CHARACTERIZATION OF AROMATASE CYTOCHROME-P-450 MESSENGER-RNA IN RAT PERINATAL BRAIN, OVARY, AND A LEYDIG TUMOR-CELL LINE - EVIDENCE FOR THEEXISTENCE OF BRAIN-SPECIFIC AROMATASE TRANSCRIPTS

The conversion of androgens to estrogens is catalyzed by the aromatase cytochrome P-450 (P-450(AROM)) in a variety of tissues and cell types in vertebrates. The manner in which aromatase activity is regulated a ppears to be quite different, even between different tissues of a sing le species. In the current study, we have determined the sequence of t he 5' end of the aromatase mRNA in a rat Leydig tumor cell line, R2C, and in three rat tissues [adult ovary, perinatal amygdala (AmY), and m edial basal hypothalamus-preoptic area (MBH-POA)], each of which shows different patterns of aromatase expression. S-1 nuclease protection a nd primer-extension analyses establish that the site of transcription initiation of the aromatase mRNA present in rat ovary and the rat Leyd ig tumor cell line R2C is located approximately 97 nucleotides upstrea m from the initiator methionine. By contrast, although aromatase mRNA was detected in S-1 nuclease protection experiments using a probe deri ved from the aromatase open-reading frame, transcripts initiating at t his site were absent from RNA samples prepared from perinatal rat AMY and MBH-POA tissue. S-1 mapping and sequencing of the 5' end of AMY an d MBH-POA aromatase cDNAs indicate that the aromatase mRNA transcripts present in these rat neural tissues from perinatal animals contain a distinctive 5' terminus and are derived from a different promoter.