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.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.42079 |
| Date | January 1996 |
| Creators | Liang, Lu. |
| Contributors | Lasko, P. F. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001567280, proquestno: NQ30321, Theses scanned by UMI/ProQuest. |
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