Anti-Rex Aptamers as RNA Mimics of the Rex-Binding Element

摘要

RNA molecules that bind tightly and specifically to a Rex fusion protein havebeen isolated from a conformationally constrained pool of random sequence RNAs. These RNAs effectively mimic a number of features of the wild-type Rex-binding element (XBE). The aptamers compete with the wild-type Rex-binding element for binding to Rex in vitro. The highest-affinity aptamers can specifically bind the Rex ARM, and do not recognize the functionally analogous Rev protein or its ARM. The anti-Rex aptamers can also functionally substitute for the Rex-binding element in vivo, a result which supports a previously proposed model for mRNA transport in which the viral genome serves as a passive platform for assembling and co-opting the cellular transport apparatus. Characteristic sequence and structural motifs found in some of the anti-Rex aptamers may provide insights into the ability of Rex to bind the Rev-responsive element. Overall, these studies suggest that anti-Rex aptamers may serve as effective RNA decoys of Rex.