- A short proximal promoter and the distal hepatic control region-1 (HCR-1) contribute to the liver specificity of the human apolipoprotein C-II gene. Hepatic enhancement by HCR-1 requires two proximal hormone response elements which have different binding specificities for orphan receptors HNF-4, ARP-1, and EAR-2. Vorgia, P., Zannis, V.I., Kardassis, D. J. Biol. Chem. (1998)