Identification of PNG kinase substrates uncovers interactions with the translational repressor TRAL in the oocyte-to-embryo transition

• Published in: eLife Vol. 7
• Main Authors: Hara, Masatoshi, Lourido, Sebastian, Petrova, Boryana, Lou, Hua Jane, Von Stetina, Jessica R, Kashevsky, Helena, Turk, Benjamin E, Orr-Weaver, Terry L
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 26.02.2018; eLife Sciences Publications, Ltd
• Subjects: Amino acids; Animals; BICC; Conserved sequence; Cyclin B; cytoplasmic RNPs; Developmental Biology; Drosophila; Drosophila - embryology; Drosophila - enzymology; Drosophila Proteins - metabolism; Embryos; Gene Expression Regulation, Developmental; Insects; Kinases; Libraries; maternal mRNA; ME31B; Mutation; Peptides; Phosphorylation; Preferences; Protein Interaction Mapping; Protein Processing, Post-Translational; Protein-Serine-Threonine Kinases - metabolism; Pumilio; Repressors; Research Advance; Ribonucleoproteins - metabolism; Translation; United States > US; maternal mRNA; ME31B; stem cells; Drosophila; developmental biology; BICC; Pumilio; D. melanogaster; cytoplasmic RNPs
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.33150

The Drosophila Pan Gu (PNG) kinase complex regulates hundreds of maternal mRNAs that become translationally repressed or activated as the oocyte transitions to an embryo. In a previous paper (Hara et al., 2017), we demonstrated PNG activity is under tight developmental control and restricted to this transition. Here, examination of PNG specificity showed it to be a Thr-kinase yet lacking a clear phosphorylation site consensus sequence. An unbiased biochemical screen for PNG substrates identified the conserved translational repressor Trailer Hitch (TRAL). Phosphomimetic mutation of the PNG phospho-sites in TRAL reduced its ability to inhibit translation in vitro. In vivo, mutation of dominantly suppressed mutants and restored Cyclin B protein levels. The repressor Pumilio (PUM) has the same relationship with PNG, and we also show that PUM is a PNG substrate. Furthermore, PNG can phosphorylate BICC and ME31B, repressors that bind TRAL in cytoplasmic RNPs. Therefore, PNG likely promotes translation at the oocyte-to-embryo transition by phosphorylating and inactivating translational repressors.