Anti-androgenic properties of Compound A, an analog of a non- steroidal plant compound T.M. Tanner a , G. Verrijdt b , W. Rombauts b , A. Louw a , J.P. Hapgood a , F. Claessens b, * a Department of Biochemistry, University of Stellenbosch, 7600 Stellenbosch, South Africa b Division of Biochemistry, Faculty of Medicine, Campus Gasthuisberg, Catholic University of Leuven, Herestraat 49, 3000 Leuven, Belgium Received 9 April 2002; accepted 28 October 2002 Abstract We investigated the interactions between Compound A (CpdA), an analog of a hydroxyphenyl aziridine precursor found in an African shrub, and the androgen receptor (AR). CpdA represses androgen-induced activation of both specific and non-specific androgen DNA response elements. While a similar effect was obtained for the progesterone receptor (PR) via a non-specific hormone response element, CpdA had no effect on the actions of the glucocorticoid and mineralocorticoid receptors. CpdA represses the ligand-dependent interaction between the NH 2 - and COOH-terminal domains of the AR, similar to well-characterised anti-androgens. CpdA also interferes with the interaction of steroid receptor co-activator 1 (SRC1) with the activation domain AF2 but not with AF1. However, CpdA does not compete with androgen for binding to the AR. These results demonstrate that CpdA elicits anti-androgenic actions by a mechanism other than competitive binding for the AR. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Androgen receptor; Anti-androgen; Aziridine precursor; N/C-interaction 1. Introduction Compound A (CpdA), 2-(4-acetoxyphenyl)-2-chloro- N -methyl-ethylammonium chloride, is a non-steroidal compound that was developed as a stable analog (Fig. 1) of a highly labile hydroxyphenyl aziridine precursor (Louw et al., 1997) found in the African shrub, Salsola tuberculatiformis Botsch. CpdA can interact with ster- oid-binding proteins such as steroidogenic enzymes (Louw et al., 2000a) and plasma steroid-binding globu- lins (Louw et al., 2000b). We were thus prompted to investigate the possible interactions between CpdA and other steroid-binding proteins, in particular the steroid receptors. The steroid receptors form a subfamily of the nuclear receptor superfamily, a large group of ligand-dependent transcription factors. The steroid receptors include the androgen receptor (AR), estrogen receptor, glucocorti- coid receptor (GR), mineralocorticoid receptor (MR) and progesterone receptor (PR). In general, the inactive steroid receptors reside predominantly in the cytosol. The steroid hormones bind to these receptors, which are then activated. After activation, the hormone receptor- complex translocates to the cell nucleus where it binds to specific DNA sequences, called response elements and subsequently regulates gene expression (Evans, 1988; Beato, 1989). There is a high level of similarity between the members of the nuclear receptor superfamily, where the arrangement of the different domains is essentially the same for all the members. This arrangement involves the highly variable NH 2 -terminal domain (NTD), fol- lowed by the highly conserved and centrally located DNA-binding domain (DBD) through which the inter- actions with the response elements are mediated. The COOH-terminal (C-terminal) domain that is also con- served between members of the family contains the ligand binding domain (LBD), and areas involved in stabilisation of homodimerisation as well as orchestra- tion of interactions with coregulators (Moras and * Corresponding author. Tel.:  /32-16-34-5770; fax:  /32-16-34- 5995. E-mail address: frank.claessens@med.kuleuven.ac.be (F. Claessens). Molecular and Cellular Endocrinology 201 (2003) 155  /164 www.elsevier.com/locate/mce 0303-7207/03/$ - see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. doi:10.1016/S0303-7207(02)00411-2