C. Francastel et al., A functional enhancer suppresses silencing of a transgene and prevents itslocalization close to centromeric heterochromatin, CELL, 99(3), 1999, pp. 259-269
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.