Coilin interacts with Ku proteins and inhibits in vitro non-homologous DNA end joining

AbstractCoilin is a nuclear protein that plays a role in Cajal body formation. The function of nucleoplasmic coilin is unknown. Here we report that coilin interacts with Ku70 and Ku80, which are major players in the DNA repair process. Ku proteins compete with SMN and SmB′ proteins for coilin interaction sites. The binding domain on coilin for Ku proteins cannot be localized to one discrete region, and only full-length coilin is capable of inhibiting in vitro non-homologous DNA end joining (NHEJ). Since Ku proteins do not accumulate in CBs, these findings suggest that nucleoplasmic coilin participates in the regulation of DNA repair.Structured summaryMINT-8052983:coilin (uniprotkb:P38432) physically interacts (MI:0915) with SmB′ (uniprotkb:P14678) by pull down (MI:0096)MINT-8052941:coilin (uniprotkb:P38432) physically interacts (MI:0915) with Ku70 (uniprotkb:P12956) by competition binding (MI:0405)MINT-8052765:coilin (uniprotkb:P38432) physically interacts (MI:0915) with Ku80 (uniprotkb:P13010) by pull down (MI:0096)MINT-8052971:coilin (uniprotkb:P38432) physically interacts (MI:0915) with SMN (uniprotkb:Q16637) by pull down (MI:0096)MINT-8052957:coilin (uniprotkb:P38432) physically interacts (MI:0915) with Ku80 (uniprotkb:P13010) by competition binding (MI:0405)MINT-8052894, MINT-8052908:coilin (uniprotkb:P38432) binds (MI:0407) to Ku80 (uniprotkb:P13010) by pull down (MI:0096)MINT-8052804:coilin (uniprotkb:P38432) physically interacts (MI:0915) with Ku80 (uniprotkb:P13010) by anti bait coimmunoprecipitation (MI:0006)MINT-8052925:coilin (uniprotkb:P38432) binds (MI:0407) to Ku70 (uniprotkb:P12956) by pull down (MI:0096)MINT-8052786:Ku80 (uniprotkb:P13010) physically interacts (MI:0914) with coilin (uniprotkb:P38432) and Ku70 (uniprotkb:P12956) by anti bait coimmunoprecipitation (MI:0006)MINT-8052776:coilin (uniprotkb:P38432) physically interacts (MI:0915) with Ku70 (uniprotkb:P12956) by pull down (MI:0096

Coilin levels modulate cell cycle progression and γH2AX levels in etoposide treated U2OS cells

AbstractCoilin is considered the Cajal body (CB) marker protein. In this report, we investigated the role of coilin in the DNA damage response and found that coilin reduction correlated with significantly increased levels of soluble γH2AX in etoposide treated U2OS cells. Additionally, coilin levels influenced the proliferation rate and cell cycle distribution of cells exposed to etoposide. Moreover, coilin overexpression inhibited nucleolar localization of endogenous coilin in etoposide treated U2OS cells. Collectively, these data provide additional evidence for coilin and CBs in the DNA damage response

Coilin Phosphomutants Disrupt Cajal Body Formation, Reduce Cell Proliferation and Produce a Distinct Coilin Degradation Product

Coilin is a nuclear phosphoprotein that accumulates in Cajal bodies (CBs). CBs participate in ribonucleoprotein and telomerase biogenesis, and are often found in cells with high transcriptional demands such as neuronal and cancer cells, but can also be observed less frequently in other cell types such as fibroblasts. Many proteins enriched within the CB are phosphorylated, but it is not clear what role this modification has on the activity of these proteins in the CB. Coilin is considered to be the CB marker protein and is essential for proper CB formation and composition in mammalian cells. In order to characterize the role of coilin phosphorylation on CB formation, we evaluated various coilin phosphomutants using transient expression. Additionally, we generated inducible coilin phosphomutant cell lines that, when used in combination with endogenous coilin knockdown, allow for the expression of the phosphomutants at physiological levels. Transient expression of all coilin phosphomutants except the phosphonull mutant (OFF) significantly reduces proliferation. Interestingly, a stable cell line induced to express the coilin S489D phosphomutant displays nucleolar accumulation of the mutant and generates a N-terminal degradation product; neither of which is observed upon transient expression. A N-terminal degradation product and nucleolar localization are also observed in a stable cell line induced to express a coilin phosphonull mutant (OFF). The nucleolar localization of the S489D and OFF coilin mutants observed in the stable cell lines is decreased when endogenous coilin is reduced. Furthermore, all the phosphomutant cells lines show a significant reduction in CB formation when compared to wild-type after endogenous coilin knockdown. Cell proliferation studies on these lines reveal that only wild-type coilin and the OFF mutant are sufficient to rescue the reduction in proliferation associated with endogenous coilin depletion. These results emphasize the role of coilin phosphorylation in the formation and activity of CBs

