A conformational study of a glutamine- and proline-rich cereal seed protein, C hordein.
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ABSTRACT:
SUBMITTER: Tatham AS
PROVIDER: S-EPMC1144744 | biostudies-other | 1985 Mar
REPOSITORIES: biostudies-other
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Project description:Huntington's disease is a progressive neurodegenerative disease caused by a polyglutamine (polyQ) repeat expansion in the huntingtin protein [Huntington's Disease Collaborative Research Group (1993) Cell 72, 971-983]. To understand the mechanism by which polyQ repeats cause neurodegeneration and cell death, we modeled polyQ neurotoxicity in Caenorhabditis elegans. In our model, expression of N-terminal fragments of human huntingtin causes polyQ-dependent degeneration of neurons. We conducted a genetic screen to identify proteins that protect neurons from the toxic effects of expanded polyQ tracts. Loss of polyQ enhancer-1 (pqe-1) gene function strongly and specifically exacerbates neurodegeneration and cell death, whereas overexpression of a pqe-1 cDNA protects C. elegans neurons from the toxic effects of expanded huntingtin fragments. A glutamineproline-rich domain, along with a charged domain, is critical for PQE-1 protein function. Analysis of pqe-1 suggests that proteins exist that specifically protect neurons from the toxic effects of expanded polyQ disease proteins.
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Project description:The influenza A virus RNA polymerase is a heterotrimeric complex responsible for viral genome transcription and replication in the nucleus of infected cells. We recently carried out a proteomic analysis of purified polymerase expressed in human cells and identified a number of polymerase-associated cellular proteins. Here we characterise the role of one such host factors, SFPQ/PSF, during virus infection. Down-regulation of SFPQ/PSF by silencing with two independent siRNAs reduced the virus yield by 2-5 log in low-multiplicity infections, while the replication of unrelated viruses as VSV or Adenovirus was almost unaffected. As the SFPQ/PSF protein is frequently associated to NonO/p54, we tested the potential implication of the latter in influenza virus replication. However, down-regulation of NonO/p54 by silencing with two independent siRNAs did not affect virus yields. Down-regulation of SFPQ/PSF by siRNA silencing led to a reduction and delay of influenza virus gene expression. Immunofluorescence analyses showed a good correlation between SFPQ/PSF and NP levels in infected cells. Analysis of virus RNA accumulation in silenced cells showed that production of mRNA, cRNA and vRNA is reduced by more than 5-fold but splicing is not affected. Likewise, the accumulation of viral mRNA in cicloheximide-treated cells was reduced by 3-fold. In contrast, down-regulation of SFPQ/PSF in a recombinant virus replicon system indicated that, while the accumulation of viral mRNA is reduced by 5-fold, vRNA levels are slightly increased. In vitro transcription of recombinant RNPs generated in SFPQ/PSF-silenced cells indicated a 4-5-fold reduction in polyadenylation but no alteration in cap snatching. These results indicate that SFPQ/PSF is a host factor essential for influenza virus transcription that increases the efficiency of viral mRNA polyadenylation and open the possibility to develop new antivirals targeting the accumulation of primary transcripts, a very early step during infection.
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Project description:Splicing factor proline-glutamine rich (SFPQ), a multifunctional RNA-binding protein (RBP), shows cytoplasmic colocalisation with stress granule (SG) markers; however, the causative relationship and mechanism underlying this coalescence of SFPQ aggregates and SGs remain unclear. In this study, we demonstrate that SFPQ lacking its nuclear localisation sequence spontaneously forms cytoplasmic aggregates that abnormally incorporate immature RNA and induce persistent SGs. mRNA profiling showed that SFPQ mislocalisation induced extensive changes in RNA processing, with a subset of alternatively spliced transcripts associated with nucleocytoplasmic transport. Notably, these altered transporters were sequestered into SFPQ aggregates, constituting aberrant protein-RNA complexes. Importantly, suppression of SG nucleation could not block cytoplasmic SFPQ aggregation with immature RNA and nucleocytoplasmic transporters, both of which, however, were moderately ameliorated by the inhibition of alternative splicing or nuclear export. Our results unveil the physiopathological role and mechanism for mislocalised SFPQ in the RNA metabolism, nucleocytoplasmic transport and pathological SGs.
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