Evaluation of Phototoxicity of Short-Wavelength Laser Light Utilizing PCNA Accumulation

In recent years, diseases such as age-related macular degeneration and retinal pigment degeneration caused by excessive exposure to short-wavelength visible light have become significant concerns. With the aim of quantitatively evaluating the toxicity of short-wavelength light, proliferating cell nuclear antigen (PCNA) accumulation at the irradiation site was investigated using live cell imaging techniques to irradiate individual living cells with short-wavelength laser light. By examining the dependency of PCNA accumulation on the irradiation site within the cells and their cell cycle, it was observed that PCNA accumulation occurred only when the cell nucleus of cells in the S phase of the cell cycle was irradiated. We investigated the accumulation of PCNA at the laser irradiation site using laser light at wavelengths of 405 nm and 375 nm, with intensities ranging from 0.5 μW to 9.0 μW. The results confirmed an increase in PCNA accumulation with increasing intensity, and a higher accumulation was observed with laser light irradiation at a wavelength of 375 nm compared to 405 nm. By comparing the PCNA accumulation and 24 h cell viability, we demonstrated the feasibility of quantitatively assessing laser light toxicity through the measurement of PCNA accumulation.

Ehrlich ascites carcinoma provokes renal toxicity and DNA injury in mice: Therapeutic impact of chitosan and maitake nanoparticles

In this study, the impact of chitosan (CS) and maitake (GF) nanoparticles towards the renal toxicity induced by Ehrlich ascites carcinoma (EAC) in vivo model was conducted. Besides benchmark negative control group, EAC model was constructed by intraperitoneal injection (i.p.) of 2.5 × 106 cells. Alongside positive control, two groups of EAC-bearing mice received 100 mg/kg of CS and GF nanoparticles/body weight daily for 14 days. The kidney function was conducted by measuring urea, creatinine, ions, (anti)/oxidative parameters and DNA damage. Also, measuring immunoreactivity of P53, proliferating cell nuclear antigen (PCNA), and B-cell lymphoma 2 (Bcl-2) and apoptosis protein. The outcomes illustrated notable kidney toxicity, which indicated by elevations in urea, creatinine, oxidative stress, DNA damage and induction of apoptosis. These events were supported by the drastic alteration in kidney structure through histological examination. Administration of CS and GF nanoparticles was able to enhance the antioxidant power, which further reduced oxidative damage, DNA injury, and apoptosis. These results indicated the protective and therapeutic role of biogenic chitosan and maitake nanoparticles against nephrotoxicity.

Evaluation of mutations on O6-methylguanine methyl transferase structure and its interactions: molecular dynamics simulation study

O6-methylguanine DNA methyl transferase (MGMT) is a significant vehicle for the cellular clearance of alkyl lesions, particularly the methyl group of the O-6 and O-4 positions of guanine and thymine, respectively. Many publications have studied the correlation between polymorphisms in MGMT and susceptibility to various cancers. In the present study, we investigated the consequence of L84F, common single-nucleotide polymorphism, K125E, site-specific mutagenesis, and L84F/K125E on conformation, stability, and behavior of MGMT in the free form and interaction with proliferating cell nuclear antigen (PCNA) and DNA as partners in the biochemical network by using molecular dynamics simulation method. Our results showed that all free variants of MGMT differed from the native form. However, among all free variants of MGMT, the L84F/K125E variant exhibited similar properties compared with the wild-type. In contrast, in complex modes, only amino acid residues of the L84F variant are involved in the interactions with PCNA and DNA somewhat differently relative to the wild-type. Furthermore, L84F SNP showed the highest binding free energy compared to other variants and native forms. These alterations in the amino acids and binding free energy of L84F relative to the native are the reasons for changing its region connection compared to the native form. Therefore, we propose conducting further investigations into the impact of inhibitors or chemotherapeutic agents to assess their effectiveness on MGMT variants compared to the wild-type, aiming to reduce the cost of cancer treatment that will depend on inhibiting native MGMT protein.Communicated by Ramaswamy H. Sarma.

mAb14, a Monoclonal Antibody against Cell Surface PCNA: A Potential Tool for Sezary Syndrome Diagnosis and Targeted Immunotherapy

Mycosis fungoides (MF) and Sézary syndrome (SS) are the most common types of primary cutaneous T-cell lymphoma (CTCL). Proliferating cell nuclear antigen (PCNA) is expressed on the cell surface of cancer cells (csPCNA), but not on normal cells. It functions as an immune checkpoint ligand by interacting with natural killer (NK) cells through the NK inhibitory receptor NKp44, leading to the inhibition of NK cytotoxicity. A monoclonal antibody (mAb14) was established to detect csPCNA on cancer cells and block their interaction with NKp44. In this study, three CTCL cell lines and peripheral blood mononuclear cells (PBMCs) from patients with SS and healthy donors were analyzed for csPCNA using mAb14, compared to monoclonal antibody PC10, against nuclear PCNA (nPCNA). The following assays were used: immunostaining, imaging flow cytometry, flow cytometry, cell sorting, cell cycle analysis, ELISA, and the NK-cell cytotoxic assay. mAb14 successfully detected PCNA on the membrane and in the cytoplasm of viable CTCL cell lines associated with the G2/M phase. In the Sézary PBMCs, csPCNA was expressed on lymphoma cells that had an atypical morphology and not on normal cells. Furthermore, it was not expressed on PBMCs from healthy donors. In the co-culture of peripheral blood NK (pNK) cells with CTCL lines, mAb14 increased the secretion of IFN-γ, indicating the reactivation of pNK activity. However, mAb14 did not enhance the cytotoxic activity of pNK cells against CTCL cell lines. The unique expression of csPCNA detected by mAb14 suggests that csPCNA and mAb14 may serve as a potential biomarker and tool, respectively, for detecting malignant cells in SS and possibly other CTCL variants.