Oxidative Stress and DNA Damage Induced by Chromium in Liver and Kidney of Goldfish,

Chromium (Cr) is an abundant element in the Earth's crust. It exhibits various oxidation states, from divalent to hexavalent forms. Cr has diverse applications in various industrial processes and inadequate treatment of the industrial effluents leads to the contamination of the surrounding water resources. Hexavalent chromium (Cr (VI)) is the most toxic form, and its toxicity has been associated with oxidative stress. The present study was designed to investigate the toxic potential of Cr (VI) in fish. In this research, we investigated the role of oxidative stress in chromium-induced genotoxicity in the liver and kidney cells of goldfish, Carassius auratus . Goldfish were acclimatized to the laboratory conditions and exposed them to 5% and 10% of 96 hr-LC 50 (85.7 mg/L) of aqueous Cr (VI) in a continuous flow through system. Fish were sampled every 7 days for a period of 28 days to analyze the lipid hydroperoxides (LHP) levels and genotoxic potentials in the liver and kidney. LHP levels were analyzed by spectrophotometry while genotoxicity was assessed by single cell gel electrophoresis (comet) assay. LHP levels in the liver increased significantly at week 1, followed by a decrease. LHP levels in the kidney increased significantly at weeks 1, 2, and 3, and decreased at week 4 compared to the control. The percentage of DNA damage increased in both liver and kidney at both test concentrations. The results clearly indicate that Cr (VI) induces significant levels of DNA damage in liver and kidney cells of goldfish. The induced LHP levels in both organs were concentration-dependent and were directly correlated with the levels of DNA damage. The two tested Cr (VI) concentrations induced significant levels of oxidative stress in both organs, however the kidney appears to be more vulnerable and sensitive to Cr-induced toxicity than the liver

Low Doses of Cisplatin Induce Gene Alterations, Cell Cycle Arrest, and Apoptosis in Human Promyelocytic Leukemia Cells

Cisplatin is a known antitumor drug, but its mechanisms of action are not fully elucidated. In this research, we studied the anticancer potential of cisplatin at doses of 1, 2, or 3 μM using HL-60 cells as a test model. We investigated cisplatin effects at the molecular level using RNA sequencing, cell cycle analysis, and apoptotic assay after 24, 48, 72, and 96 hours of treatment. The results show that many genes responsible for molecular and cellular functions were significantly altered. Cisplatin treatment also caused the cells to be arrested at the DNA synthesis phase, and as the time increases, the cells gradually accumulated at the sub-G1 phase. Also, as the dose increases, a significant number of cells entered into the apoptotic and necrotic stages. Altogether, the data show that low doses of cisplatin significantly impact the viability of HL-60 cells, through modulation of gene expression, cell cycle, and apoptosis

Expression of GFP-coilin and GFP coilin phosphomutant proteins in endogenous coilin depleted stable cell lines.

