Gene transfer and in vivo promoter analysis of the rat progesterone receptor using a herpes simplex virus viral vector

Abstract

The progesterone receptor (PR) gene is expressed in cells of the anterior pituitary and hypothalamus, and PR levels are regulated by estrogen (E) in a tissue-specific fashion. To demonstrate that E induces transcription via the PR promoter, and to identify sequences within the PR promoter responsible for tissue-specific and hormonal regulation, we have utilized a defective herpes simplex virus vector for direct gene transfer into the rat pituitary and brain. We designed a viral amplicon expressing the β-galactosidase gene under the regulation of a 2.1-kb PR promoter fragment to create a defective viral vector for gene transfer into the brain. Following injection of this vector into the pituitary and brain, its pattern of expression and ability to respond to estradiol 3-benzoate (EB) were examined. In the pituitary, lacZ activity was observed in cells of the anterior lobe (AL). However, no activity was seen in the neurointermediate lobe (NIL), demonstrating tissue specific transcriptional regulation. A ∼sixfold increase in cells demonstrating β-galactosidase activity was observed in the AL following treatment with EB. Likewise, injection of defective viral vector into the hypothalamus followed by treatment with EB resulted in a ∼eightfold increase in cells demonstrating β-galactosidase activity including the very cell groups responsible for EB-dependent reproductive behavior. In contrast, no vector dependent activity was observed in the caudate nucleus, a tissue with no endogenous expression of PR, despite polymerase chain reaction evidence demonstrating the presence of the vector in this tissue. These results demonstrate that the 2.1-kb PR promoter fragment contains the sequence information required for correct tissue and hormonal regulation of PR.