The invention provides polynucleotide constructs for the regulation of gene expression by aptamer-based modulation of U1 small nuclear ribonucleoprotein (snRNP)-mediated suppression of polyadenylation and methods of using the constructs to regulate gene expression in response to the presence or absence of a ligand that binds the aptamer. The polynucleotide construct contains a U1 binding site in the context of a riboswitch comprising an effector region and an aptamer such that when the aptamer binds a ligand, target gene expression occurs.
