Activation of liver X receptors LXRα (NR1H3) and LXRβ (NR1H2) induces expression of ATP-binding cassette transporter A1 (ABCA1) (Jakobsson T et al. 2009). NR1H2,3 form functional dimers with retinoid X receptors (RXR) that bind to LXR-response elements (LXREs) in the DNA of target genes (Wiebel FF & Gustafsson JA 1997). Nuclear receptor coactivator 1 (NCOA1, also known as SRC1) binds to the ABCA1 gene promoter via oxysterol-induced NR1H3:RXR heterodimer (Huuskonen J et al. 2004). NCOA1 recruits E1A-associated protein p300 (EP300 or p300) leading to a maximal activation of ABCA1 promoter activity (Huuskonen J et al. 2004). EP300 are homologous coactivators capable of binding to the AD1 domain of p160 coactivators such as NCOA1.
EP300, NCOA1 and other members of the p160 coactivator complex contribute to active chromatin structures via coactivator binding activity, acetylation or methylation of histones and other components of the transcription unit (reviewed in Xu J & Li Q 2003; Xu L et al. 2009; Chan HM & La Thangue NB 2001).