<i>Drosophila</i>Heterochromatin Stabilization Requires the Zinc-Finger Protein Small Ovary

Heterochromatin-mediated repression is essential for controlling the expression of transposons and for coordinated cell type-specific gene regulation. The <i>small ovary</i> (<i>sov</i>) locus was identified in a screen for female-sterile mutations in <i>Drosophila melanogaster</i>, and mutants show dramatic ovarian morphogenesis defects. We show that the null <i>sov</i> phenotype is lethal and map the locus to the uncharacterized gene <i>CG14438</i>, which encodes a nuclear zinc-finger protein that colocalizes with the essential Heterochromatin Protein 1 (HP1a). We demonstrate Sov functions to repress inappropriate gene expression in the ovary, silence transposons, and suppress position-effect variegation in the eye, suggesting a central role in heterochromatin stabilization.