A conserved role for the Zinc binding ZZ domain of the ORB2 CPEB2 RNA binding protein in translational repression of target transcripts in Drosophila S2 cells and embryos

ABSTRACT: RNA binding proteins RBPs are key components of the post transcriptional regulatory machinery. We show that the ORB2 RBP, the Drosophila ortholog of vertebrate Cytoplasmic Polyadenylation Element Binding Protein 2 CPEB2, binds to hundreds of maternally provided mRNAs in early embryos, these transcripts are translationally repressed and unstable during the maternal to zygotic transition MZT. We identify a U rich motif enriched in ORB2 targets, which confers ORB2 binding and repression to a luciferase reporter mRNA in S2 tissue culture cells. ORB2 and its human homolog CPEB2 but not ORB and CPEB1 repress translation. The C terminal Zinc binding ZZ domain of ORB2 is necessary and sufficient for repression. We mapped regions of ORB2 ZZ domain that, when substituted into the same region of ORB ZZ domain, converts the non repressive domain into a repressor. ORB2 interacts with a suite of post-transcriptional regulators in early embryos; a subset of these interactions is lost upon deletion of the ZZ domain, notably with the Cup repressive complex. Analysis of the early embryo translatome in the presence or absence of the endogenous ZZ domain, shows that ORB2 targets move onto polysomes upon ZZ domain deletion, indicating that this domain mediates translational repression of ORB2 targets during the MZT. Together, our results assign a function to the ZZ domain and support a significant role for ORB2 in post transcriptional regulation of maternal mRNAs during the Drosophila MZT.

INSTRUMENT(S): QE-HF

ORGANISM(S): Drosophila <fruit Fly, Genus> (ncbitaxon:7215)

SUBMITTER: Howard Lipshitz  

PROVIDER: MSV000098275 | MassIVE | Fri Jun 20 10:06:00 BST 2025

SECONDARY ACCESSION(S): PXD065275

REPOSITORIES: MassIVE