This work has been funded in part by the European Union's Horizon 2020 Research and Innovation Program under Grant Agreement no 668031 (GALAXY: Gut-and-Liver Axis in Alcoholic Liver Fibrosis) and by Greece and the European Union (European Social Fund-ESF) through Operational Programme "Human Resources Development, Education and Lifelong Learning" in the context of the project "Strengthening Human Resources Research Potential via Doctorate Research" (MIS-5000432), implemented by the State Scholarships Foundation (IKY). The authors would like to thank Dr. Fay Christodoulou for introducing them to the AGO amazing world. We would like to express our appreciation to Mr Nicholas Kalavros for his contribution to this work in bioinformatic and technical procedures. We would also like to thank Dr. Eleni Rigana for her precious technical assistance with the confocal laser scanning microscopy and Dr. Skarlatos Dedos for kindly providing technical and scientific support, as well as reagents for the iPLA assay. Finally, we would like to thank the reviewers for the constructive criticism that allowed us to greatly improve the quality of the paper. The authors declare no competing financial interests. Conceptualization and design of the work: VIP, EA, Funding acquisition: GALAXY (HORIZON 2020) and IKY (State Scholarships Foundation), Investigation (experimental work): VIP, Resources: JT, Image analysis/ Software: AD, VF, Karyotyping/ Chromosome assays: ΕD, S. Gagos, Scientific supervision: EA, Manuscript drafting (writing): VIP, AD, S. Georgiou, JT, AV, MT, DT, ST-B, DJS, EA, Microscopy and Image Analysis consulting: SNP, TEM microscopy: IK, SEM microscopy: EC

Argonaute 2 (AGO2) is an indispensable component of the RNA-induced silencing complex, operating at the transcriptional or posttranscriptional level. It is compartmentalized into structures such as GW- and P-bodies, stress granules and adherens junctions as well as the midbody. Here we show using immunofluorescence, image- and bioinformatic analysis and cytogenetics that AGO2 also resides in membrane protrusions such as open- and close-ended tubes. The latter are cytokinetic bridges where AGO2 colocalizes at the midbody-arms with cytoskeletal components such as α-Τubulin and Aurora B and various kinases. AGO2, phosphorylated on serine 387 is located together with Dicer at the midbody ring in a manner dependent on p38 MAPK activity. We further show that AGO2 is stress sensitive and important to ensure the proper chromosome segregation and cytokinetic fidelity. We suggest that AGO2 is part of a regulatory mechanism triggered by cytokinetic stress to generate the appropriate micro-environment for local transcript homeostasis. Statement: AGO2 resides in open-ended tunneling nanotubes and close-ended cytokinetic bridges. At the latter location AGO2 colocalises with cell division components and the authors show that AGO2 deregulation impairs cell division fidelity.