Precise Temporal Regulation of Post-transcriptional Repressors Is Required for an Orderly Drosophila Maternal-to-Zygotic Transition

Abstract

SUMMARY In animal embryos, the maternal-to-zygotic transition (MZT) hands developmental control from maternal to zygotic gene products. We show that the maternal proteome represents more than half of the protein-coding capacity of Drosophila melanogaster’s genome, and that 2% of this proteome is rapidly degraded during the MZT. Cleared proteins include the post-transcriptional repressors Cup, Trailer hitch (TRAL), Maternal expression at 31B (ME31B), and Smaug (SMG). Although the ubiquitin-proteasome system is necessary for clearance of these repressors, distinct E3 ligase complexes target them: the C-terminal to Lis1 Homology (CTLH) complex targets Cup, TRAL, and ME31B for degradation early in the MZT and the Skp/Cullin/F-box-containing (SCF) complex targets SMG at the end of the MZT. Deleting the C-terminal 233 amino acids of SMG abrogates F-box protein interaction and confers immunity to degradation. Persistent SMG downregulates zygotic re-expression of mRNAs whose maternal contribution is degraded by SMG. Thus, clearance of SMG permits an orderly MZT.

Proteomic analysis of ubiquitination substrates reveals a CTLH E3 ligase complex‐dependent regulation of glycolysis

“…16,19,20 The drosophila CTLH complex with the UBE2H homologue (named Kdo) is responsible for timed proteasomal degradation of an essential RNA binding complex during the maternal to zygotic transition. 53,54 This is also consistent with the yeast Gid complex ubiquitination of gluconeogenic enzymes, which results in their proteasomal degradation. 5 Thus, our findings provide the first evidence that CTLH complex ubiquitination affects a protein other than through…”

DIA-based systems biology approach unveils E3 ubiquitin ligase-dependent responses to a metabolic shift

“…While the role of the GID ligase in the regulation of gluconeogenesis is well-characterized, the conservation of this multiprotein complex throughout eukaryotes suggests that it likely regulates additional pathways. For example, the GID/CTLH complex has a role in erythropoiesis and spermatogenesis in human cells and in embryogenesis in Drosophila ( 62 – 65 ). Thus, we set out to uncover additional pathways regulated by the GID E3 ligase in yeast by utilizing a combination of mutants.…”

GID E3 ligase supramolecular chelate assembly configures multipronged ubiquitin targeting of an oligomeric metabolic enzyme

“…Mammals even have two orthologs, WDR26 and MKLN1, which are subunits of the “CTLH” complex that corresponds to the yeast GID E3 ( Boldt et al., 2016 ; Francis et al., 2013 ; Kobayashi et al., 2007 ; Lampert et al., 2018 ; Liu and Pfirrmann, 2019 ; Salemi et al., 2017 ). The CTLH E3, named for the preponderance of CTLH domains (in Gid1, Gid2, Gid7, Gid8, and Gid9 and their orthologs), has intrinsic E3 ligase activity, although Pro/N-degron substrates have not yet been identified despite human Gid4 binding this motif ( Cao et al., 2020 ; Dong et al., 2018 ; Lampert et al., 2018 ; Liu et al., 2020 ; Liu and Pfirrmann, 2019 ; Maitland et al., 2019 ; Zavortink et al., 2020 ).…”