Targeting and Anchoring Tudor in the Pole Plasm of the Drosophila Oocyte

Abstract

BackgroundGermline formation is a highly regulated process in all organisms. In Drosophila embryos germ cells are specified by the pole plasm, a specialized cytoplasmic region containing polar granules. Components of these granules are also present in the perinuclear ring surrounding nurse cells, the nuage. Two such molecules are the Vasa and Tudor proteins. How Tudor localizes and is maintained in the pole plasm is, however, not known.Methodology/Principal FindingsHere, the process of Tudor localization in nuage and pole plasm was analyzed. The initial positioning of Tudor at the posterior pole of stage 9 oocytes was found to occur in the absence of a structurally detectable nuage. However, in mutants for genes encoding components of the nuage, including vasa, aubergine, maelstrom, and krimper, Tudor was detached from the posterior cortex in stage 10 oocytes, suggesting a prior passage in the nuage for its stability in the pole plasm. Further studies indicated that Valois, which was previously shown to bind in vitro to Tudor, mediates the localization of Tudor in the pole plasm by physically interacting with Oskar, the polar granule organizer. An association between Tudor and Vasa mediated by RNA was also detected in ovarian extracts.Conclusions/SignificanceThe present data challenge the view that the assembly of the polar granules occurs in a stepwise and hierarchical manner and, consequently, a revised model of polar granule assembly is proposed. In this model Oskar recruits two downstream components of the polar granules, Vasa and Tudor, independently from each other: Vasa directly interacts with Oskar while Valois mediates the recruitment of Tudor by interacting with Oskar and Tudor.

Structure of Drosophila Oskar reveals a novel RNA binding protein

“…Oskar protein translation is repressed during transport by the RNA-binding protein Bruno and this repression is released by the binding of activators, such as Orb, once the RNA reaches the posterior pole (7)(8)(9)(10)(11). Oskar organizes germ plasm by recruiting other proteins, such as Vasa, Tudor, and Aubergine (12)(13)(14)(15). An important function of germ plasm is the localization of 50-200 germ plasm-associated RNAs (16,17).…”

Germ Plasm Biogenesis—An Oskar-Centric Perspective

“…A number of interaction partners for Short-Oskar have been identified. These include Vasa, an ATP dependent helicase, Valois, a methyltransferase associated WD-repeat protein, and Lasp (Anne, 2010; Breitwieser et al, 1996; Jeske et al, 2015; Suyama et al, 2009). Recently, two studies provided insight into the function of Oskar by determining the structure of two domains in Oskar (Fig 2F): a domain at the very N-terminus of short-Oskar (139–240), which was initially identified by bioinformatics and termed LOTUS domain due to its presence in Limkain, Oskar and Tudor containing proteins 5 and 7; and the C-terminal “OSK” domain, which resembles a SGNH hydrolase or lipase domain found in mammalian platelet-activating factor acetylhydrolase (PAF-AH) and GDSL-like lipases (Jeske et al, 2015; Yang et al, 2015).…”

The piRNA Pathway Guards the Germline Genome Against Transposable Elements

“…4.5b; Table 4.1). The enrichment of AUB at the pole plasm depends on sDMA modifications that allow it to bind Tudor, which itself is anchored to the pole plasm by the PRMT5 methylosome complex and the body-patterning-associated factor Oskar (Anne and Mechler 2005; Anne 2010; Arkov et al 2006; Anne et al 2007; Thomson and Lasko 2004; Kugler and Lasko 2009; Liang et al 1994). …”