Figure 5. Oskar (Osk) interacts with the helicase superfamily C-terminal domain (HELICc) of Drosophila Vasa (DmVas) in vivo and in vitro.

(A–L) Localisation analyses of (A–D) green fluorescent protein (GFP)-DmVas, (E–H) GFP-Vas^{460–621/HELICc}, and (I–L) GFP-SgVas^HELICc were performed in egg chambers at Stage 10 by immunostaining with the anti-GFP antibody. Genetic backgrounds: (A,E,I) Wild-type; (B,F,J) osk mutant with the genotype osk⁵⁴/Df(3R)pXT103; (C,G,K) vls null mutant with the genotype Df(2L)Pr2b,P[barren+]/Df(2L)be408; (D,H,L) tud mutant with the genotype tud^tux46/Df(2R)PF1. All the 3 GFP-tagged Vas proteins could be localised to the posterior germ plasm, except in the osk mutant background. (M,N) Yeast two-hybrid analysis performed using the β-galactosidase colony lift filter assay. (M) None of the singly transformed ‘bait’ and ‘prey’ plasmids could induce the expression of the lacZ reporter. (N) Osk could interact with full-length DmVas and DmVas^{460–621/HELICc}. (O–T) Stage-10 egg chambers were stained with the anti-GFP (green) and anti-Osk antibodies (red). (Q,T) Merged images. (O–Q) GFP-DmVas^{460–621/HELICc} was colocalised with Osk in the germ plasm. (R–T) In the egg chambers coexpressing the GFP-DmVas^{460–621/HELICc} and osk-bcd 3′UTR transcripts, the GFP-DmVas^{460–621/HELICc} was colocalised with Osk in the anterior and posterior poles of the oocyte. In the panels with egg chambers (A–L,O–T), anterior is to the left and posterior is to the right. The DmVas^{460–621/HELICc} is abbreviated as DmVas^460–621 in all the panels. Scale bars, 25 μm.