Micro Ribonucleic Acid-29a (miR-29a) Antagonist Normalizes Bone Metabolism in Osteogenesis Imperfecta (OI) Mice Model

Osteogenesis imperfecta (OI) is not curative nowadays. This study tried to unriddle the therapeutic potential of micro ribonucleic acid-29a (miR-29a) antagonist in treating OI in a mouse animal model (B6C3Fe a/a-Col1a2oim/J). We showed that the expression levels of miR-29a were higher in bone tissues obtained from the OI mice than from wild-type mice demonstrated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and in situ hybridization assay. We established lentivirus-shuttled vector expressing miR-29a antisense oligonucleotide (miR-29a-AS) and miR-29a precursors (pre-miR-29a), showing that the inferior bony architecture in micro-computed tomography and pertinent morphometric parameters could be rescued by miR-29a-AS and deteriorated by pre-miR-29a. The decreased proliferating cell nuclear antigen (PCNA), increased Dickkopf-1 (DKK1), and decreased β-catenin expression in OI mice could be accentuated by pre-miR-29a and normalized by miR-29a-AS. The decreased osteogenesis and increased osteoclastogenesis in OI mice could also be accentuated by pre-miR-29a and normalized by miR-29a-AS. miR-29a-AS did not seem to possess severe hepatic or renal toxicities.

Therapeutic effects of sulforaphane in ulcerative colitis: effect on antioxidant activity, mitochondrial biogenesis and DNA polymerization

Objectives

Ulcerative colitis (UC), an inflammatory bowel disease, affects mucosal lining of colon leading to inflammation and ulcers. Sulforaphane is a natural compound obtained from cruciferous vegetables. We aimed to investigate potential therapeutic effects of sulforaphane in experimentally induced UC in rats through affection antioxidant activity, mitochondrial biogenesis and DNA polymerization.

Methods

UC was induced in rats via an intracolonic single administration of 2 ml of 4% acetic acid. UC rats were treated with 15 mg/kg sulforaphane. Samples of colon were used to investigate gene expression and protein levels of peroxisome proliferator-activated receptor-gamma coactivator (PGC-1), mitochondrial transcription factor A (TFAM), mammalian target of rapamycin (mTOR), cyclin D1, nuclear factor erythroid 2-related factor-2 (Nrf2), heme Oxygenase-1 (HO-1) and proliferating cell nuclear antigen (PCNA).

Results

UC showed dark distorted Goblet cell nucleus with disarranged mucus granules and no distinct brush border with atypical microvilli. All morphological changes were improved by treating with sulforaphane. Finally, treatment with sulforaphane significantly increased expression of PGC-1, TFAM, Nrf2 and HO-1 associated with reduction in expression of mTOR, cyclin D1 and PCNA.

Conclusion

Sulforaphane could cure UC in rats. The protective activity can be explained by enhancing antioxidant activity, elevating mitochondrial biogenesis and inhibiting DNA polymerization.

Bioinformatics analysis of the prognostic biomarkers and predictive accuracy of differentially expressed genes in high-risk multiple myeloma based on Gene Expression Omnibus database mining

Background

Multiple myeloma (MM) is still an intractable disease for modern clinical system, and more researches are necessary for development of more effective therapeutic strategies. This study attempted to screen and validates the biomarkers in the progression of MM via excavating Gene Expression Omnibus (GEO) database. Identification of a biomarker may help not only facilitate early diagnosis and management but also identify individuals at risk for poor prognosis and development of MM.

Methods

The mRNA expression profile of the GSE87900 dataset was analyzed by GEO2R. Using the SangerBox online program, differentially expressed genes (DEGs) in high-risk MM samples were screened with the filter criteria of P<0.05 and |logFC| >1. The SangerBox online analysis tool was used to analyze the volcano plot. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was performed for DEGs. Twenty patients with high-risk MM and 20 patients with standard-risk MM from Taian City Central Hospital were included. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to verify the selected key genes in MM tissues.

Results

A total of 611 DEGs were obtained. GO functional enrichment analysis showed that the DEGs were mainly enriched in the DNA replication process at the biological level, and the top DEGs were CACYBP, PCNA, MCM6, SMC1A, DTL, GINS4, MCM2, CDT1, RRM2, BRCA1, RFC5, MCM4, GINS3, GINS1, MCM10, CDC7, CDAN1, BRIP1, GINS2, CDK1, NFIB, and BARD1. The expression of CDC7 and PCNA was significantly different in high-risk MM and standard-risk MM as determined by RT-qPCR. Receiver operating characteristic (ROC) analysis showed that the areas under the curve predicted by CDC7 and PCNA were 0.900 and 0.8863, respectively, which allowed the identification of CDC7 and PCNA could be a potential biomarker of MM. Kaplan-Meier survival analysis showed that MM patients with high CDC7 and PCNA expression had shorter 2-year overall survival (OS) (P<0.05).

Conclusions

CDC7 and PCNA can be used as biomarkers for the prognosis of high-risk MM and evaluate the prognosis of MM patients, which is helpful for guiding the clinical treatment of MM patients.

ROS and DNA repair in spontaneous versus agonist-induced NETosis: Context matters

Reactive oxygen species (ROS) is essential for neutrophil extracellular trap formation (NETosis). Nevertheless, how ROS induces NETosis at baseline and during neutrophil activation is unknown. Although neutrophils carry DNA transcription, replication and repair machineries, their relevance in the short-lived mature neutrophils that carry pre-synthesized proteins has remained a mystery for decades. Our recent studies show that (i) NETosis-inducing agonists promote NETosis-specific kinase activation, genome-wide transcription that helps to decondense chromatin, and (ii) excess ROS produced by NADPH oxidase activating agonists generate genome-wide 8-oxy-guanine (8-OG), and the initial steps of DNA repair are needed to decondense chromatin in these cells. These steps require DNA repair proteins necessary for the assembly and nicking at the damaged DNA sites (poly ADP ribose polymerase PARP, apurinic endonuclease APE1 and DNA ligase), but not the enzymes that mediate the repair DNA synthesis (Proliferating cell nuclear antigen (PCNA) and DNA Polymerases). In this study, we show that (i) similar to agonist-induced NETosis, inhibition of early steps of oxidative DNA damage repair proteins suppresses spontaneous NETosis, but (ii) the inhibition of late stage repair proteins DNA polymerases and PCNA drastically promotes baseline NETosis. Hence, in the absence of excessive ROS generation and neutrophil activation, DNA repair mediated by PCNA and DNA polymerases is essential to prevent chromatin decondensation and spontaneous NETosis. These findings indicate that ROS, oxidative DNA damage, transcription and DNA repair differentially regulate spontaneous and agonist-induced NETosis. Therefore, context matters.

