FUS (RNA-binding protein FUS) is a DNA/RNA-binding protein that plays a role in various cellular processes such as transcription regulation, RNA splicing, RNA transport, DNA repair and damage response. It binds to nascent pre-mRNAs and acts as a molecular mediator between RNA polymerase II and U1 small nuclear ribonucleoprotein thereby coupling transcription and splicing. It binds also its own pre-mRNA and autoregulates its expression; this autoregulation mechanism is mediated by non-sense-mediated decay. FUS plays a role in DNA repair mechanisms by promoting D-loop formation and homologous recombination during DNA double-strand break repair. In neuronal cells, FUS plays crucial roles in dendritic spine formation and stability, RNA transport, mRNA stability and synaptic homeostasis.