ABSTRACT
A. Retinoic Acid Receptors (RARs) 1. Three RAR Genes Three types of retinoic acid receptors (RARa, f3, andy) which bind both all-trans-(T-RA) and 9-cis-(9C-RA) retinoic acid (see below) have been uncovered by eDNA cloning in both human (h) and mouse (m). hRARa (the hRARa1 isoform; see below) was initially identified by low-stringency screening for cDNAs encoding steroid receptor-like molecules (12,13); hRARf3 (the hRARf32 isoform, see below), was first found as a gene (hap) into which integration of the hepatitis B virus had occurred in a hepatocarcinoma (14-17). mRARa and f3 cDNAs were subsequently isolated from a mouse eDNA library by cross-hybridization with the human probes (18). The same screening yielded a third type of receptor, mRARy (the mRARy1 isoform; see below), which was also identified in human (19,20).
