A selective screen reveals discrete functional domains in Drosophila Nanos

The Drosophila protein Nanos encodes an evolutionarily conserved protein wi th two zinc finger motifs. In the embryo, Nanos protein function is require d for establishment of the anterior-posterior body pattern and for the migr ation of primordial germ cells. During oogenesis, Nanos protein is involved in the establishment and maintenance of germ-line stem cells and the diffe rentiation of oocyte precursor cells. To establish proper embryonic pattern ing, Nanos acts as a translational regulator of hunchback RNA. Nanos' targe ts for germ cell migration and development are not known. Were, we describe a selective genetic screen aimed at isolating new nanos alleles. The molec ular and genetic analysis of 68 new alleles has allowed us to identify amin o acids critical for nanos function. This analysis shows that the CCHC moti fs, which coordinate two metal ions, are essential for all known functions of Nanos protein. Furthermore, a region C-terminal to the zinc fingers seem s to constitute a novel functional domain within the Nanos protein. This "t ail region" of Nanos is required for abdomen formation and germ cell migrat ion, but not for oogenesis.