P450AROM GENE-EXPRESSION IN PERIPHERAL-BLOOD LYMPHOCYTES - IDENTIFICATION OF A CRYPTIC SPLICE-SITE FOR EXON-1 AFTER EPSTEIN-BARR-VIRUS TRANSFORMATION

The human aromatase gene (P450arom) is widely expressed, albeit in a t issue-specific manner. In the present study, we measured aromatase act ivity and investigated the transcribed and translated products of the P450arom gene before and after Epstein-Barr virus (EBV) transformation in peripheral blood lymphocytes (PBLs) from normal individuals. Aroma tase activity was determined by [H-3]-Delta(4)-androstenedione (A) to [H-3]-estrone (El) conversion. Cellular total RNA and protein lysates were subjected to RT-PCR and Western analysis, respectively. Rapid amp lification of cDNA ends (RACE) was used for the detection of novel 5'- untranslated ends of the P450arom mRNA, which were subsequently sequen ced and compared to the known transcripts of this gene. In untransform ed PBLs, two known variants of exon 1 of the P450arom gene were expres sed, corresponding to promoters PI.3 and PII, or Ic and Id, respective ly. In EBV-transformed PBLs, a cryptic splice site was revealed and a new 5'-untranslated product was found. RNase protection assay confirme d that this splice variant is not a RACE artifact. The 53 K P450arom p rotein was detectable in PBLs both before and after EBV transformation . We conclude that (i) the P450arom mRNA is present in human PBLs and (ii) EBV transformation of the latter leads to novel alternative splic ing of the 5' end of this gene. (C) 1998 Elsevier Science Ltd. All rig hts reserved.