For the wild-type oocytes, the ratios were 1.54, 1.79, 1.83, and 2.00. regions can be accomplished by a coordinated program of mRNA localization and translational control. These mechanisms are used prominently during oogenesis in mRNA; these include Squid (Hrp40), Hrp48 (also known as Hrb27C), Bruno (Bru), Vasa, and Otu (8, 9, 13, 31, 41, 45, 49). Each of these proteins is also required for correct expression of (11, 14, 20, 30, 32, 40, 44, 47, 51), revealing substantial similarities in the control of and mRNAs. Mutants defective for Sqd, Hrp48, and Otu have a common mRNA localization defect (9). Normally, mRNA is transiently localized to the anterior of the oocyte at stage 8 of oogenesis and then becomes restricted to the dorsal side of the anterior. In the mutants, mRNA persists along the anterior and fails to localize dorsally. Because localization of mRNA has been suggested to result from two vectorial movementsone toward the anterior and a second directed dorsally (19)these genes could act specifically in the second movement. Sqd and Hrp48 have also been implicated in translational regulation and act to limit the translation of mRNA to the fraction of the mRNA that is properly localized at the dorsal side of the oocyte (9, 31). The mechanistic details of how these proteins contribute to localization and translational control remain to be determined, but KDELC1 antibody it does appear that they function as part of a regulatory RNP complex, Itraconazole (Sporanox) since Hrp48 interacts physically with both Sqd and Otu (9). Two components of the complex, Sqd and Hrp48, have been suggested to assemble with the mRNAs in the nucleus and associate with other factors in the cytoplasm (22-24, 31). It is likely that additional members of this complex have not yet been identified. One candidate for another regulatory factor is Imp, the homolog of a family of proteins that act in posttranscriptional regulation in a variety of animals (34, 50). One of the founding members of the family, ZBP-1, binds to a localization element in the chicken beta-actin mRNA (15) and appears to direct localization to the leading edge of embryonic fibroblasts (7). Another founding member, the Vg1RBP/VERA protein, binds to signals directing localization of Vg1 and VegT mRNAs to the vegetal pole of the oocyte (4, 5, 10, 16). Mammalian homologs, the Imp proteins, have been suggested to act in mRNA localization (36), mRNA stability Itraconazole (Sporanox) (6), and translational regulation (28). A recent report examined the RNA binding properties of Imp protein, focusing specifically on the mRNA and its possible regulation by Imp (26). Although mutation of candidate Imp binding sites in the mRNA did block accumulation of Osk protein, loss of Imp activity did not cause a similar defect. Here we also characterize the Imp protein and show that it interacts with Sqd and Hrp48, two proteins that regulate expression of and mRNAs. Mutation of the gene does not substantially alter or expression. Nevertheless, the mutant partially suppresses a misexpression phenotype, arguing that it does contribute to regulation but may act redundantly Itraconazole (Sporanox) and does not have an essential role. Consistent with this interpretation, overexpression of Imp interferes with localization of mRNA. MATERIALS AND METHODS Fly stocks and transgenics. A full-length cDNA (expressed sequence tag [EST] clone SD07045) was cloned into a UASp vector (33), Itraconazole (Sporanox) and transgenic stocks were generated by standard methods. Multiple independent driver. Fly stocks (now called and chromosome were removed by extensive backcrossing to flies. The kinesin-LacZ reporter (3) was obtained from David Stein, the and flies were from Trudi Schupbach, and the TauGFP flies were from Daniel St Johnston. Plasmid rescue was performed to confirm that the P element of is inserted into the gene. The lethality of was confirmed to be due.