The effects of proliferating cell nuclear antigen and p53 in patients with oral squamous cell carcinoma: a systematic review and meta-analysis

BACKGROUND

To evaluate the effect of proliferating cell nuclear antigen (PCNA) and p53 in patients with oral squamous cell carcinoma (OSCC).

METHODS

Multiple databases, including PubMed, Embase, Cochrane library, and China National Knowledge Database, were searched for relevant studies and full-text articles that evaluated the effect of PCNA and p53 in patients with OSCC. Review Manager 5.2 was adopted to estimate the impact of the results among the selected articles. Forest plots, NOS table, sensitivity analysis, and bias analysis were also conducted.

RESULTS

In total, nine eligible studies satisfied the included criteria. High PCNA expression (>50%) was significantly more prevalent in OSCC than low PCNA expression (<50%) (OR =3.88; 95% CI: 2.04-7.37; P<0.0001; I²=0%). However, there was no significant difference between p53 and OSCC (OR =1.60; 95% CI: 0.18-14.63; P=0.68; I²=86%). Low PCNA expression had a higher 5-year overall survival in OSCC patients than high PCNA expression (OR =0.47; 95% CI: 0.27-0.80; P=0.005; I²=41%). Meanwhile, p53 negative had a higher 5-year overall survival than p53 positive (OR =0.20; 95% CI: 0.10-0.42; P<0.0001; I²=0%). There was no difference between high and low PCNA in terms of metastasis (OR =0.80 with 95% CI: 0.18-3.45, I²=63%, P of over effect =0.76). The overall results showed no difference between p53 and metastasis (OR =0.38 with 95% CI: 0.13-1.10, I²=0%, P of over effect =0.07).

DISCUSSION

PCNA and p53 might be suitable for prognostic and survival evaluation in OSCC patients.

Unlocking the PIP-box: A peptide library reveals interactions that drive high-affinity binding to human PCNA

The human sliding clamp, Proliferating Cell Nuclear Antigen (hPCNA), interacts with over 200 proteins through a conserved binding motif, the PIP-box, to orchestrate DNA replication and repair. It is not clear how changes to the features of a PIP-box modulate protein binding and thus how they fine-tune downstream processes. Here, we present a systematic study of each position within the PIP-box to reveal how hPCNA-interacting peptides bind with drastically varied affinities. We synthesized a series of 27 peptides derived from the native protein p21 with small PIP-box modifications and another series of 19 peptides containing PIP-box binding motifs from other proteins. The hPCNA-binding affinity of all peptides, characterized as K_D values determined by surface plasmon resonance, spanned a 4000-fold range, from 1.83 nM to 7.59 μM. The hPCNA-bound peptide structures determined by X-ray crystallography and modeled computationally revealed intermolecular and intramolecular interaction networks that correlate with high hPCNA affinity. These data informed rational design of three new PIP-box sequences, testing of which revealed the highest affinity hPCNA-binding partner to date, with a K_D value of 1.12 nM, from a peptide with PIP-box QTRITEYF. This work showcases the sequence-specific nuances within the PIP-box that are responsible for high-affinity hPCNA binding, which underpins our understanding of how nature tunes hPCNA affinity to regulate DNA replication and repair processes. In addition, these insights will be useful to future design of hPCNA inhibitors.

Age and insulin-like growth factor-1 impact PCNA monoubiquitination in UVB-irradiated human skin

Nonmelanoma skin cancers occur primarily in individuals over the age of 60 and are characterized by an abundance of ultraviolet (UV) signature mutations in keratinocyte DNA. Though geriatric skin removes UV photoproducts from DNA less efficiently than young adult skin, it is not known whether the utilization of other prosurvival but potentially mutagenic DNA damage tolerance systems such as translesion synthesis (TLS) is altered in older individuals. Using monoubiquitination of the replicative DNA polymerase clamp protein PCNA (proliferating cell nuclear antigen) as a biochemical marker of TLS pathway activation, we find that UVB exposure of the skin of individuals over the age of 65 results in a higher level of PCNA monoubiquitination than in the skin of young adults. Furthermore, based on previous reports showing a role for deficient insulin-like growth factor-1 (IGF-1) signaling in altered UVB DNA damage responses in geriatric human skin, we find that both pharmacological inhibition of the IGF-1 receptor (IGF-1R) and deprivation of IGF-1 potentiate UVB-induced PCNA monoubiquitination in both human skin ex vivo and keratinocytes in vitro. Interestingly, though the TLS DNA polymerase Pol eta can accurately replicate the major photoproducts induced in DNA by UV radiation, we find that it fails to accumulate on chromatin in the absence of IGF-1R signaling and that this phenotype is correlated with increased mutagenesis in keratinocytes in vitro. Thus, altered IGF-1/IGF-1R signaling in geriatric skin may predispose epidermal keratinocytes to carry out a more mutagenic form of DNA synthesis following UVB exposure.

Multi-Omics Integration Highlights the Role of Ubiquitination in CCl4-Induced Liver Fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins that occurs in chronic liver disease. Ubiquitination is a post-translational modification that is crucial for a plethora of physiological processes. Even though the ubiquitin system has been implicated in several human diseases, the role of ubiquitination in liver fibrosis remains poorly understood. Here, multi-omics approaches were used to address this. Untargeted metabolomics showed that carbon tetrachloride (CCl₄)-induced liver fibrosis promotes changes in the hepatic metabolome, specifically in glycerophospholipids and sphingolipids. Gene ontology analysis of public deposited gene array-based data and validation in our mouse model showed that the biological process “protein polyubiquitination” is enriched after CCl₄-induced liver fibrosis. Finally, by using transgenic mice expressing biotinylated ubiquitin (^bioUb mice), the ubiquitinated proteome was isolated and characterized by mass spectrometry in order to unravel the hepatic ubiquitinated proteome fingerprint in CCl₄-induced liver fibrosis. Under these conditions, ubiquitination appears to be involved in the regulation of cell death and survival, cell function, lipid metabolism, and DNA repair. Finally, ubiquitination of proliferating cell nuclear antigen (PCNA) is induced during CCl₄-induced liver fibrosis and associated with the DNA damage response (DDR). Overall, hepatic ubiquitome profiling can highlight new therapeutic targets for the clinical management of liver fibrosis.

