Distinct domains mediate the early and late functions of the Drosophila ovarian tumor proteins

Abstract

The Drosophila melanogaster ovarian tumor (otu) gene encodes two novel protein isoforms that are required at multiple stages of oogenesis. We have examined the activity of a set of C-terminal truncation Otu proteins as well as a GFP-tagged Otu (Otu-GFP). These experiments have shown that a putative Tudor domain in the central region of the large Otu isoform and a separate domain in the C-terminal region are required for regulation of cyst formation and oocyte maturation, respectively. We also present evidence that a portion of Otu co-fractionates with mRNA/protein complexes (mRNPs) and show that Otu-GFP associates with cytoplasmic aggregates at periphery of the nucleus at an intermediate stage of oogenesis. This study substantially clarifies the relationship between Otu structure and function and reveals new clues about interacting components.

Drosophila tudor is essential for polar granule assembly and pole cell specification, but not for posterior patterning

“…Furthermore, no conclusive experimental evidence has been reported specifically linking Tudor domains to RNA metabolism. Rather, mutations or deletions of Tudor domains in the human Survival Motor Neuron protein (SMN) affect proteinprotein interactions, while deletion of the Tudor domain of Drosophila Ovarian Tumor (OTU) protein does not disrupt the association of OTU with mRNPs (Buhler et al, 1999;Glenn and Searles, 2001;Selenko et al, 2001). While TUD is clearly in close association with RNAs in the Drosophila pole plasm, whether it directly binds RNA remains an open question that is not readily addressed through sequence comparisons.…”

Hrb27C, Sqd and Otu cooperatively regulategurkenRNA localization and mediate nurse cell chromosome dispersion inDrosophilaoogenesis

“…Immunoprecipitations were performed according to Van Buskirk et al (Van Buskirk et al, 2000) with the following modifications: a complete mini protease inhibitor cocktail tablet (Roche) was used in lieu of other protease inhibitors in the lysis buffer, 1U/µl RNAse inhibitor (Roche) was added to the lysis buffer, lysates were not pre-cleared with pre-immune serum coated beads, and lysates were rotated with the antibody coated beads for 60 minutes at 4°C. The following antibodies were used: monoclonal anti-Sqd serum (8F3; 3:10 dilution), monoclonal anti-SpnF serum (10D8; 3:10 dilution) (U. Abdu, unpublished), polyclonal anti-Otu (guinea pig against amino acids 1-338; 1:10 dilution) (Glenn and Searles, 2001) or polyclonal anti-Odd skipped (1:10 dilution) (Kosman et al, 1998). For RNAse treated samples, 1 µg/µl RNAse A was added to the lysis buffer instead of RNAse inhibitor.…”

“…As otu mutants also show defects in osk localization (Tirronen et al, 1995), it appears that like several other factors, Otu is required for both grk and osk localization. Additionally, Otu has been isolated from cytoplasmic mRNP complexes (Glenn and Searles, 2001). …”

Tudor and its domains: germ cell formation from a Tudor perspective

“…Moreover, recent experimental evidence does not support an RNA-binding function for the Tudor domain. For example, the Drosophila OVARIAN TUMOR (OTU) protein contains a single Tudor domain and is associated with mRNPs, but deletion of its Tudor domain did not disrupt its ability to associate with mRNPs [35].…”