[Show abstract][Hide abstract] ABSTRACT: Staufen1 (Stau1) is a ribonucleic acid (RNA)-binding protein involved in the post-transcriptional regulation of gene expression. Recent studies indicate that Stau1-bound messenger RNAs (mRNAs) mainly code for proteins involved in transcription and cell cycle control. Consistently, we report here that Stau1 abundance fluctuates through the cell cycle in HCT116 and U2OS cells: it is high from the S phase to the onset of mitosis and rapidly decreases as cells transit through mitosis. Stau1 down-regulation is mediated by the ubiquitin-proteasome system and the E3 ubiquitin ligase anaphase promoting complex/cyclosome (APC/C). Stau1 interacts with the APC/C co-activators Cdh1 and Cdc20 via its first 88 N-terminal amino acids. The importance of controlling Stau1(55) levels is underscored by the observation that its overexpression affects mitosis entry and impairs proliferation of transformed cells. Microarray analyses identified 275 Stau1(55)-bound mRNAs in prometaphase cells, an early mitotic step that just precedes Stau1 degradation. Interestingly, several of these mRNAs are more abundant in Stau1(55)-containing complexes in cells arrested in prometaphase than in asynchronous cells. Our results point out for the first time to the possibility that Stau1 participates in a mechanism of post-transcriptional regulation of gene expression that is linked to cell cycle progression in cancer cells.
Nucleic Acids Research 06/2014; · 8.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: SALM Sainte-Rose is a facility set up in Reunion Island to facilitate
capacity building for research work by Moon and Mars explorers. In the
2012 programme, rock sample analysis simulations will be made in
connexion with the ILEWG Euro Moon Mars Missions at MDRS. Following
guidelines prepared by VU Amsterdam, rock samples will be taken in the
Mars-like environment near MDRS and sent to SALM to be investigated for
biological content by a team of professors and students of Reunion
University. While the result is predictable, the researchers will rather
focus on the conditions of the analysis process, avoiding contamination,
making best use of available laboratory resources, looking for "rare"
traces of life on the samples, and reflecting on a systemic approach for
life search on Mars.
[Show abstract][Hide abstract] ABSTRACT: Human immunodeficiency virus type 1 (HIV-1) requires the sequential activities of virus-encoded proteins during replication. The activities of several host cell proteins and machineries are also critical to the completion of virus assembly and the release of infectious virus particles from cells. One of these proteins, the double-stranded RNA-binding protein Staufen1 (Stau1), selectively associates with the HIV-1 genomic RNA and the viral precursor Gag protein, pr55Gag. In this report, we tested whether Stau1 modulates pr55Gag assembly using a new and specific pr55Gag oligomerization assay based on bioluminescence resonance energy transfer (BRET) in both live cells and extracts after cell fractionation. Our results show that both the overexpression and knockdown of Stau1 increase the pr55Gag-pr55Gag BRET levels, suggesting a role for Stau1 in regulating pr55Gag oligomerization during assembly. This effect of Stau1 on pr55Gag oligomerization was observed only in membranes, a cellular compartment in which pr55Gag assembly primarily occurs. Consistently, expression of Stau1 harboring a vSrc myristylation signal led to a 6.5-fold enrichment of Stau1 in membranes and a corresponding enhancement in the Stau1-mediated effect on pr55Gag-pr55Gag BRET, demonstrating that Stau1 acts on assembly when targeted to membranes. A role for Stau1 in the formation of particles is further supported by the detection of membrane-associated detergent-resistant pr55Gag complexes and the increase of virus-like particle release when Stau1 expression levels are modulated. Our results indicate that Stau1 influences HIV-1 assembly by modulating pr55Gag-pr55Gag interactions, as shown in a live cell interaction assay. This likely occurs when Stau1 interacts with membrane-associated assembly intermediates.
Journal of Virology 07/2007; 81(12):6216-30. · 5.08 Impact Factor