DNase I hypersensitivity analysis of non-pituitary human prolactin gene expression

The expression of non-pituitary human PRL is initiated at a unique 5' untra nslated exon located similar to 5.7 kb upstream of the pituitary-specific t ranscriptional start site. Unlike pituitary PRL expression, transcriptional regulation from the upstream promoter does not rely on the POU-homeodomain protein Pit-1. We have used DNase I mapping of chromatin from PRL-producin g and non-producing human lymphoblastoid cell lines to identify hypersensit ive sites unique to the PRL expressing phenotype. Analysis of 22 kb of 5' f lanking DNA revealed DNase I hypersensitive sites in intron A-1 separating the pituitary from non-pituitary specific transcription start site which we re only detected in the PRL-producing cell line. Transient transfection sho wed strong transcriptional activity directed by this region only in the: an tisense orientation and in a non cell-type specific manner. Transfection ex periments with deletion mutants of 5259 bp of the non-pituitary PRL promote r region also revealed promoter activity not restricted to the PRL expressi ng phenotype. These data suggest that non-pituitary PRL gene expression may be regulated by elements located in intron A-1 and that recapitulation of cell-specific expression requires a unique cellular context and chromatin a ssembly. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights res erved.