No description available.

No description available.

No description available.

The Drosophila melanogaster gene vasa is known to be necessary for the establishment of a functional pole plasm, as well as for the completion of oogenesis. To further elucidate its role, we have created a null mutation of the vasa gene and examined vasa-null ovaries for defects. Analysis of these ovaries has revealed that vasa is involved in various aspects of oogenesis, including the growth of germ-line cysts, oocyte differentiation, anterior-posterior egg chamber patterning, and dorsal-ventral follicle patterning. In addition, vasa-null oocytes fail to show efficient accumulation of various localized RNAs, such as Bicaudal-C, Bicaudal-D, egl, enc, orb, oskar , and nanos, but still show accumulation of gurken RNA. Interestingly, the accumulation of GURKEN protein in the oocyte is severely reduced, and that of BICAUDAL-C is substantially decreased in null mutants. These results suggest a possible role for vasa in activating translation of targeted RNAs during oogenesis.

Pole plasm in Drosophila melanogaster, through the posteriorly localized determinant nanos, controls the formation of the abdominal segments and, through an unknown mechanism, controls the formation of the germline. oskor, vasa, and tudor are three critical genes in the pole plasm assembly pathway and their gene products, oskar RNA, Vasa protein and Tudor protein are localized in the pole plasm in a precise order. The localization of oskar and nanos mRNAs is closely related to their translational activation. We provide evidence here by in vitro biochemical assays that Vasa protein is an ATP-dependent RNA helicase, an ATPase and an RNA-binding protein, as was predicted from its sequence similarity to mammalian translation initiation factor eIF-4A. The enzymatic activities of Vasa protein are important for its function, but the initial localization of Vasa protein to the pole plasm is independent of its RNA helicase and RNA-binding activities. Further, we cloned Bruno, a Xenopus etr-1 homologue with three ribonucleoprotein-recognition-motifs (RRM), by far-western screening using Vasa protein as bait. Bruno is the product of the gene arrest, which was cloned independently by Webster and Macdonald at Stanford University. The localization of Bruno protein in S1-10 oocytes is similar to that of oskar and gurken RNAs. This is significant as both oskar and gurken RNAs contain Bruno-response-elements at their 3$ sp prime$UTRs. Bruno is mislocalized in vasa mutant ovaries, suggesting that the localization of Bruno protein requires Vasa function. As a translational activator of oskar and nanos RNAs and a regulator of Bruno protein. the participation and the importance of Vasa protein in pole plasm assembly and function is obvious. Whether Vasa acts directly or indirectly to activate translation of specific mRNAs will require further examination.

No description available.

No description available.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1983. / Bibliography: leaves 283-290. / Microfiche. / xix, 290 leaves, bound ill. 29 cm

Thesis (Ph. D.)--University of Hawaii at Manoa, 1996. / Includes bibliographical references (leaves 159-175). / Microfiche. / xv, 175 leaves, bound ill. 29 cm

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1968. / Bibliography: leaf 82. / ix, 82 l tables