Activation of the Promoter of the Orphan Receptor SHP by Orphan Receptors That Bind DNA as Monomers

Yoon-Kwang Lee,Keith L Parker,Hueng-Sik Choi,David D Moore

doi:10.1074/jbc.274.30.20869

Abstract

Small heterodimer partner (SHP) is an orphan nuclear receptor that lacks a conventional DNA binding domain. It interacts with several other members of the nuclear receptor superfamily and inhibits receptor transactivation. In order to characterize the regulation of SHP expression, a number of receptors and other transcription factors were tested for effects on the SHP promoter. Among these, the orphan receptor steroidogenic factor-1 (SF-1) was found to potently transactivate the SHP promoter. Detailed footprinting studies show that the SHP promoter contains at least five SF-1 binding sites, and mutagenesis studies demonstrate each of the three strongest binding sites is required for SF-1 transactivation. SHP is coexpressed with SF-1 in adrenal glands, but is also expressed in tissues that lack SF-1, including liver. However, liver expresses a close relative of SF-1, the orphan fetoprotein transcription factor (FTF), and FTF can also transactivate the SHP promoter. These results suggest that alterations in the levels or activities of SF-1 or FTF could modulate SHP expression in appropriate tissues and thereby affect a variety of receptor dependent signaling pathways.

Highlights

Small heterodimer partner (SHP) is an orphan nuclear receptor that lacks a conventional DNA binding domain
A variety of nuclear hormone receptors and other transcription factors were tested for ability to stimulate the SHP promoter in transient transfection
In Y1 cells, which have been routinely used for studies of steroidogenic factor-1 (SF-1) transactivation [16], SF-1 expression increased SHP promoter activity by approximately 5-fold, whereas the TKluc reporter, which contains the thymidine kinase (TK) promoter from herpes simplex virus, did not respond to SF-1 (Fig. 1A)

Summary

EXPERIMENTAL PROCEDURES

Plasmids—Various reporter constructs for the mouse and human SHP promoters were prepared by insertion of polymerase chain reaction-amplified 5Ј-flanking regions of the two genomic DNAs into a previously described luciferase reporter [14]. Preparation of 5Ј deletion constructs of mouse SHP promoter has been described elsewhere [15]. Point mutations were introduced into the SHP(Ϫ453)luc reporter using

Activation of the SHP Promoter

RESULTS

DISCUSSION