The ameliorative effect of curcumin on cryptorchid and non-cryptorchid testes in induced unilateral cryptorchidism in albino rat: histological evaluation

BACKGROUND

Cryptorchidism, one or both hidden testes, is the most common abnormality of male sexual development. Subfertility or infertility is associated with both unilateral and bilateral cryptorchidism. In this study, we investigate the possible ameliorative effect of curcumin (Cur) on the induced-unilateral cryptorchidism testicular injury in both cryptorchid (Cryp) and non-cryptorchid (non-Cryp) scrotal testes through histological, immunohistochemical and morphometrics.

MATERIALS AND METHODS

Forty adult male albino rats were divided into: control group, Cur control group, Cryp group, and Cryp+Cur group. The rat model was surgically established by fixing the left testis in the abdomen. The treated groups were subjected to surgically induced-unilateral cryptorchidism on the left side then were given Cur (80 mg/kg) orally, for 20 days. Histological analysis using haematoxylin and eosin and periodic acid Schiff's reaction was done. Immunohistochemistry was performed for proliferating cell nuclear antigen (PCNA); to estimate the proliferation in the germinal epithelium, and vimentin; to evaluate Sertoli cells. The results were confirmed by statistical evaluation of the spermatogenic epithelium height, the seminiferous tubules diameter, the basement membrane thickness, the number of PCNA immunostained cells and the area per cent of vimentin immunostaining.

RESULTS

Distorted seminiferous tubules, substantial degeneration of the germinal epithelium, thickening of the basement membrane with a significant decrease in PCNA and vimentin immunostaining were observed in Cryp group; mainly in the cryptorchid testis. These structural changes were significantly reversed in Crypt+Cur group.

CONCLUSIONS

Curcumin proved to be an important and effective medical line for protecting against the unfavourable sequels of cryptorchidism in a rat model.

Multisite SUMOylation restrains DNA polymerase η interactions with DNA damage sites

Translesion DNA synthesis (TLS) mediated by low-fidelity DNA polymerases is an essential cellular mechanism for bypassing DNA lesions that obstruct DNA replication progression. However, the access of TLS polymerases to the replication machinery must be kept tightly in check to avoid excessive mutagenesis. Recruitment of DNA polymerase η (Pol η) and other Y-family TLS polymerases to damaged DNA relies on proliferating cell nuclear antigen (PCNA) monoubiquitylation and is regulated at several levels. Using a microscopy-based RNAi screen, here we identified an important role of the SUMO modification pathway in limiting Pol η interactions with DNA damage sites in human cells. We found that Pol η undergoes DNA damage- and protein inhibitor of activated STAT 1 (PIAS1)-dependent polySUMOylation upon its association with monoubiquitylated PCNA, rendering it susceptible to extraction from DNA damage sites by SUMO-targeted ubiquitin ligase (STUbL) activity. Using proteomic profiling, we demonstrate that Pol η is targeted for multisite SUMOylation, and that collectively these SUMO modifications are essential for PIAS1- and STUbL-mediated displacement of Pol η from DNA damage sites. These findings suggest that a SUMO-driven feedback inhibition mechanism is an intrinsic feature of TLS-mediated lesion bypass functioning to curtail the interaction of Pol η with PCNA at damaged DNA to prevent harmful mutagenesis.

Structure of the RAD9-RAD1-HUS1 checkpoint clamp bound to RHINO sheds light on the other side of the DNA clamp

DNA clamp, a highly conserved ring-shaped protein, binds dsDNA within its central pore. Also, DNA clamp interacts with various nuclear proteins on its front, thereby stimulating their enzymatic activities and biological functions. It has been assumed that the DNA clamp is a functionally single-faced ring from bacteria to humans. Here, we report the crystal structure of the heterotrimeric RAD9-RAD1-HUS1 (9-1-1) checkpoint clamp bound to a peptide of RHINO, a recently identified cancer-related protein that interacts with 9-1-1 and promotes activation of the DNA damage checkpoint. This is the first structure of 9-1-1 bound to its partner. The structure reveals that RHINO is unexpectedly bound to the edge and around the back of the 9-1-1 ring through specific interactions with the RAD1 subunit of 9-1-1. Our finding indicates that 9-1-1 is a functionally double-faced DNA clamp.

Mechanistic evaluation of AMPK/SIRT1/FXR signaling axis, inflammation, and redox status in thioacetamide-induced liver cirrhosis: The role of Cichorium intybus linn (chicory)-supplemented diet

Liver cirrhosis is a scene profitable to the advance of hepatocellular carcinoma (HCC). The current work was engrossed to weigh the potential role of Cichorium intybus linn against thioacetamide (TAA)-induced liver cirrhosis and their probable underlying biochemical and molecular mechanisms. farnesoid-X-receptor (FXR) expression, proliferating cell nuclear antigen (PCNA) immunoreactivity, and activated AMP protein kinase (pAMPK), sirtuin-1 (SIRT1), and interleukin-6 (IL6) levels were estimated in hepatic tissue by real-time PCR, immunohistochemistry, and immunoassay, respectively. C. intybus linn supplementation caused a significant improvement in serum liver enzymes, albumin, bilirubin levels, tissues redox status and hepatic histological features in addition to decreased IL6 level, hydroxylproline content, and PCNA immunoreactivity. On contrary, increased pAMPK/SIRT1 levels and upregulated FXR gene expression were observed. C. intybus linn could feasibly protect against TAA-induced hepatic damage, fibrosis, and cirrhosis by relieving oxidative stress and by interruption of the inflammatory pathway via AMPK/SIRT1/FXR signaling. PRACTICAL APPLICATIONS: No specific therapies are available until now to target the underlying mechanisms for protection against liver diseases. Herbal protection is widely available and cheap with no side effect. Cichorium intybus linn, a natural supplement, is proved in this current work to have the potential of being hepatoprotectant, antioxidant, and anti-inflammatory agents, thus reducing the risk of hepatic cirrhosis.

