Mechanistic insights into the link between a polymorphism of the 3'UTR of the SLC7A1 gene and hypertension.

We previously identified the polymorphism ss52051869 in the 3'UTR of human SLC7A1, and demonstrated that it might participate in the apparent link between altered endothelial function, decreased L-arginine and nitric oxide (NO) metabolism, and a genetic predisposition to essential hypertension. Here, we demonstrate that the major allele contains a consensus sequence for the transcription factor SP1 and binds to SP1, in contrast, the minor allele fails to bind to SP1. Resequencing of the entire SLC7A1 coding sequence failed to find other informative polymorphisms, indicating that ss52051869 plays a key role in the biochemical and clinical association. In conjunction, the short and long variants of the 3'UTR of SLC7A1 contain three and four potential microRNA-122 (miR-122) binding sites, respectively. We found that the minor allele is more frequently associated with SLC7A1 bearing a long 3'UTR, while the major allele is more likely to accompany a short 3'UTR only (P=0.034). As such, reporter genes containing the long 3'UTR from SLC7A1 show much less gene expression than those containing short 3'UTR from SLC7A1, regardless of their allele status (P<0.01), suggesting that an alternative polyadenylation event and/or miRNA-122 binding sites may also play a role in controlling gene expression. It is therefore possible that binding of miR-122 to the 3'UTR may cause the depression of gene expression, contributing to the lesser level of SLC7A1 and the endothelial dysfunction seen in hypertensive subjects. Taken together, these data provide novel insights into the mechanism by which ss52051869 influences SLC7A1 gene expression.