Translational activity of 80S monosomes varies dramatically across different tissues

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• Translational control influences protein synthesis by regulating ribosome numbers per mRNA.
• Single 80S ribosomes (monosomes) are the predominant ribosomal complexes in vivo, yet their translational activity is poorly understood.
• Understanding monosome activity is crucial for deciphering gene expression regulation.

Purpose of the Study:

• To investigate the translational activity of 80S monosomes in different tissues of Drosophila melanogaster.
• To characterize the mRNA features translated by active monosomes.
• To elucidate the differential roles of monosomes and polysomes in protein production across tissues.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to assess 80S monosome translational activity.
• RNA sequencing (RNA-Seq) was performed on mRNAs translated by monosomes and polysomes from Drosophila heads.
• Bioinformatic analysis was used to identify characteristics of actively translated mRNAs.

Main Results:

• 80S monosomes exhibited high translational activity in Drosophila heads and embryos.
• Conversely, 80S monosomes were translationally inactive in testes and ovaries.
• Head monosome-translated mRNAs were enriched for TOP motifs, short 5'-UTRs, short ORFs, and upstream ORFs (uORFs).

Conclusions:

• Monosomes are key regulators of translation initiation and protein synthesis in Drosophila heads and embryos.
• Polysomes are the primary drivers of protein production in Drosophila testes and ovaries.
• Tissue-specific translational regulation by monosomes contributes to differential protein synthesis.