IDENTIFICATION IN THE RAT PROLACTIN GENE OF SEQUENCES HOMOLOGOUS TO THE DISTAL PROMOTER OF THE HUMAN PROLACTIN GENE

The goal of the present study was to test the hypothesis that a second , more distal, promoter exists upstream from the rat prolactin (PRL) g ene (rPrl) that is homologous to that identified upstream from the hum an prolactin gene (hPrl). The nucleotide sequence of the rat genome ex tending from 7.4 to 2.5 kb upstream from the proximal rPrl promoter wa s determined, revealing significant sequence homology to the hPrl dist al promoter and its 5'-flanking domain. Using reverse transcription-po lymerase chain reaction, novel rPrl transcripts that originate upstrea m from the proximal rPrl promoter were detected in rat uterus, spleen, pens medulla, anterior pituitary and the GH4Cl pituitary tumor cell l ine. Further characterization of these novel 5'-extended rPrl transcri pts from GH4Cl tells indicated that they were full length, polyadenyla ted and properly spliced. However, data from primer extension (5'-RACE ) experiments strongly suggested that the 5'-extended rPrl transcripts originate, not at the distal promoter-like motif, but at scattered si tes located 60-153 bp upstream from the proximal promoter. Therefore: it appears improbable that the rat sequences homologous to the hPrl di stal promoter comprise a functional promoter. (C) 1998 Elsevier Scienc e B.V. All rights reserved.