Abstract
BackgroundStaufen2 (Stau2), a double-stranded RNA-binding protein, is a component of neuronal RNA granules, which are dendritic mRNA transport machines. Although Stau2 is thought to be involved in the dendritic targeting of several mRNAs in neurons, the mechanism whereby Stau2 regulates these mRNAs is unknown. To elucidate the functions of Stau2, we screened for novel binding partners by affinity purification of GST-tagged Stau2 from 293F cells.ResultsThree RNA helicases, RNA helicase A, Upf1 and Mov10, were identified in Stau2-containing complexes. We focused our studies on Upf1, a key player in nonsense-mediated mRNA decay. Stau2 was found to bind directly to Upf1 in an RNA-independent manner in vitro. Tethering Stau2 to the 3'-untranslated region (UTR) of a reporter gene had little effect on its expression in HeLa cells. In contrast, when the same tethering assay was performed in 293F cells, we observed an increase in reporter protein levels. This upregulation of protein expression by Stau2 turned out to be dependent on Upf1. Moreover, we found that in 293F cells, Stau2 upregulates the reporter mRNA level in an Upf1-independent manner.ConclusionsThese results indicate that the recruitment of Stau2 alone or in combination with Upf1 differentially affects the fate of mRNAs. Moreover, the results suggest that Stau2-mediated fate determination could be executed in a cell type-specific manner.
Highlights
Staufen2 (Stau2), a double-stranded RNA-binding protein, is a component of neuronal RNA granules, which are dendritic mRNA transport machines
These results indicate that the recruitment of Stau2 alone or in combination with Upf1 differentially affects the fate of mRNAs
Given that the HEK 293 cell line has been suspected to be of a neuronal cell lineage rather than a kidney epithelial cell lineage [18] and that Stau2 has been reported to be involved in mRNA regulation in neurons [4,6,7], interaction counterparts in the 293F cell line were attractive targets
Summary
Staufen (Stau2), a double-stranded RNA-binding protein, is a component of neuronal RNA granules, which are dendritic mRNA transport machines. After being exported to the cytoplasm, the expression of mRNAs is further modulated by the regulation of their localization, stability and rate of translation. Some mRNAs are localized at specific sites in the cytoplasm and are translated locally, enabling the spatiotemporal regulation of protein expression. The depletion of Stau in mature hippocampal neurons by RNA interference (RNAi) reduces the number of dendritic spines, suggesting that Stau regulates the targeting, translation and/or stabilization of the mRNAs involved in spine morphogenesis [7]. Interactions of Stau with the mRNA binding proteins Tap and the Y14-Magoh heterodimer [5] have been reported, little is currently known concerning the functions of Stau in mRNA regulation. Functional differences among the isoforms are not well known
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