mRNA localization is linked to translation regulation in theCaenorhabditis elegansgerm lineage

Abstract

Caenorhabditis elegans early embryos generate cell-specific transcriptomes despite lacking active transcription. This presents an opportunity to study mechanisms of post-transcriptional regulatory control. In seeking the mechanisms behind this patterning, we discovered that some cell-specific mRNAs accumulate non-homogenously within cells, localizing to membranes, P granules (associated with progenitor germ cells in the P lineage), and P-bodies (associated with RNA processing). Transcripts differed in their dependence on 3'UTRs and RNA Binding Proteins, suggesting diverse regulatory mechanisms. Notably, we found strong but imperfect correlations between low translational status and P granule localization within the progenitor germ lineage. By uncoupling these, we untangled a long-standing question: Are mRNAs directed to P granules for translational repression or do they accumulate there as a downstream step? We found translational repression preceded P granule localization and could occur independent of it. Further, disruption of translation was sufficient to send homogenously distributed mRNAs to P granules. Overall, we show transcripts important for germline development are directed to P granules by translational repression, and this, in turn, directs their accumulation in the progenitor germ lineage where their repression can ultimately be relieved. SummaryMaternally loaded mRNAs localize non-homogeneously within C. elegans early embryos correlating with their translational status and lineage-specific fates.

EDC-3 and EDC-4 Regulate Embryonic mRNA Clearance and Biomolecular Condensate Specialization

“…However, this activity is predominantly observed in embryos from the 4-cell to the 20-cell, after which CSR-1 expression in the soma diminishes 85 . Additionally, members of the AU-rich element binding, CCCH finger family of proteins, MEX-3, MEX-5 and MEX- 6, promote the decay of specific maternal transcripts (nos-2, cpg-2, chs-1) in the soma, also up to ~20-cell, after which the MEX proteins are depleted from the soma and remain enriched in the germline lineage 4,86,87 .…”

The multiscale and multiphase organization of the transcriptome

“…(B) The condensation of RBPs can alternatively inhibit their interaction with mRNA targets, as observed upon Pab1, Ded1p, or Whi3 condensation upon stress [87,95,135]. (C) Some RNAs can be released from droplets into the cytosol, while others are retained in a condensed state, as exemplified by maternal mRNAs during early embryonic development whose release from germ granules correlatess with the different temporal waves of translation activation [8,148]. Granule material properties can fine-tune RNA exchange.…”