Endless: A purine-binding RNA motif that can be expressed in cells

Abstract

It is becoming increasingly clear that nature uses RNAs extensively for regulating vital functions of the cell, and short sequences are frequently used to suppress gene expression. However, controlling the concentration of small molecules intracellularly through designed RNA sequences that fold into ligand-binding structures is difficult. The development of "endless", a triplex-based folding motif that can be expressed in mammalian cells and binds the second messenger 3′,5′-cyclic guanosine monophosphate (cGMP), is described. Invitro, DNA or RNA versions of endless show low micromolar to nanomolar dissociation constants for cGMP. To test its functionality invivo, four endless RNA motifs arranged in tandem were co-expressed with a fluorescent cGMP sensor protein in murine vascular smooth muscle cells. Nitric oxide induced endogenous cGMP signals were suppressed in endless-expressing cells compared to cells expressing a control motif, which suggests that endless can act as a genetically encoded cGMP sink to modulate signal transduction in cells. A sink for a second messenger: A denovo designed RNA motif, termed endless, binds the second messenger 3′,5′-cyclic guanosine monophosphate (cGMP) with low micromolar affinity. The binding pocket of endless does not involve the strand termini, which makes it suitable for expression in cells. There, it suppresses NO-induced cGMP signals, which suggests that it can act as a genetically encoded cGMP sink. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.