Multifunctional RNA-binding proteins influence mRNA abundance and translational efficiency of distinct sets of target genes

RNA-binding proteins (RBPs) can regulate more than a single aspect of RNA metabolism. We searched for such previously undiscovered multifunctionality within a set of 143 RBPs, by defining the predictive value of RBP abundance for the transcription and translation levels of known RBP target genes across 80 human hearts. This led us to newly associate 27 RBPs with cardiac translational regulation in vivo. Of these, 21 impacted both RNA expression and translation, albeit for virtually independent sets of target genes. We highlight a subset of these, including G3BP1, PUM1, UCHL5, and DDX3X, where dual regulation is achieved through differential affinity for target length, by which separate biological processes are controlled. Like the RNA helicase DDX3X, the known splicing factors EFTUD2 and PRPF8 - all identified as multifunctional RBPs by our analysis - selectively influence target translation rates depending on 5' UTR structure. Our analyses identify dozens of RBPs as being multifunctional and pinpoint potential novel regulators of translation, postulating unanticipated complexity of protein-RNA interactions at consecutive stages of gene expression

Dual-function RNA-binding proteins influence mRNA abundance and translational efficiency of distinct sets of target genes

RNA-binding proteins (RBPs) are key regulators of RNA metabolism. Many RBPs possess uncharacterized RNA-binding domains and localize to multiple subcellular compartments, suggesting their involvement in multiple biological processes. We searched for such multifunctionality within a set of 143 RBPs by integrating experimentally validated target genes with the transcriptomes and translatomes of 80 human hearts. This revealed that RBP abundance is predictive of the extent of target regulation in vivo, leading us to newly associate 27 RBPs with translational control. Amongst those were several splicing factors, of which the muscle specific RBM20 modulated target translation rates through switches in isoform production. For 21 RBPs, we newly observed dual regulatory effects impacting both mRNA levels and translation rates, albeit for virtually independent sets of target genes. We highlight a subset, including G3BP1, PUM1, UCHL5, and DDX3X, where dual regulation is achieved by differential affinity for targets of distinct length and functionality. Strikingly, in a manner very similar to DDX3X, the known splicing factors EFTUD2 and PRPF8 selectively influence target translation rates depending on 5’ UTR structure. Our results indicate unanticipated complexity of protein-RNA interactions at consecutive stages of gene expression and implicate multiple core splicing factors as key regulators of translational output

A human ESC-based screen identifies a role for the translated lncRNA LINC00261 in pancreatic endocrine differentiation

Long noncoding RNAs (lncRNAs) are a heterogenous group of RNAs, which can encode small proteins. The extent to which developmentally regulated lncRNAs are translated and whether the produced microproteins are relevant for human development is unknown. Using a human embryonic stem cell (hESC)-based pancreatic differentiation system, we show that many lncRNAs in direct vicinity of lineage-determining transcription factors (TFs) are dynamically regulated, predominantly cytosolic, and highly translated. We genetically ablated ten such lncRNAs, most of them translated, and found that nine are dispensable for pancreatic endocrine cell development. However, deletion of LINC00261 diminishes insulin(+) cells, in a manner independent of the nearby TF FOXA2. One-by-one deletion of each of LINC00261's open reading frames suggests that the RNA, rather than the produced microproteins, is required for endocrine development. Our work highlights extensive translation of lncRNAs during hESC pancreatic differentiation and provides a blueprint for dissection of their coding and noncoding roles

The translational landscape of the human heart

Gene expression in human tissue has primarily been studied on the transcriptional level, largely neglecting translational regulation. Here, we analyze the translatomes of 80 human hearts to identify new translation events and quantify the effect of translational regulation. We show extensive translational control of cardiac gene expression, which is orchestrated in a process-specific manner. Translation downstream of predicted disease-causing protein-truncating variants appears to be frequent, suggesting inefficient translation termination. We identify hundreds of previously undetected microproteins, expressed from lncRNAs and circRNAs, for which we validate the protein products in vivo. The translation of microproteins is not restricted to the heart and prominent in the translatomes of human kidney and liver. We associate these microproteins with diverse cellular processes and compartments and find that many locate to the mitochondria. Importantly, dozens of microproteins are translated from lncRNAs with well-characterized noncoding functions, indicating previously unrecognized biology