The regulatory landscape of 5′ UTRs in translational control during zebrafish embryogenesis

Abstract

SummaryThe 5′ UTRs of mRNAs are critical for translation regulation, but theirin vivoregulatory features are poorly characterized. Here, we report the regulatory landscape of 5′ UTRs during early zebrafish embryogenesis using a massively parallel reporter assay of 18,154 sequences coupled to polysome profiling. We found that the 5′ UTR is sufficient to confer temporal dynamics to translation initiation, and identified 86 motifs enriched in 5′ UTRs with distinct ribosome recruitment capabilities. A quantitative deep learning model, DaniO5P, revealed a combined role for 5′ UTR length, translation initiation site context, upstream AUGs and sequence motifs onin vivoribosome recruitment. DaniO5P predicts the activities of 5′ UTR isoforms and indicates that modulating 5′ UTR length and motif grammar contributes to translation initiation dynamics. This study provides a first quantitative model of 5′ UTR-based translation regulation in early vertebrate development and lays the foundation for identifying the underlying molecular effectors.HighlightsIn vivoMPRA systematically interrogates the regulatory potential of endogenous 5′ UTRsThe 5′ UTR alone is sufficient to regulate the dynamics of ribosome recruitment during early embryogenesisThe MPRA identifies 5′ UTRcis-regulatory motifs for translation initiation control5′ UTR length, upstream AUGs and motif grammar contribute to the differential regulatory capability of 5′ UTR switching isoforms

Ribosomal dormancy at the nexus of ribosome homeostasis and protein synthesis

“…Indeed, zebrafish embryos show a gradual increase in a subset of mRNA translation as the embryogenesis progresses. [115] Thus, there could be gradual events of translation activation during recovery and different forms of dormant ribosomes might get activated by dedicated regulators.…”