AMPA receptor expression in mouse testis and spermatogonial GC-1 cells: A study on its regulation by excitatory amino acids

Excitatory amino acids (EAAs) are found present in the nervous and reproductive systems of animals. Numerous studies have demonstrated a regulatory role for Glutamate (Glu), d-aspartate ( d-Asp) and N-methyl- d-aspartate (NMDA) in the control of spermatogenesis. EAAs are able to stimulate the Glutamate receptors, including the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR). Here in, we assess expression of the main AMPAR subunits, GluA1 and GluA2/3, in the mouse testis and in spermatogonial GC-1 cells. The results showed that both GluA1 and GluA2/3 were localized in mouse testis prevalently in spermatogonia. The subunit GluA2/3 was more highly expressed compared with GluA1 in both the testis and the GC-1 cells. Subsequently, GC-1 cells were incubated with medium containing l-Glu, d-Glu, d-Asp or NMDA to determine GluA1 and GluA2/3 expressions. At 30 minutes and 2 hours of incubation, EAA-treated GC-1 cells showed significantly higher expression levels of both GluA1 and GluA2/3. Furthermore, p-extracellular signal-regulated kinase (ERK), p-Akt, proliferating cell nuclear antigen (PCNA), and Aurora B expressions were assayed in l-Glu-, d-Glu-, and NMDA-treated GC-1 cells. At 30 minutes and 2 hours of incubation, treated GC-1 cells showed significantly higher expression levels of p-ERK and p-Akt. A consequent increase of PCNA and Aurora B expressions was induced by l-Glu and NMDA, but not by d-Glu. Our study demonstrates a direct effect of the EAAs on spermatogonial activity. In addition, the increased protein expression levels of GluA1 and GluA2/3 in EAA-treated GC-1 cells suggest that EAAs could activate ERK and Akt pathways through the AMPAR. Finally, the increased PCNA and Aurora B levels may imply an enhanced proliferative activity.

Replication protein A dynamically regulates monoubiquitination of proliferating cell nuclear antigen

DNA damage tolerance permits bypass of DNA lesions encountered during S-phase and may be carried out by translesion DNA synthesis (TLS). Human TLS requires selective monoubiquitination of proliferating cell nuclear antigen (PCNA) sliding clamps encircling damaged DNA. This posttranslational modification (PTM) is catalyzed by Rad6/Rad18. Recent studies revealed that replication protein A (RPA), the major ssDNA-binding protein, is involved in the regulation of PCNA monoubiquitination and interacts directly with Rad18 on chromatin and in the nucleoplasm. However, it is unclear how RPA regulates this critical PTM and what functional role(s) these interactions serve. Here, we developed an in vitro assay to quantitatively monitor PCNA monoubiquitination under in vivo scenarios. Results from extensive experiments revealed that RPA regulates Rad6/Rad18 activity in an ssDNA-dependent manner. We found that "DNA-free" RPA inhibits monoubiquitination of free PCNA by directly interacting with Rad18. This interaction is promoted under native conditions when there is an overabundance of free RPA in the nucleoplasm where Rad6/Rad18 and a significant fraction of PCNA reside. During DNA replication stress, RPA binds the ssDNA exposed downstream of stalled primer/template (P/T) junctions, releasing Rad6/Rad18. RPA restricted the resident PCNAs to the upstream duplex regions by physically blocking diffusion of PCNA along ssDNA, and this activity was required for efficient monoubiquitination of PCNA on DNA. Furthermore, upon binding ssDNA, RPA underwent a conformational change that increased its affinity for Rad18. Rad6/Rad18 complexed with ssDNA-bound RPA was active, and this interaction may selectively promote monoubiquitination of PCNA on long RPA-coated ssDNA.

The p12 subunit of human polymerase δ uses an atypical PIP box for molecular recognition of proliferating cell nuclear antigen (PCNA)

Human DNA polymerase δ is essential for DNA replication and acts in conjunction with the processivity factor proliferating cell nuclear antigen (PCNA). In addition to its catalytic subunit (p125), pol δ comprises three regulatory subunits (p50, p68, and p12). PCNA interacts with all of these subunits, but only the interaction with p68 has been structurally characterized. Here, we report solution NMR-, isothermal calorimetry-, and X-ray crystallography-based analyses of the p12-PCNA interaction, which takes part in the modulation of the rate and fidelity of DNA synthesis by pol δ. We show that p12 binds with micromolar affinity to the classical PIP-binding pocket of PCNA via a highly atypical PIP box located at the p12 N terminus. Unlike the canonical PIP box of p68, the PIP box of p12 lacks the conserved glutamine; binds through a 2-fork plug made of an isoleucine and a tyrosine residue at +3 and +8 positions, respectively; and is stabilized by an aspartate at +6 position, which creates a network of intramolecular hydrogen bonds. These findings add to growing evidence that PCNA can bind a diverse range of protein sequences that may be broadly grouped as PIP-like motifs as has been previously suggested.

Preferential digestion of PCNA-ubiquitin and p53-ubiquitin linkages by USP7 to remove polyubiquitin chains from substrates

Ubiquitin-specific protease 7 (USP7) regulates various cellular pathways through its deubiquitination activity. Despite the identification of a growing number of substrates of USP7, the molecular mechanism by which USP7 removes ubiquitin chains from polyubiquitinated substrates remains unexplored. The present study investigated the mechanism underlying the deubiquitination of Lys⁶³-linked polyubiquitinated proliferating cell nuclear antigen (PCNA). Biochemical analyses demonstrated that USP7 efficiently removes polyubiquitin chains from polyubiquitinated PCNA by preferential cleavage of the PCNA-ubiquitin linkage. This property was largely attributed to the poor activity toward Lys⁶³-linked ubiquitin chains. The preferential cleavage of substrate-ubiquitin linkages was also observed for Lys⁴⁸-linked polyubiquitinated p53 because of the inefficient cleavage of the Lys⁴⁸-linked ubiquitin chains. The present findings suggest a mechanism underlying the removal of polyubiquitin signals by USP7.

