The eyegone (eyg) gene encodes Eyg, a transcription factor of the Pax family 
with multiple roles during Drosophila development. Although Eyg has been shown 
to act as a repressor, nothing is known about the mechanism by which it 
represses its target genes. Here, we show that Eyg forms a protein complex with 
heterochromatin protein 1a (HP1a). Both proteins bind to the same chromatin 
regions on polytene chromosomes and act cooperatively to suppress variegation 
and mediate gene silencing. In addition, Eyg binds to a wingless (wg) enhancer 
region, recruiting HP1a to assemble a closed, heterochromatin-like conformation 
that represses transcription of the wg gene. We describe here the evidence that 
suggests that Eyg, encoded by eyegone (eyg), represses wingless (wg) during eye 
development by association with HP1a. We show that Eyg forms a protein complex 
with HP1a and both proteins colocalize on salivary gland polytene chromosomes. 
Using position effect variegation (PEV) experiments, we demonstrated that eyg 
has a dose-dependent effect on heterochromatin gene silencing and identified a 
genetic interaction with HP1a in this process. We further demonstrated that HP1a 
binds to the same wg enhancer element as Eyg. DNase I sensitivity assays 
indicated that this enhancer region has a closed heterochromatin-like 
conformation, which becomes open in eyg mutants. In these mutants, much less 
HP1a binds to the wg enhancer region, as shown by ChIP experiments. Furthermore, 
as previously described for Eyg, a reduction in the amount of HP1a in the eye 
imaginal disc derepresses wg. Together, our results suggest a model in which Eyg 
specifically binds to the wg enhancer region, recruiting HP1a to that site. The 
recruitment of HP1a prevents transcription by favoring a closed, 
heterochromatin-like structure. Thus, for the first time, we show that HP1a 
plays a direct role in the repression of a developmentally regulated gene, wg, 
during Drosophila eye development.