Knockout of Staufen1 impairs the localization of specific subsets of mRNAs on the mitotic spindle of colorectal cancer cells

Staufen1 (STAU1) is an RNA-binding protein involved in maturation, localization, translation and decay of mRNAs. STAU1 expression is modulated during the cell cycle and decreases during mitosis. In prometaphase, STAU155 binds specific classes of mRNAs that code for proteins implicated in transcription and cell cycle regulation. In this paper, we report that STAU155 co-localizes with microtubules on the mitotic spindle in human colorectal cancer cell line HCT116, and map the molecular determinant required for this association within the N-terminal 88 amino acids (aa 25-37). Interestingly, STAU1 co-purifies with ribosomal proteins and co-localizes with active sites of translation on the mitotic spindle. To characterize STAU1-dependent mRNA transport and localization on the spindle, we used RNAseq analysis to identify spindle-associated mRNAs on purified spindles of wild-type and STAU1-KO CRISPR cell lines. Our datasets identify 161 protein-coding transcripts that are less abundant on the mitotic spindle of STAU1-KO cells compared to WT, and 660 that are more abundant. Altogether, these data demonstrate that STAU1 controls the transport and the localization of specific sub-populations of mRNAs to the mitotic spindle of cancer cells and suggest that at least some spindle-localized mRNAs undergo local translation during mitosis. WT and STAU1-KO HCT116 cells were synchronized in mitosis with Taxol and RNAs purified from whole cell extracts and from mitotic spindle preparations. Biological replicates were analyzed.