PITUITARY-SPECIFIC TRANSCRIPTION FACTOR (PIT-1) BINDING-SITE IN THE HUMAN RENIN GENE 5'-FLANKING DNA STIMULATES PROMOTER ACTIVITY IN PLACENTAL CELL PRIMARY CULTURES AND PITUITARY LACTOSOMATOTROPIC CELL-LINES

Renin gene expression is limited to a number of specific tissues, incl uding the kidney, adrenal glands, reproductive organs (of particular r elevance to this study, the placenta), and the pituitary gland. In the present study, we investigated the human renin (hRen) 5'-flanking DNA sequences required to drive the expression of a luciferase reporter g ene in placental and pituitary cells and in two cell lines, 293 and JE G-3, which have been proposed as model systems with which to study tra nscriptional regulation of renin genes. The activities of specific seq uences in the hRen 5'-flanking DNA sequences in human placental cell p rimary cultures were very similar to those that we previously reported in pituitary cells, suggesting the involvement of common promoter ele ments and related transcription factors. Accordingly, the binding site for the pituitary-specific transcription factor (Pit-1) was the major determinant of renin promoter activity in both pituitary and placenta l cells. Gel mobility shift analysis showed a placental nuclear factor with a gel mobility different from that of Pit-1. However, Northern b lot analysis failed to demonstrate abundant Pit-1-related mRNAs in ren in-expressing cultures of chorionic and decidual cells, suggesting tha t the placental factor is not closely related to Pit-1. Although a fac tor from 293 cells also bound to the Pit-1 site, it had gel mobility s hift characteristics different from Pit-1 and the placental factor. Mo reover, the low promoter activity in 293 cells was independent of this site or, indeed, of sequences upstream from the TATA box. In JEG-3 ce lls, renin 5'-flanking DNA sequences showed virtually no transcription al activity. Taken together, these data suggest that common cis-acting sequences direct renin gene expression to pituitary and placental cel ls and that the activity of these sequences is dependent on the presen ce of transcription factors specific to these cells. Our studies also indicate that 293 and JEG-3 cell lines may not be appropriate for the study of renin gene expression.