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

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

In contrast to Vas, Hrp48 is a known translational repressor (45-47). In line with the localization of Hrp48 to P-bodies (111), we co-purified several components of the mRNA decay machinery, including the CCR4-NOT deadenylase complex with Hrp48-GFP. It is possible that these interactions are indirect and mediated by BicaudalC (BicC) and Belle (Bel). These proteins negatively regulate target mRNAs together with the CCR4-NOT complex (112, 113) . We demonstrated in vitro binding of Hrp48 with both BicC and Bel. This suggests that by recruiting these proteins, Hrp48 may regulate the nos and osk mRNAs, possibly via CCR4-NOT mediated deadenylation ( Fig. 8; ref. (112-115) ). The function of Hrp48 in nos regulation remains to be investigated (Fig. 8) . CC-BY-NC-ND 4.0 International license author/funder. It is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.01.08.899146 doi: bioRxiv preprint However, the parallel enrichment of ribosomal proteins and P-body-components with Hrp48-GFP indicates its bifunctional role in modulating translation. Several lines of evidence from Drosophila, including binding of Hrp48 to a derepressor element in the osk 5'UTR (45), identification of Hrp48 as a part of a protein complex functioning in translational enhancement of Hsp83 mRNA (116) and interaction of Hrp48 with CPEB (cytoplasmic polyadenylation element binding) protein Orb (this study) support the dual nature of Hrp48. hnRNP A2, the mammalian homolog of Hrp48, also exhibits the ability to mediate both translational stimulation (117) as well as repression (118) , further strengthening the argument.