Abstract
Translation of mammalian telomeric G-rich RNA via the Repeat Associated non-AUG translation mechanism can produce two dipeptide repeat proteins: repeating valine-arginine (VR) and repeating glycine-leucine (GL). Their potentially toxic nature suggests that one or both must play a needed role in the cell. Using light microscopy combined with antibody staining we discovered that cultured human cells stain brightly for VR during mitosis with VR staining co-localizing with ribosomes. In vitro , VR protein represses translation in a firefly luciferase assay. Affinity purification combined with mass spectrometry identified ribosomal proteins as the major class of VR interacting proteins. Extension to mouse embryonic cerebral cortical development showed strong staining in the ventricular zone where high mitotic index neural progenitor cells proliferate and in the cortical plate where new neurons settle. These observations point to VR playing a key role in mitosis very possibly depressing global translation, a role mediated by the telomere. TEASER: The telomeric valine-arginine dipeptide repeat protein is highly expressed in mitotic cells in culture and in mouse embryonic neural tissue.