the use of two promoters, P1 and P4, and alternative splicing of exon 3. RNase protection assay and RT-PCR revealed higher levels of the transcripts that include exon 3 in lines and specimen s from ovarian carcinoma. A P1-chloramphenicol acetyltransferase (CAT) cons truct containing exon 3 demonstrated efficient reporter expression only in ovarian carcinoma. 5' and 3' deleted variants of the P1-CAT construct were analyzed by RT-PCR of the exogenous transcripts and reporter activity. A 5' splice site and 35 bp downstream intronic region of exon 3 appeared to reg ulate enhanced FR expression in ovarian carcinoma. (C) 2001 Published by El sevier Science B.V. on behalf of the Federation of European Biochemical Soc ieties.