An interaction network of RNA-binding proteins involved in Drosophila oogenesis

Prashali Bansal; Johannes Madlung; Kristina Schaaf; Boris Macek; Fulvia Bono

The post-transcriptional regulation of gene expression requires several trans-acting factors that regulate the life cycle of an mRNA (1) . Many of these factors are RNA-binding proteins (RBPs) that interact with the maturing mRNAs to form functional messenger ribonucleoprotein complexes (mRNPs), interconnecting various steps of RNA metabolism, thereby controlling gene expression (1) (2) (3) . In Drosophila oogenesis, mRNPs are first assembled in the nurse cell nucleus, providing a platform for the formation of larger dynamic assemblies in the cytoplasm, regulating mRNA transport, silencing and localized translation. Several RBPs have been identified and extensively studied in Drosophila development. Some of the well characterized and evolutionary conserved examples include the dsRNA-binding protein Staufen (Stau) (4) (5) (6) (7) (8) (9) (10) (11) , the DEAD-box helicases Vasa (Vas) (12) (13) (14) (15) (16) (17) (18) (19) (20) and eIF4AIII (21) (22) (23) (24) (25) , the CCHC-type zinc finger protein Nanos (Nos) (26) (27) (28) (29) (30) and the heterogeneous nuclear ribonucleoproteins (hnRNPs) Hrp48 and Glorund (Glo) (31-33). Binding of these proteins is essential for the proper expression of four key maternal transcripts: bicoid (bcd), oskar (osk), gurken (grk) and nanos (nos), critical to define the future embryonic axes. In addition to their functions in establishing oocyte polarity, these RBPs have various other roles during Drosophila oogenesis. For example, Hrp48 and Glo are required in nurse cells for the regulation of chromosome organization (38, 47). They have also been implicated as regulators of alternative splicing,