Regulation of Cellular RNA Nano-Particle Assembly by Splicing Factor SRp20

Abstract

Cellular RNA nano-particles (RNA granules) such as stress granule (SG) and P-body (PB) are translationally silenced mRNA-protein complexes. Previously, a genome-wide loss-of-function screen using oligomeric siRNAs targeting potential drug target genes was performed to identify genes that are involved in SG and PB assembly. SRp20 (SRSF3), a splicing regulator, was identified as a potential regulator for the RNA granule assembly. Here, we show that SRp20 is a bona-fide RNA granule component using antibody against SRp20 as well as Flag-tagged SRp20 through immunofluorescence microscopy. More importantly, upon knockdown of SRp20 using siRNA, RNA granule formation was potently disrupted indicating that SRp20 is one of the major structural components of SGs and PBs. Interestingly, polysome profiling analyses displayed that SRp20 is distributed in all ribosomal fractions suggesting a potential role of SRp20 as a post-transcriptional mRNA regulator. These results broaden the functional role of SRp20 from the nuclear RNA processing events to the cytoplasmic post-transcriptional mRNA regulatory events through RNA granules that are critical for the regulation of gene expression.

Degradation of splicing factor SRSF3 contributes to progressive liver disease

“…We found that PA-induced stress led to neddylation of SRSF3 and degradation. A previous study investigating the formation of stress granules in U2OS cells reported that the neddylation enzyme UBE2M was essential for granule formation in response to arsenite, and furthermore showed through proteomic profiling that SRSF3 was neddylated on lysine 85 to promote stress granule assembly, as they had previously reported (25,55). Our results showed that SRSF3 is neddylated on lysine 11 under PA-induced oxidative stress but this modification targeted SRSF3 for degradation.…”

Splicing factor SRSF3 represses the translation of programmed cell death 4 mRNA by associating with the 5′-UTR region

“…13 SR proteins such as SRSF1 and SRSF3 shuttle between the nucleus and the cytoplasm and migrate into RNA granules, such as PBs and stress granules (SGs), where translationally silenced mRNAs and regulatory proteins are deposited. [24][25][26] These RNA granules harbor both mRNAs that have disassembled from translationally active polysomes and proteins including a eukaryotic translation initiation factor 4E (eIF4E), XRN1 (5 0 -3 0 exonuclease), FAST (Fas-activated serine/threonine kinase), TTP (tristetraprolin), and, notably, Argonaute, a key component of RISC (RNA-induced silencing complex), a complex involved in miRNA-mediated translational repression. 27,28 We show that SRSF3 and PDCD4 mRNA are colocalized to PBs.…”

Complexity of the Alternative Splicing Landscape in Plants

“…In plants, SR proteins have been investigated for their function in splicing (Lopato et al, 1999a(Lopato et al, , 1999b. In animal systems, SR proteins, apart from their role in pre-mRNA splicing, function in diverse processes associated with RNA metabolism and gene regulation, including mRNA export, stability and translation, chromatin binding, transcription elongation, subcellular localization of transcripts, genome stability and formation of cellular RNA granules, and miRNA processing structures (stress granules and processing bodies) (Long and Caceres, 2009;Shepard and Hertel, 2009;Risso et al, 2012;Yoon et al, 2013). Whether plant SR proteins, like their animal counterparts, have wide-ranging roles in other aspects of RNA metabolism remains to be seen.…”