P54nrb forms a heterodimer with PSP1 that localizes to paraspeckles in an RNA-dependent manner

Division of Gene Regulation and Expression, Wellcome Trust Biocentre, University of Dundee, Dundee DD1 5EH, United Kingdom.
Molecular Biology of the Cell (Impact Factor: 4.47). 12/2005; 16(11):5304-15. DOI: 10.1091/mbc.E05-06-0587
Source: PubMed


P54nrb is a protein implicated in multiple nuclear processes whose specific functions may correlate with its presence at different nuclear locations. Here we characterize paraspeckles, a subnuclear domain containing p54nrb and other RNA-binding proteins including PSP1, a protein with sequence similarity to p54nrb that acts as a marker for paraspeckles. We show that PSP1 interacts in vivo with a subset of the total cellular pool of p54nrb. We map the domain within PSP1 that is mediating this interaction and show it is required for the correct localization of PSP1 to paraspeckles. This interaction is necessary but not sufficient for paraspeckle targeting by PSP1, which also requires an RRM capable of RNA binding. Blocking the reinitiation of RNA Pol II transcription at the end of mitosis with DRB prevents paraspeckle formation, which recommences after removal of DRB, indicating that paraspeckle formation is dependent on RNA Polymerase II transcription. Thus paraspeckles are the sites where a subset of the total cellular pool of p54nrb is targeted in a RNA Polymerase II-dependent manner.

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    • "For ex- ample,Mao et al., demonstratedthat the lncRNA Mem ε/β was required for the recruitment of specific protein and RNA molecules to paraspeckles[77]. Additionally, immobilization of PSP1, a modular, paraspeckle protein shown to homo-and hetero-oligomerize[18], was able to recruit some paraspeckle protein components, but was unable to recapitulate complete assembly of the or- ganelle[77]. Recruitment of the full complement of protein and RNA components of paraspeckles, coupled with exclusion of macromolecules associated with nuclear speckles, was achieved only under conditions of active transcription of the Mem ε/β lncRNA. "
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    • "Beyond retaining RNAs in the nucleus [116] [117], paraspeckles have been proposed to regulate transcription (for example, via the sequestration of key transcription factors) [101] [119] [120], to control alternative splicing patterns [121], and to modulate the DNA damage response [122]. Interestingly, RNase A treatment disrupts the structural integrity of paraspeckles [117] [123], and it is now clear that MEN ε/β are the critical RNAs responsible for the biogenesis and maintenance of these nuclear structures [10] [98] [111] [112] [124] [125]. In fact, paraspeckles generally co-localize with the MEN ε/β gene loci, and inducing MEN ε/β expression is sufficient for the co-transcriptional assembly of paraspeckles [124]. "
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    • "In addition, a number of proteins were identified that were unique to this study including paraspeckle protein 1 (PSPC1), symplekin, FIP1, and nucleophosmin. PSPC1 is a component of a novel subnuclear compartment named paraspeckle and was previously shown to interact with NONO via its coiled-coil domain (Fox et al. 2005). PSPC1 and SFPQ and have also been shown to be coexpressed and interact with Sertoli cells (Kuwahara et al. 2006). "
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