Long noncoding RNA LINC00961 inhibits cell proliferation and induces cell apoptosis in human non-small cell lung cancer

Long noncoding RNAs (LncRNAs) have been identified in multiple human cancer types, including lung cancer. An increasing number of studies have indicated that lncRNAs can function as important gene regulators. However, the biological mechanism of LINC00961 in lung cancerremains poorly understood. In our current study, we recognized lncRNA LINC00961, and we observed that it was significantly reduced in human non-small cell lung cancer (NSCLC) tissues. LINC00961 was elevated by infecting LV-LINC00961, while decreased by LV-shLINC00961 in H226 and A549 cells. Furthermore, it was shown that LINC00961 overexpression greatly inhibited lung cancer cell proliferation, whereas downregulated LINC00961 induced cell proliferation. In addition, further experiments showed that restoration of LINC00961 could dramatically increase apoptotic ratios of NSCLC H226 and A549 cells, and knockdown of LINC00961 exhibited an opposite effect. Moreover, Western blot analysis showed that upregulation of LINC00961 repressed proliferating cell nuclear antigen expression and increased Bax expression, indicating that it acts as an important pro-apoptosis gene. Conversely, inhibition of LINC00961 induced proliferating cell nuclear antigen expression and restrained Bax protein levels. Taking these together, LINC00961 might play a tumor suppressive role in NSCLC progression, and it could serve as a novel prognostic biomarker in NSCLC diagnosis and treatment.

[Time-effect relationship and molecular mechanism of electroacupuncture for repair of gastric mucosal lesion]

OBJECTIVE

To dynamically observe the effects of electroacupuncture (EA) on repair of gastric mucosal lesion in rats with gastric ulcer, and to explore the time-effect relationship and molecular mechanism of EA for gastric ulcer.

METHODS

A total of 72 SD rats were randomly assigned to a normal group, a model group, a acupoint group and a sham acupoint group, and each group were further divided into a 1-day subgroup, a 4-day subgroup and a 7-day subgroup, 6 rats in each subgroup. The rat model of gastric ulcer was established by using intragastric administration of ethyl alcohol. The rats in the acupoint group were treated with EA at"Zusanli"(ST 36) and"Liangmen"(ST 21); the rats in the sham acupoint group were treated with EA at points 5 mm next to"Zusanli"(ST 36) and"Liangmen"(ST 21); the EA was given 30 min per treatment, once a day. The rats in the normal group and model group were treated with immobilization for 30 min per day, and no EA was given. PR-PCR method was applied to test the expression of proliferating cell nuclear antigen (PCNA) and substance P (SP); Western blot method was applied to test the expression of neurotensin (NT).

RESULTS

After 1-day treatment, the ulcer index in the model group was higher than that in the normal group (P<0.01), and the expression of PCNA, SP and NT was decreased (P<0.01, P<0.05); compared with the model group and sham acupoint group, the ulcer index was decreased in the acupoint group (both P<0.05), and the expression of PCNA and SP was up-regulated (all P<0.05) while that of NT was up-regulated (both P<0.01). After 4-day treatment, the ulcer index in the model group was reduced but still higher than that in the normal group (P<0.05), and the expression of PCNA, SP and NT was up-regulated and higher than that in the normal group (all P<0.01); the ulcer index in the acupoint group was similar to that in the normal group (P>0.05), and the expression of PCNA and SP was lower than that in the model group (P<0.01, P<0.05), and the expression of NT was not significantly different from that in the model group (P>0.05). After 7-day treatment, the differences of indexes above were not significant among the four groups (all P>0.05).

CONCLUSION

EA at acupoints of stomach meridian has two-way regulation on PCNA and SP and improve the expression of NT in different pathological state of gastric ulcer, which could further improve the repair of gastric ulcer.

Histopathological changes in the choroid plexus after traumatic brain injury in the rats: a histologic and immunohistochemical study

BACKGROUND

Traumatic brain injury (TBI) is in part associated with the disruption of the blood-brain barrier. In this study, we analysed the histopathological changes in E-cadherin and vascular endothelial growth factor (VEGF) expression after TBI in rats.

MATERIALS AND METHODS

The rats were divided into two groups as the control and the trauma groups. Sprague-Dawley rats were subjected to TBI with a weight-drop device using 300 g/1 m weight-height impact. After 5 days of TBI, blood samples were taken under ketamine hydroxide anaesthesia and biochemical analyses were performed. The control and trauma groups were compared in terms of biochemical values.

RESULTS

There was no change in glutathione (GSH) levels and blood-brain barier permeability. However, malondialdehyde (MDA) and myeloperoxidase (MPO) activity levels increased in the trauma group. In the histopathological examination, choroid plexus in the lateral ventricle, near the pia mater membrane, was removed. In the traumatic group, some of epithelial cells were hyperplasic. Some of them were peeled off the apical surface and had local degeneration.

CONCLUSIONS

In addition, we observed congestion in capillary vessels and mononuclear cell infiltration around the vessels. After TBI, the increase in VEGF levels, vascular permeability, and interaction with VEGF receptors in endothelial cells lead to oedema of the vessel wall. On the other hand, E-cadherin expression decreased in the tight-junction structures between epithelial cells and basal membrane, resulting in an increase in cerebrospinal fluid in the intervillous area.

[Effects of acupuncture at opposite acupoints on expression of hepatocyte growth factor in rats with skeletal muscle contusion]

OBJECTIVE

To observe the effects of acupuncture at opposite acupoints on expression of hepatocyte growth factor (HGF) in rats with skeletal muscle contusion, and to explore the mechanism of acupuncture at opposite acupoints on skeletal muscle contusion.

