A functional enhancer suppresses silencing of a transgene and prevents itslocalization close to centromeric heterochromatin

To explore the mechanism by which enhancers maintain gene expression, we ha ve assessed the ability of an enhancer and derivative mutants to influence silencing and nuclear location of a transgene. Using site-specific recombin ation to place different constructs at the same integration sites, we find that disruption of Gore enhancer motifs impairs the enhancer's ability to s uppress silencing. FISH analysis reveals that active transgenes linked to a functional enhancer localize away from centromeres. However, enhancer muta tions that result in increased rates of transgene silencing fail to localiz e the transgene away from centromeric heterochromatin, even when the transg ene is in an active state. These mutations thus dissociate transcriptional activity and subnuclear location. Together, our results suggest that the fu nctional enhancer antagonizes gene silencing by preventing localization of a gene near centromeric heterochromatin.