Abstract
BackgroundIn phylogenetically diverse organisms, the 5′ ends of a subset of mRNAs are trans-spliced with a spliced leader (SL) RNA. The functions of SL trans-splicing, however, remain largely enigmatic.ResultsWe quantified translation genome-wide in the marine chordate, Oikopleura dioica, under inhibition of mTOR, a central growth regulator. Translation of trans-spliced TOP mRNAs was suppressed, consistent with a role of the SL sequence in nutrient-dependent translational control of growth-related mRNAs. Under crowded, nutrient-limiting conditions, O. dioica continued to filter-feed, but arrested growth until favorable conditions returned. Upon release from unfavorable conditions, initial recovery was independent of nutrient-responsive, trans-spliced genes, suggesting animal density sensing as a first trigger for resumption of development.ConclusionOur results are consistent with a proposed role of trans-splicing in the coordinated translational down-regulation of nutrient-responsive genes under growth-limiting conditions.
Highlights
In phylogenetically diverse organisms, the 5′ ends of a subset of mRNAs are trans-spliced with a spliced leader (SL) RNA
We confirmed that exposing female O. dioica to the mammalian target of rapamycin (mTOR) inhibitor Torin 1, in seawater, resulted in the expected absence of phosphorylated 4E-BP1 (Fig. 1a and Additional file 1: Figure S1): phosphorylated 4E binding protein 1 (4EBP1) was absent after 1.5 h of treatment, similar to what was observed in mouse embryonic fibroblast (MEF) cells [9]
We demonstrated that the commercial antibody we used was specific to the phosphorylated form of 4E-BP1 in O. dioica, as it is in other species (Additional file 1: Figure S1E)
Summary
The 5′ ends of a subset of mRNAs are trans-spliced with a spliced leader (SL) RNA. The functions of SL trans-splicing, remain largely enigmatic. In a phylogenetically disparate group of organisms [1, 2] mRNAs undergo trans-splicing [3] where a separately transcribed RNA molecule, called a spliced leader (SL), is added to their 5′ ends. An important function of this process is to resolve polycistronic RNA transcribed from operons, allowing their translation as monocistrons. Monocistronic transcripts, are trans-spliced [4]. The function in these cases has so far remained largely enigmatic
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