Abstract:Heterogeneous nuclear ribonucleoproteins (hnRNPs) comprise a family of RNA-binding proteins. The complexity and diversity associated with the hnRNPs render them multifunctional, involved not only in processing heterogeneous nuclear RNAs (hnRNAs) into mature mRNAs, but also acting as trans-factors in regulating gene expression. Heterogeneous nuclear ribonucleoprotein E1 (hnRNP E1), a subgroup of hnRNPs, is a KH-triple repeat containing RNA-binding protein. It is encoded by an intronless gene arising from hnRNP … Show more
“…Our investigation extends the multiple capacity of PCBP1 [43,44] as an E3 ubiquitin ligase adaptor for housekeeping degradation of MAVS [45,46]. Besides, PCBP1 displays some regulatory effects after viral infection ( Figures 3D and 6).…”
Section: Discussionsupporting
confidence: 71%
“…The unique property of PCBP1 was observed in knockdown studies that point to a housekeeping role for PCBP1 at the quiescent state ( Figure 6). This specificity may serve as another sound piece of evidence for divergent physiological functions of the two proteins as reported elsewhere [40][41][42][43].…”
Mitochondrial antiviral signaling (MAVS) is a key adaptor in cellular antiviral innate immunity. We previously identified poly(C)-binding protein 2 (PCBP2) as a feedback inhibitor of MAVS that facilitates its degradation after viral infection, but little is known about the regulatory potential of poly(C)-binding protein 1 (PCBP1), which highly resembles PCBP2. Here we report that PCBP1 mediates housekeeping degradation of MAVS using the same mechanism as PCBP2 employs. Overexpression of PCBP1 impairs MAVS-mediated antiviral responses, while knockdown of PCBP1 exerts the opposite effect. The suppression is due to PCBP1-induced MAVS degradation. We observe that PCBP1 and PCBP2 show synergy in MAVS inhibition, but their expression patterns are distinct: PCBP1 is stably and abundantly expressed, while PCBP2 shows low basal expression with rapid induction after infection. Individual knockdown and subcellular fractionation analyses reveal that unlike the postinfection inhibitor PCBP2, PCBP1 continuously eliminates cellular MAVS. Our findings unravel a critical role of PCBP1 in regulating MAVS for both finetuning the antiviral immunity and preventing inflammation.
“…Our investigation extends the multiple capacity of PCBP1 [43,44] as an E3 ubiquitin ligase adaptor for housekeeping degradation of MAVS [45,46]. Besides, PCBP1 displays some regulatory effects after viral infection ( Figures 3D and 6).…”
Section: Discussionsupporting
confidence: 71%
“…The unique property of PCBP1 was observed in knockdown studies that point to a housekeeping role for PCBP1 at the quiescent state ( Figure 6). This specificity may serve as another sound piece of evidence for divergent physiological functions of the two proteins as reported elsewhere [40][41][42][43].…”
Mitochondrial antiviral signaling (MAVS) is a key adaptor in cellular antiviral innate immunity. We previously identified poly(C)-binding protein 2 (PCBP2) as a feedback inhibitor of MAVS that facilitates its degradation after viral infection, but little is known about the regulatory potential of poly(C)-binding protein 1 (PCBP1), which highly resembles PCBP2. Here we report that PCBP1 mediates housekeeping degradation of MAVS using the same mechanism as PCBP2 employs. Overexpression of PCBP1 impairs MAVS-mediated antiviral responses, while knockdown of PCBP1 exerts the opposite effect. The suppression is due to PCBP1-induced MAVS degradation. We observe that PCBP1 and PCBP2 show synergy in MAVS inhibition, but their expression patterns are distinct: PCBP1 is stably and abundantly expressed, while PCBP2 shows low basal expression with rapid induction after infection. Individual knockdown and subcellular fractionation analyses reveal that unlike the postinfection inhibitor PCBP2, PCBP1 continuously eliminates cellular MAVS. Our findings unravel a critical role of PCBP1 in regulating MAVS for both finetuning the antiviral immunity and preventing inflammation.
“…We also observed removal of PCBP1 protein from telomere after treatment with SWNTs. However, up to now, the real mechanism for PCBP1 protein on telomere regulation has not been fully illustrated 54 , and substantial works are currently needed. Our confocal microscope, ChIP and reciprocal IP results demonstrate that PCBP1 can localize at telomere and interact with TRF1 and TRF2 proteins (Fig.…”
Both human telomeric G-rich and C-rich DnA have been considered as specific drug targets for cancer therapy. However, due to i-motif structure instability and lack of specific binding agents, it remains unclear whether stabilization of telomeric i-motif can inhibit telomerase activity. single-walled carbon nanotubes (sWnTs) have been reported as the first ligand that can selectively stabilize human telomeric i-motif DnA. Here we report that sWnTs can inhibit telomerase activity through stabilization of i-motif structure. The persistence of i-motif and the concomitant G-quadruplex eventually leads to telomere uncapping and displaces telomerebinding proteins from telomere. The dysfunctional telomere triggers DnA damage response and elicits upregulation of p16 and p21 proteins. This is the first example that sWnTs can inhibit telomerase activity and interfere with the telomere functions in cancer cells. These results provide new insights into understanding the biomedical effects of sWnTs and the biological importance of i-motif DnA.
“…In particular, the mammalian hnRNP family consists of at least 24 structurally diverse polypeptides (6). SR proteins constitute a family of about twelve evolutionarily conserved polypeptides (7) that contain one or two N-terminal RNA-recognition motifs (RRMs) and a region of variable length that is enriched in Arg-Ser dipeptides (RS domain).…”
Section: Splicing and Alternative Splicingmentioning
SummarySerine/arginine-rich (SR) proteins are among the most studied splicing regulators. They constitute a family of evolutionarily conserved proteins that, apart from their initially identified and deeply studied role in splicing regulation, have been implicated in genome stability, chromatin binding, transcription elongation, mRNA stability, mRNA export and mRNA translation. Remarkably, this list of SR protein activities seems far from complete, as unexpected functions keep being unraveled. An intriguing aspect that awaits further investigation is how the multiple tasks of SR proteins are concertedly regulated within mammalian cells. In this article, we first discuss recent findings regarding the regulation of SR protein expression, activity and accessibility. We dive into recent studies describing SR protein auto-regulatory feedback loops involving different molecular mechanisms such as unproductive splicing, microRNA-mediated regulation and translational repression. In addition, we take into account another step of regulation of SR proteins, presenting new findings about a variety of post-translational modifications by proteomics approaches and how some of these modifications can regulate SR protein sub-cellular localization or stability. Towards the end, we focus in two recently revealed functions of SR proteins beyond mRNA biogenesis and metabolism, the regulation of micro-RNA processing and the regulation of small ubiquitin-like modifier (SUMO) conjugation.
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