Selection of DNA aptamers against rat liver X receptors

Liver X receptors alpha and beta (LXR alpha; LXR beta) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. LXRs play an important role in the reverse cholesterol transport and govern the expression of many of the proteins that are indispensable for the regulation of normal cholesterol levels in the body. SELEX, an in vitro selection technology, was used on a single stranded DNA library harboring a 12 randomized nucleotide sequence in order to isolate aptamers showing affinity for LXR alpha. Enzyme-linked assays and surface plasmon resonance measurements showed that the selected aptamers had strong affinities for LXRa with apparent dissociation constants, K(d)s, in nanomolar range. All clones carried CG-repeats, indicating a probability for a similar manner of binding to LXR alpha. Very high cross-reactivities were observed when testing the aptamers with LXR beta (up to 700%) and RXR alpha (up to 50%). If instead we regard the aptamer sequences as selected against LXR beta, the cross-reactivities decrease considerably, to 17% for LXR alpha and 7% for RXR alpha. Therefore, in the future we are planning to use the obtained aptamers as binders for LXR beta. (C) 2005 Elsevier Inc. All rights reserved.