A novel and unanticipated link between the Werner syndrome protein (WRN) and protein translation

Background

Loss-of-function of WRN is the cause of Werner Syndrome (WS), a rare autosomal recessive and progressive genetic disorder, which is the responsible of the premature aging in young adults and accompanied by age-related diseases such as rare forms of cancer and type 2 diabetes. WRN is a nuclear protein that play a role in many DNA processes, however its action in cells is poorly understood. Previously we demonstrate that downregulation of WRN induces a metabolic shift that compromises redox homeostasis and limits cancer cell proliferation due to a dysregulation of metabolic proteins, independently of gene expression. Here, we present our preliminary data showing that a small fraction of WRN localize with translational machinery and its absence alter the proper function of this metabolic pathway.

Methods

Depletion of WRN in Hela cells was carry out by a conditional lentivirus silencing system (shWRN) and activated by doxycycline for 3 days. The level of WRN protein after treatment was confirm by western blot. For control, we used a non-redundant shRNA. A combination of differential centrifugation, sucrose gradient centrifugation, metabolic labeling, immunofluorescence, RT-qPCR, western blot and bioinformatics tools were been used for achieve our goals.

Results

Small portion of WRN localizes in the cytoplasm as a complex enriched in ribosomal proteins. Depletion of WRN induces a significant reduction of de novo protein synthesis. Cytoplasmic WRN sediments with a similar pattern to ribosomal protein RPL7a in polysome profile and both are disrupt by EDTA. The ribosome half-transit time assay revel a transit rate affected in absence of WRN with no stress granules (SGs) formation observed in WRN-depleted. Finally, in silico study of public datasets reveal that high WRN level is significantly associated with a worse prognosis in several types of neoplasia.

Conclusions

Our results suggest that: 1) reduced rates of protein synthesis is unlikely the result of a stress response; 2) Alteration in protein synthesis are likely contributing to accelerated replicative senescence of WRN depleted cells. The mechanism and nature of the translational defects caused by WRN depletion is currently under investigation.

Clinical trial identification

Legal entity responsible for the study

University of Southern California, Los Angeles, USA. Universidad Científica del Sur, Lima, Perú. ONCOSALUD, Lima, Perú.

Funding

This project was funded by grant R01AG034156 from the National Institute of Aging at the National Institutes of Health (NIH), USA, and by the grant 357-PNICP-BRI-2015 from the Programa Nacional de Innovación para la Competitividad y Productividad (INNOVATE PERU) form the Ministerio de la Producción, Perú.

Disclosure

All authors have declared no conflicts of interest.