Expression and Functional Significance of Mouse Paraspeckle Protein 1 on Spermatogenesis1

Abstract

Paraspeckle protein 1 (PSP1) in humans is a recently identified component protein of a novel nuclear body, paraspeckle. The protein has a DBHS (Drosophila behavior, human splicing) motif that is found in PSF and p54(nrb)/NonO proteins. These DBHS-containing proteins have been reported to be involved in various nuclear events such as DNA replication, transcription, and mRNA processing. Here we show that mouse paraspeckle protein 1 (mPSP1; encoded by the Pspc1 gene) has two isoforms with different C-termini lengths. Abundant expression of the longer isoform (mPSP1-alpha) and the shorter one (mPSP1-beta) were observed in testis and kidney, respectively. Transiently expressed mPSP1-alpha was localized in nuclei, but mPSP1-beta was localized in both nuclei and cytoplasm. These observations suggest that alternative splicing regulates tissue distribution and subcellular localization. Like other DBHS-containing proteins, mPSP1 has RNA-binding activity. In mouse testis, mPSP1-alpha was found in the nuclear matrix fraction. Furthermore, by coimmunoprecipitation, we confirmed that mPSP1 interacts with other DBHS-containing proteins, PSF and p54(nrb)/NonO. Therefore, we conclude that mPSP1 may regulate multiple phases of important nuclear events during spermatogenesis.

Splicing Speckles Are Not Reservoirs of RNA Polymerase II, but Contain an Inactive Form, Phosphorylated on Serine2Residues of the C-Terminal Domain

“…Paraspeckles Are Not Sites of Transcription but Are Stably Associated with Pol II A Paraspeckles are marked by PSP1 and PSP2 proteins, which interact with CTD-binding proteins, such as p54nrb and PSF, and are found at the periphery of splicing speckles (Emili et al, 2002;Fox et al, 2002Fox et al, , 2005Kameoka et al, 2004;Myojin et al, 2004), where active genes are also associated. We tested whether paraspeckles contain pol II or are sites of transcription and found that they contain the Ser 5 P form of pol II but little of the Ser 2 P form or newly made Br-RNA ( Figure 6).…”

“…Speckles are often found spatially associated with "paraspeckle" domains, which are marked by paraspeckle proteins (PSPs) 1 and 2 (Fox et al, 2002). The protein content of paraspeckles suggests that they are involved in RNA synthesis or processing; PSPs interact with the splicing and transcription factor-associated proteins p54nrb/NonO and PSF, respectively, which in turn interact with pol II (Emili et al, 2002;Kameoka et al, 2004;Myojin et al, 2004;Fox et al, 2005). The discovery that the association of splicing factors and polyA ϩ RNA with speckles is highly dynamic has suggested that these domains are metastable compartments (Kruhlak et al, 2000;Phair and Misteli, 2000;Molenaar et al, 2004).…”

RNA-binding protein PSPC1 promotes the differentiation-dependent nuclear export of adipocyte RNAs

“…Morphological differentiation, as assessed by Oil Red O staining, was impaired in cells with reduced PSPC1 expression ( Figure 1H). Reduced expression of PSPC1 was functions of PSPC1, although it has been suggested to be important for spermatogenesis (26,27). Whether and how PSPC1 may play a role in RNA processing is unknown.…”

Paraspeckles

“…Within HeLa cells, PSPC1 is much less abundant than PSF and P54NRB (Fox et al 2005), and knockdown of PSPC1 does not affect paraspeckles in these cells (Sasaki et al 2009). Reciprocal protein-protein interactions have been reported between members of this family, and it is likely in vivo they are found as either homo or heterodimers (Myojin et al 2004;Fox et al 2005). PSPC1 and P54NRB interact via their coiled-coil domains, and, given the sequence similarity, it is likely that PSF also interacts through this domain.…”