<p>(A and B) Stable cell lines were transfected with coilin siRNA (+) to deplete endogenous coilin, or control siRNA (−). 24 h post siRNA transfection, GFP-coilin or GFP-coilin phosphomutant expression was induced with doxycycline. 24 h later (48 h post siRNA transfection) cells were harvested and lysates were subjected to SDS-PAGE followed by western transfer and probing with anti-GFP antibodies (upper panel). The blots were then probed with anti-coilin antibodies (middle panel) followed by detection of beta-tubulin with anti-beta-tubulin antibodies (lower panel). KD – and + indicates transfection with control siRNA or coilin siRNA, respectively. Note that the GFP-coilin ON signal was too low to be detected with anti-GFP antibodies and could only be detected with anti-coilin antibodies (A, lanes 5 and 6).</p

Coilin association with Box C/D scaRNA suggests a direct role for the Cajal body marker protein in scaRNP biogenesis

Spliceosomal small nuclear ribonucleoproteins (snRNPs) are enriched in the Cajal body (CB). Guide RNAs, known as small Cajal body-specific RNAs (scaRNAs), direct modification of the small nuclear RNA (snRNA) component of the snRNP. The protein WRAP53 binds a sequence motif (the CAB box) found in many scaRNAs and the RNA component of telomerase (hTR) and targets these RNAs to the CB. We have previously reported that coilin, the CB marker protein, associates with certain non-coding RNAs. For a more comprehensive examination of the RNAs associated with coilin, we have sequenced the RNA isolated from coilin immunocomplexes. A striking preferential association of coilin with the box C/D scaRNAs 2 and 9, which lack a CAB box, was observed. This association varied by treatment condition and WRAP53 knockdown. In contrast, reduction of WRAP53 did not alter the level of coilin association with hTR. Additional studies showed that coilin degrades/processes scaRNA 2 and 9, associates with active telomerase and can influence telomerase activity. These findings suggest that coilin plays a novel role in the biogenesis of box C/D scaRNPs and telomerase

Characterization of coilin phosphomutant localization in endogenous coilin reduced stable cell lines.

<p>GFP-coilin and GFP-coilin phosphomutant stable cell lines were transfected with control (Ctrl) or coilin siRNA (KD) for 24 h. 24 h of post siRNA treatment, cells were treated with doxycycline and incubated for another 24 h. The 48 h siRNA transfected and 24 h doxycycline induced stable cell lines were fixed, extracted and immunostained for SMN (red). Nuclei were stained with DAPI (blue). Arrows mark some canonical CBs (containing coilin and SMN). Double arrows mark SMN foci that lack coilin (Gems). Single arrowheads indicate nucleolar coilin accumulation. Double arrowheads mark coilin foci that do not have significant enrichment of SMN, and triple arrowheads indicate dim micro-CB structures. Note that the GFP-coilin ON signal was difficult to detect after the siRNA transfection protocol, so polyclonal GFP antibodies were used to amplify this signal. Scale bars 10 µm.</p

Characterization of doxycycline inducible coilin phosphomutant cell lines.

<p>(A and B) Stable cell lines expressing GFP-coilin of GFP-coilin phosphomutant proteins. Non-induced (−) and 24 h doxycycline induced (1 µg/mL, +) cell lysates of GFP-coilin (WT) and GFP-coilin phosphomutants (T122E, ON, S489D, S271/272D or OFF) were subjected to SDS-PAGE, followed by western transfer. The blots were probed with mouse monoclonal anti-GFP antibodies for specific detection of the GFP-tagged coilin proteins (upper panel). The blots were re-probed with rabbit polyclonal anti-coilin antibodies to detect both endogenous coilin and the GFP-tagged WT and coilin phosphomutants (lower panel). Note that S489D and OFF expression generates an approximately 42 kDa degradation product. (C) Transiently transfected GFP-coilin S489D and GFP-coilin OFF phosphomutant proteins do not have a specific degradation product. HeLa cells were transiently transfected with GFP-coilin S489D and GFP-coilin OFF DNA constructs for 24 h followed by lysate generation, SDS-PAGE and western transfer. The blot was probed with antibodies to GFP. (D) Full length GFP-coilin S489D can be detected after doxycycline induction by immunoprecipitation. Doxycycline (0.33 or 1 µg/mL) induced and non-induced GFP-coilin-S489D stable cell extracts were immunoprecipitated with anti-GFP antibodies. The western blot was probed with anti-GFP antibodies for the detection of the GFP-coilin-S489D fragment (upper panel). The same blot was probed with anti-coilin antibodies for endogenous coilin and full length GFP-coilin-S489D protein detection (lower panel). IgG(H) denotes the immunoglobulin heavy chain.</p