Cell stress modulates the subcellular localization and cellular function of an RNA helicase DDX1

DDX1 is a DEAD box-containing RNA helicase. RNA helicases have been found involved in all aspects of RNA metabolism, including transcription, pre-mRNA processing, RNA export and translation. However, the functional role of DDX1 is unclear.We found that DDX1 was a homopolymeric poly(A) RNA binding protein. We examine the subcellular distribution of DDX1 to identify possible biological functions of DDX1. DDX1 is predominantly present in the nucleus. It could be exported to the cytoplasm in response to arsenite treatment, a oxidative stress stimulus. When tristetraprolin(TTP) was overexpressed to form granular foci in the cytoplasm, immunofluorescence staining followed by confocal microscopy observation showed that DDX1 partially colocalized with TTP. In this condition, DDX1 could colocalize with HuR and TIA-1, which were markers of stress granules(SGs) formed under stress environment. Since TTP was a component of processing bodies(PBs) and SGs, our results indicated DDX1 was localized in SGs. Moreover, we observed that DDX1 could inhibit the translational activity in the stress environment. We suggest that DDX1 could relocalize into SGs as stress stimulation and there were interactions between DDX1 and TTP、 HuR, and decrease the translational activity of RNAs.