METHODS

Fifty-four Sprague Dawley (SD) rats were randomly divided into a blank group (6 rats), a model group (24 rats) and an opposing needling group (24 rats). The model group and opposing needling group were further divided into 1-day subgroup, 3-day subgroup, 5-day subgroup and 7-day subgroup, 6 rats in each one. No intervention was given in the blank group, while the model of skeletal muscle contusion was established in the model group and opposing needling group by self-made contusion device. 24 hours after contusion, electroacupuncture (EA) was applied at "Zusanli" (ST 36) and the corresponding points of ashi points at health side for 15 min, once a day. The subgroups of opposing needling group were treated for 1 day, 3 days, 5 days and 7 days, respectively. No treatment was given in the model group. Samples were collected in the subgroups 1 day, 3 days, 5 days and 7 days after treatment. The morphological change of injured gastrocnemius muscle was observed by using microscope after HE staining. The positive cell rate of proliferating cell nuclear antigen (PCNA) was detected by immunohistochemistry. The expression levels of HGF protein and PCNA protein were observed by Western blot.

RESULTS

① The results of HE staining showed that, 1 day after contusion, the inflammatory cells of gastrocnemius muscle in the opposing needling group were less than those in the model group; 3 days and 5 days after contusion, myoblasts and myotubes in the opposing needling group were more than those in the model group; 7 days after contusion, the neonatal muscle cells in the opposing needling group were more than those in the model group. ② The results of immunohistochemistry showed that, 1 day, 3 days and 5 days after contusion, the positive cell rate of PCNA in the opposing needling group was significantly higher than that in the model group (all P<0.001); 7 days after contusion, the positive cell rate of PCNA in the opposing needling group was significantly less than that in the model group (P<0.001). ③ The results of Western blot showed that, 1 day, 3 days and 5 days after contusion, the expression of HGF protein and PCNA protein in the opposing needling group was significantly higher than that in the model group (all P<0.05); 7 days after contusion, the expression of HGF protein and PCNA protein in the opposing needling group was significantly lower than that in the model group (all P<0.05).

CONCLUSION

Acupuncture at opposite acupoints could regulate the expression of HGF and promote the activation, proliferation, migration and differentiation of muscle satellite cells in rats with skeletal muscle contusion, which could speed up the process of skeletal muscle injury repair.

miR-363-3p inhibits tumor growth by targeting PCNA in lung adenocarcinoma

Increasing evidence suggests that microRNAs play key roles in lung cancer. Our previous study demonstrated that microRNA 363-3p (miR-363-3p) is downregulated in lung cancer tissues. In this study, we demonstrated that overexpression of miR-363-3p inhibits the proliferation and colony formation of A549 and H441 cells, while silencing of miR-363-3p has the converse effects. The anti-oncogenic function of miR-363-3p was verified in a mouse tumor xenograft model. Furthermore, cell cycle analysis showed miR-363-3p can induce S phase arrest by downregulating Cyclin-D1 and upregulating Cyclin-dependent kinase-2 in lung adenocarcinoma cells. Additionally, miR-363-3p enhances cell apoptosis, whereas miR-363-3p inhibitor prevents apoptosis and leads to downregulation of Bax and Bak expression. The anti-proliferative function of miR-363-3p toward lung cancer cells may be explained by its ability to inhibit the activation of the mTOR and ERK signaling pathways. Using target prediction software and luciferase reporter assays, we identified PCNA as a specific target of miR-363-3p. miR-363-3p can decreased the accumulation of endogenous PCNA in lung adenocarcinoma cells. Moreover, exogenous expression of PCNA relieve the inhibition of miR-363-3p on cell proliferation, colony formation and mTOR and ERK signaling pathways. Taken together, our data indicate that miR-363-3p suppresses tumor growth by targeting PCNA in lung adenocarcinoma.

Nuclear insulin-like growth factor 1 receptor phosphorylates proliferating cell nuclear antigen and rescues stalled replication forks after DNA damage

We have previously shown that the insulin-like growth factor 1 receptor (IGF-1R) translocates to the cell nucleus, where it binds to enhancer-like regions and increases gene transcription. Further studies have demonstrated that nuclear IGF-1R (nIGF-1R) physically and functionally interacts with some nuclear proteins, i.e. the lymphoid enhancer-binding factor 1 (Lef1), histone H3, and Brahma-related gene-1 proteins. In this study, we identified the proliferating cell nuclear antigen (PCNA) as a nIGF-1R-binding partner. PCNA is a pivotal component of the replication fork machinery and a main regulator of the DNA damage tolerance (DDT) pathway. We found that IGF-1R interacts with and phosphorylates PCNA in human embryonic stem cells and other cell lines. In vitro MS analysis of PCNA co-incubated with the IGF-1R kinase indicated tyrosine residues 60, 133, and 250 in PCNA as IGF-1R targets, and PCNA phosphorylation was followed by mono- and polyubiquitination. Co-immunoprecipitation experiments suggested that these ubiquitination events may be mediated by DDT-dependent E2/E3 ligases (e.g. RAD18 and SHPRH/HLTF). Absence of IGF-1R or mutation of Tyr-60, Tyr-133, or Tyr-250 in PCNA abrogated its ubiquitination. Unlike in cells expressing IGF-1R, externally induced DNA damage in IGF-1R-negative cells caused G₁ cell cycle arrest and S phase fork stalling. Taken together, our results suggest a role of IGF-1R in DDT.

Proteomic Analysis of Human Angiogenin Interactions Reveals Cytoplasmic PCNA as a Putative Binding Partner

Human Angiogenin (hAng) is a member of the ribonuclease A superfamily and a potent inducer of neovascularization. Protein interactions of hAng in the nucleus and cytoplasm of the human umbilical vein cell line EA.hy926 have been investigated by mass spectroscopy. Data are available via ProteomeXchange with identifiers PXD006583 and PXD006584. The first gel-free analysis of hAng immunoprecipitates revealed many statistically significant potential hAng-interacting proteins involved in crucial biological pathways. Surprisingly, proliferating cell nuclear antigen (PCNA), was found to be immunoprecipitated with hAng only in the cytoplasm. The hAng-PCNA interaction and colocalization in the specific cellular compartment was validated with immunoprecipitation, immunoblotting, and immunocytochemistry. The results revealed that PCNA is predominantly localized in the cytoplasm, while hAng is distributed both in the nucleus and in the cytoplasm. hAng and PCNA colocalize in the cytoplasm, suggesting that they may interact in this compartment.

