Staufen1 localizes to the mitotic spindle and controls the transport of RNA populations to the spindle

Abstract

Staufen1 (STAU1) is an RNA-binding protein involved in the posttranscriptional regulation of mRNAs. We report that a large fraction of STAU1 localizes to the mitotic spindle in the colorectal cancer HCT116 and in the non-transformed hTERT-RPE1 cells. Spindle-associated STAU1 partly co-localizes with ribosomes and active sites of translation. We mapped the molecular determinant required for STAU1/spindle association within the first 88 N-terminal amino acids, a domain that is not required for RNA binding. Interestingly, transcriptomic analysis of purified mitotic spindles reveals that 1054 mRNAs as well as the precursor ribosomal RNA and lncRNAs and snoRNAs involved in ribonucleoprotein assembly and processing are enriched on spindles compared to cell extracts. STAU1 knockout causes the displacement of the pre-rRNA and of 154 mRNAs coding for proteins involved in actin cytoskeleton organization and cell growth, highlighting a role for STAU1 in mRNA trafficking to spindle. These data demonstrate that STAU1 controls the localization of sub-populations of RNAs during mitosis and suggests a novel role of STAU1 in pre-rRNA maintenance during mitosis, ribogenesis and/or nucleoli reassembly. SUMMARY STATEMENTProper localization and functions of macromolecules during cell division are crucial to ensure survival and proliferation of daughter cells.