Estrogen receptor-alpha (ER-α) suppresses expression of its variant ER-α36

Recently, we identified and cloned a membrane-based estrogen receptor (ER), ER-α36, which is transcribed from a previously unidentified promoter in the first intron of the original ER-α gene. We cloned the 5′ flanking region of ER-α36 and found the cloned DNA sequence possessed strong promoter activity. A single transcription initiation site was mapped and a number of putative regulatory elements for various transcription factors such as the Wilms’ tumor suppressor, WT1 and estrogen receptor (ER) were identified in this region. Transient co-transfection experiments further demonstrated that ER-α suppresses ER-α36 promoter activity in an estrogen-independent manner, which can be released by ER-α36 itself.