The mammalian/mechanistic target of rapamycin (mTOR) is a key component of cellular metabolism that integrates nutrient sensing with cellular processes that fuel cell growth and proliferation. Although the involvement of the mTOR pathway in regulating life span and aging has been studied extensively in the last decade, the underpinning mechanisms remain elusive. In this review, we highlight the emerging insights that link mTOR to various processes related to aging, such as nutrient sensing, maintenance of proteostasis, autophagy, mitochondrial dysfunction, cellular senescence, and decline in stem cell function.

Staufen1 is a component of transported ribonucleoprotein complexes. Genetic work in Drosophila has suggested that Staufen plays a role in the de-repression of translation of oskar mRNA following localization. To determine whether Staufen1 can play a similar role in mammals, we studied translation of transcripts in the presence or in the absence of Staufen1. Translationally repressed mRNAs were generated by fusing the structured human immunodeficiency virus type 1 trans-activating response (TAR) element to the 5′ end of a reporter transcript. In rabbit reticulocyte lysates and in mammalian cultured cells, the addition of Staufen1 resulted in the up-regulation of reporter activity when translation was driven by the TAR-bearing RNA. In contrast, Staufen1 had no effect on translation of efficiently translated mRNAs lacking an apparent structured 5′ end, suggesting that Staufen1-binding to the 5′ end is required for enhanced translation. Consistently, Staufen1 RNA-binding activity is necessary for this translational effect. In addition, similar up-regulation of translation was observed when Staufen1 was tethered to the 5′ end of mRNAs via other structured RNAs, the highest level of translational increase being obtained with the bona fide Staufen1-binding site of the Arf1 transcript. The expression of Staufen1 promoted polysomal loading of TAR-luciferase transcripts resulting in enhanced translation. Our results support a model in which the expression of Staufen1 and its interaction with the 5′ end of RNA and ribosomes facilitate translation initiation.

Synonymous mutations have been viewed as silent mutations, since they only affect the DNA and mRNA, but not the amino acid sequence of the resulting protein. Nonetheless, recent studies suggest their significant impact on splicing, RNA stability, RNA folding, translation or co-translational protein folding. Hence, we compile 659194 synonymous mutations found in human cancer and characterize their properties. We provide the user-friendly, comprehensive resource for synonymous mutations in cancer, SynMICdb ( http://SynMICdb.dkfz.de ), which also contains orthogonal information about gene annotation, recurrence, mutation loads, cancer association, conservation, alternative events, impact on mRNA structure and a SynMICdb score. Notably, synonymous and missense mutations are depleted at the 5'-end of the coding sequence as well as at the ends of internal exons independent of mutational signatures. For patient-derived synonymous mutations in the oncogene KRAS , we indicate that single point mutations can have a relevant impact on expression as well as on mRNA secondary structure.

In developed countries, the leading causes of blindness such as diabetic retinopathy are characterized by disorganized vasculature that can become fibrotic. Although many such pathological vessels often naturally regress and spare sight-threatening complications, the underlying mechanisms remain unknown. Here, we used orthogonal approaches in human patients with proliferative diabetic retinopathy and a mouse model of ischemic retinopathies to identify an unconventional role for neutrophils in vascular remodeling during late-stage sterile inflammation. Senescent vasculature released a secretome that attracted neutrophils and triggered the production of neutrophil extracellular traps (NETs). NETs ultimately cleared diseased endothelial cells and remodeled unhealthy vessels. Genetic or pharmacological inhibition of NETosis prevented the regression of senescent vessels and prolonged disease. Thus, clearance of senescent retinal blood vessels leads to reparative vascular remodeling.

Staufen1 (Stau1) is a ribonucleic acid (RNA)-binding protein involved in the post-transcriptional regulation of gene expression. Recent studies indicate that Stau1-bound messenger RNAs (mRNAs) mainly code for proteins involved in transcription and cell cycle control. Consistently, we report here that Stau1 abundance fluctuates through the cell cycle in HCT116 and U2OS cells: it is high from the S phase to the onset of mitosis and rapidly decreases as cells transit through mitosis. Stau1 down-regulation is mediated by the ubiquitin-proteasome system and the E3 ubiquitin ligase anaphase promoting complex/cyclosome (APC/C). Stau1 interacts with the APC/C co-activators Cdh1 and Cdc20 via its first 88 N-terminal amino acids. The importance of controlling Stau155 levels is underscored by the observation that its overexpression affects mitosis entry and impairs proliferation of transformed cells. Microarray analyses identified 275 Stau155-bound mRNAs in prometaphase cells, an early mitotic step that just precedes Stau1 degradation. Interestingly, several of these mRNAs are more abundant in Stau155-containing complexes in cells arrested in prometaphase than in asynchronous cells. Our results point out for the first time to the possibility that Stau1 participates in a mechanism of post-transcriptional regulation of gene expression that is linked to cell cycle progression in cancer cells.

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Background: The formation of new infectious human immunodeficiency type 1 virus (HIV-1) mainly relies on the homo-multimerization of the viral structural polyprotein Pr55 Gag and on the recruitment of host factors. We have previously shown that the double-stranded RNA-binding protein Staufen 1 (Stau1), likely through an interaction between its third double-stranded RNAbinding domain (dsRBD3) and the nucleocapsid (NC) domain of Pr55 Gag , participates in HIV-1 assembly by influencing Pr55 Gag multimerization.

Transport of mRNA is an efficient mechanism to target proteins to specific regions of a cell. Although it is well documented that mRNAs are transported in ribonucleoprotein (RNP) complexes, several of the mechanisms involved in complex formation and localization are poorly understood. Staufen (Stau) 1, a double-stranded RNA-binding protein, is a well accepted marker of mRNA transport complexes. In this manuscript, we provide evidence that Stau1 self-associates in live cells using immunoprecipitation and bioluminescence resonance energy transfer (BRET) assays. The double-stranded RNA-binding domains dsRBD3 and dsRBD4 contributed about half of the signal, suggesting that Stau1 RNA-binding activity is involved in Stau1 selfassociation. Protein-protein interaction also occurred, via dsRBD5 and dsRBD2, as shown by in vitro pull-down, yeast twohybrid, and BRET assays in live cells. Interestingly, Stau1 self-association contributes to the formation of oligomeric complexes as evidenced by the coexpression of split Renilla luciferase halves covalently linked to Stau1 in a protein complementation assay (PCA) combined with a BRET assay with Stau1-YFP. Moreover, we showed that these higher-order Stau1-containing complexes carry RNAs when the RNA stain SYTO 14 was used as the energy acceptor in the PCA/BRET assay. The oligomeric composition of Stau1-containing complexes and the presence of specific mRNAs have been confirmed by biochemical approaches involving two successive immunoprecipitations of Stau1-tagged molecules followed by qRT-PCR amplification. Altogether, these results indicate that Stau1 self-associates in mRNPs via its multiple functional domains that can select mRNAs to be transported and establish protein-protein interaction.