A possible expansion of the VISTA enhancer database

The VISTA enhancer database is a valuable resource for evaluating predicted enhancers in humans and mice. In addition to thousands of validated positive regions (VPRs) in the human and mouse genomes, the database also contains similar numbers of validated negative regions (VNRs). We have previously shown that the VPRs are on average half as long as predicted overlapping enhancers that are highly conserved, and hypothesize that the VPRs might be truncated forms of long bona fide enhancers. Here, we show that like the VPRs, the VNRs also are under strongly evolutionary constraints and overlap predicted enhancers in the genomes. Moreover, the VNRs are also on average half as long as predicted overlapping enhancers that are highly conserved. Thus, we hypothesize that like the VPRs, the VPRs might also be truncated forms of long bona fide enhancers.