Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.04.30.071365v1?rss=1 Authors: Rayner, S. L., Cheng, F., Yang, S., Grima, N., Ke, Y. D., Au, C. G., Morsch, M., De Luca, A., Davidson, J. M., Molloy, M. P., Shi, B., Ittner, L. M., Blair, I., Chung, R. S., Lee, A. Abstract: Background: Previously, we identified missense mutations in CCNF that are causative of familial and sporadic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). CCNF encodes for the protein cyclin F, a substrate recognition component of the E3-ubiquitin ligase, SCFcyclin F. We have previously shown that mutations in CCNF cause disruptions to overall protein homeostasis; causing a build-up of ubiquitylated proteins (1) as well as defects in autophagic machinery (2). Methods: Here, we have used an unbiased proteomic screening workflow using BioID, as well as standard immunoprecipitations to identify novel interaction partners of cyclin F, identifying the interaction between cyclin F and a series of paraspeckle proteins. The homeostasis of these new cyclin F interaction partners, RBM14, NONO and SFPQ were monitored in primary neurons using immunoblotting. In addition, the homeostasis of RBM14 was compared between control and ALS/FTD patient tissue using standard IHC studies. Results: Using BioID, we found over 100 putative interaction partners of cyclin F and demonstrated that cyclin F closely associates with a number of essential paraspeckle proteins, which are stress-responsive proteins that have recently been implicated in ALS pathogenesis. We further demonstrate that the turnover of these novel binding partners are defective when cyclin F carries an ALS/FTD-causing mutation. In addition the analysis of RBM14 levels in ALS patient post-mortem tissue revealed that RBM14 levels were significantly reduced in post-mortem ALS patient motor cortex and significantly reduced in the neurons of spinal cord tissue. Conclusion: Overall, our data demonstrate that the dysregulation of paraspeckle components may be contributing factors to the molecular pathogenesis of ALS/FTD. Copy rights belong to original authors. Visit the link for more info