Nuclear receptors (NR) activate transcription by interacting with several different coactivator complexes, primarily via LXXLL motifs (NR boxes) of the coactivator that bind a common region in the ligand binding domain of nuclear receptors (activation function-2, AF-2) in a ligand-dependent fashion. However, how nuclear receptors distinguish between different sets of coactivators remains a mystery, as does the mechanism by which orphan receptors such as hepatocyte nuclear factor 4␣ (HNF4␣)

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... ate transcription. In this study, we show that HNF4␣ interacts with a complex containing vitamin D receptor (VDR)-interacting proteins (DRIPs) in the absence of exogenously added ligand. However, whereas a full-length DRIP205 construct enhanced the activation by HNF4␣ in vivo, it did not interact well with the HNF4␣ ligand binding domain in vitro. In investigating this dis-0888-8809/02/$15.00/0 Molecular Endocrinology 16 (7) :1502-1510 Printed in U.S.A.