SUNY at Albany
June 19-23, 2001
Sexual Dimorphism in Diverse Metazoans is Regulated by a Novel Class of Intertwined Zinc Fingers: NMR and Crystallographic Studies of the Doublesex DM Domain
Sex determination is regulated by diverse pathways. Although upstream signals vary, a cysteine-rich DNA-binding domain (the DM motif) is conserved within downstream transcription factors of Drosophila melanogaster (Doublesex) and Caenorhabditis elegans (MAB-3). Vertebrate DM genes have likewise been identified and, remarkably, are associated with human sex reversal (46, XY gonadal dysgenesis). Here, we investigate the structure of the Doublesex domain by a combination of NMR spectroscopy, X-ray crystallography and mutagenesis. The free domain contains a novel Zn module and disordered tail. The module consists of intertwined CCHC and HCCC Zn-binding sites; the tail functions as a nascent recognition alpha helix. Mutations in either Zn-binding site or tail can lead to an intersex phenotype. The motif binds in the DNA minor-groove without sharp DNA bending. Progress toward the co-crystal structure of a DSX dimer bound to a specific DNA site will be presented. The molecular features of the DSX Zn module, unusual among Zn fingers and Zn modules, underlie the organization of a Drosophila enhancer that integrates sex- and tissue-specific signals. Complementary NMR and crystal structures will provide a foundation for analysis of DM mutations affecting sexual dimorphism and courtship behavior.
Lingyang Zhu, Narendra Narayana, Uma Narendra, Biaoru Li & Michael A. Weiss.
Department of Biochemistry, Case Western Reserve School
of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-4935.