Biology subjects

Palazzo, A. F.

Publications and source records attributed to Palazzo, A. F..

3 recordsLinked to original sources

bioRxiv2019

TPR is required for the nuclear export of mRNAs and lncRNAs from intronless and intron-poor genes

While splicing has been shown to enhance nuclear export, it has remained unclear whether mRNAs generated from intronless genes use specific machinery to promote their export. Here we investigate the role of the major nuclear pore basket protein, TPR, in regulating mRNA and lncRNA nuclear export in human cells. By sequencing mRNA from the nucleus and cytosol of control and TPR-depleted cells, we provide evidence that TPR is required for the nuclear export of mRNAs and lncRNAs that are generated from intronless and intron-poor genes, and we validate this with reporter constructs. Moreover, in TPR-depleted cells reporter mRNAs generated from intronless genes accumulate in nuclear speckles and are bound to Nxf1. These observations suggest that TPR acts downstream of Nxf1 recruitment, and may allow mRNAs to leave nuclear speckles and properly dock with the nuclear pore. In summary, our study provides one of the first examples of a factor that is required for the nuclear export of intronless and intron-poor mRNAs and lncRNAs.

molecular biology↗

bioRxiv2019

Pyruvate Kinase M Links Glucose Availability to Protein Synthesis

How human cells coordinate various metabolic processes, such as glycolysis and protein translation, remains unclear. One key insight is that various metabolic enzymes have been found to associate with mRNAs, however whether these enzymes regulate mRNA biology in response to changes in cellular metabolic state remains unknown. Here we report that the glycolytic enzyme, pyruvate kinase M (PKM), inhibits the translation of 7% of the transcriptome in response to elevated levels of glucose and pyruvate. Our data suggest that in the presence of glucose and pyruvate, PKM associates with ribosomes that are synthesizing stretches of polyacidic nascent polypeptides and stalls the elongation step of translation. PKM-regulated mRNAs encode proteins required for the cell cycle and may explain previous results linking PKM to cell cycle regulation. Our study uncovers an unappreciated link between glycolysis and the ribosome that likely coordinates the intake of glycolytic metabolites with the regulation of protein synthesis and the cell cycle.

molecular biology↗

bioRxiv2019

RanBP2/Nup358 enhances RNAi activity by sumoylating and stabilizing Argonaute 1

RanBP2/Nup358 is one of the main components of the cytoplasmic filaments of the nuclear pore complex. It has been speculated that RanBP2, which has an E3 SUMO-ligase domain, may alter the composition of messenger ribonucleoprotein (mRNP) complexes as they emerge from the nuclear pore and thus regulate the ultimate fate of the mRNA in the cytoplasm. Four separate missense mutations in RanBP2 cause Acute Necrotizing Encephalopathy 1 (ANE1), which manifests as a sharp rise in cytokine production after common viral infections such as influenza and parainfluenza. However, how RanBP2 and its ANE1-associated mutations affect cytokine production is not well understood. Here we report that RanBP2 represses the translation of the interleukin-6 (IL6) mRNA, which encodes a cytokine that is aberrantly up-regulated in ANE1. Our data indicates that soon after its production, the IL6 mRNP recruits the RNA-induced silencing complex (RISC) bound to Let7 miRNA. After this mRNP is exported, RanBP2 sumoylates the RISC-component AGO1, thereby stabilizing it and enforcing mRNA silencing. Collectively, these results support a model whereby RanBP2 promotes an mRNP remodelling event that is critical for the miRNA-mediated suppression of clinically relevant mRNAs, such as IL6.

molecular biology↗