Linchpin DNA-binding residues serve as go/no-go controls in the replication factor C-catalyzed clamp-loading mechanism

DNA polymerases depend on circular sliding clamps for processive replication. Clamps must be loaded onto primer-template DNA (ptDNA) by clamp loaders that open and close clamps around ptDNA in an ATP-fueled reaction. All clamp loaders share a core structure in which five subunits form a spiral chamber that binds the clamp at its base in a twisted open form and encloses ptDNA within, while binding and hydrolyzing ATP to topologically link the clamp and ptDNA. To understand how clamp loaders perform this complex task, here we focused on conserved arginines that might play a central coordinating role in the mechanism because they can alternately contact ptDNA or Walker B glutamate in the ATPase site and lie close to the clamp loader-clamp-binding interface. We mutated Arg-84, Arg-88, and Arg-101 in the ATPase-active B, C, and D subunits of Saccharomyces cerevisiae replication factor C (RFC) clamp loader, respectively, and assessed the impact on multiple transient events in the reaction: proliferating cell nuclear antigen (PCNA) clamp binding/opening/closure/release, ptDNA binding/release, and ATP hydrolysis/product release. The results show that these arginines relay critical information between the PCNA-binding, DNA-binding, and ATPase sites at all steps of the reaction, particularly at a checkpoint before RFC commits to ATP hydrolysis. Moreover, their actions are subunit-specific with RFC-C Arg-88 serving as an accelerator that enables rapid ATP hydrolysis upon contact with ptDNA and RFC-D Arg-101 serving as a brake that confers specificity for ptDNA as the correct substrate for loading PCNA.

The herpes simplex virus 1 UL36USP deubiquitinase suppresses DNA repair in host cells via deubiquitination of proliferating cell nuclear antigen

Herpes simplex virus 1 (HSV-1) infection manipulates distinct host DNA-damage responses to facilitate virus proliferation, but the molecular mechanisms remain to be elucidated. One possible HSV-1 target might be DNA damage-tolerance mechanisms, such as the translesion synthesis (TLS) pathway. In TLS, proliferating cell nuclear antigen (PCNA) is monoubiquitinated in response to DNA damage-caused replication fork stalling. Ubiquitinated PCNA then facilitates the error-prone DNA polymerase η (polη)-mediated TLS, allowing the fork to bypass damaged sites. Because of the involvement of PCNA ubiquitination in DNA-damage repair, we hypothesized that the function of PCNA might be altered by HSV-1. Here we show that PCNA is a substrate of the HSV-1 deubiquitinase UL36USP, which has previously been shown to be involved mainly in virus uptake and maturation. In HSV-1-infected cells, viral infection-associated UL36USP consistently reduced PCNA ubiquitination. The deubiquitination of PCNA inhibited the formation of polη foci and also increased cell sensitivity to DNA-damage agents. Moreover, the catalytically inactive mutant UL36C40A failed to deubiquitinate PCNA. Of note, the levels of virus marker genes increased strikingly in cells infected with wild-type HSV-1, but only moderately in UL36C40A mutant virus-infected cells, indicating that the UL36USP deubiquitinating activity supports HSV-1 virus replication during infection. These findings suggest a role of UL36USP in the DNA damage-response pathway.

Extracellular-signal regulated kinase 8 of Trypanosoma brucei uniquely phosphorylates its proliferating cell nuclear antigen homolog and reveals exploitable properties

The Trypanosoma brucei subspecies T. brucei gambiense and T. brucei rhodesiense are vector-borne pathogens that cause sleeping sickness also known as Human African Trypanosomiasis (HAT), which is fatal if left untreated. The drugs that treat HAT are ineffective and cause toxic side effects. One strategy for identifying safer and more effective HAT drugs is to therapeutically exploit essential gene targets in T. brucei. Genes that make up a basic mitogen-activated protein kinase (MAPK) network are present in T. brucei. Tb927.10.5140 encodes an essential MAPK that is homologous to the human extracellular-signal regulated kinase 8 (HsERK8) which forms a tight complex with the replication factor proliferating cell nuclear antigen (PCNA) to stabilize intracellular PCNA levels. Here we demonstrate that (TbPCNA) is uniquely phos-phorylated on serine (S) and threonine (T) residues in T. brucei and that TbERK8 phosphorylates TbPCNA at each of these residues. The ability of an ERK8 homolog to phosphorylate a PCNA homolog is a novel biochemical property that is first demonstrated here in T. brucei and may be unique to this pathogen. We demonstrate that the potent HsERK8 inhibitor Ro318220, has an IC₅₀ for TbERK8 that is several hundred times higher than its reported IC₅₀ for HsERK8. This indicated that the active sites of TbERK8 and HsERK8 can be selectively inhibited, which provides a rational basis for discovering inhibitors that specifically target this essential parasite MAPK to kill the parasite.

MMSET is dynamically regulated during cell-cycle progression and promotes normal DNA replication

The timely and precise duplication of cellular DNA is essential for maintaining genome integrity and is thus tightly-regulated. During mitosis and G1, the Origin Recognition Complex (ORC) binds to future replication origins, coordinating with multiple factors to load the minichromosome maintenance (MCM) complex onto future replication origins as part of the pre-replication complex (pre-RC). The pre-RC machinery, in turn, remains inactive until the subsequent S phase when it is required for replication fork formation, thereby initiating DNA replication. Multiple myeloma SET domain-containing protein (MMSET, a.k.a. WHSC1, NSD2) is a histone methyltransferase that is frequently overexpressed in aggressive cancers and is essential for normal human development. Several studies have suggested a role for MMSET in cell-cycle regulation; however, whether MMSET is itself regulated during cell-cycle progression has not been examined. In this study, we report that MMSET is degraded during S phase in a cullin-ring ligase 4-Cdt2 (CRL4(Cdt2)) and proteasome-dependent manner. Notably, we also report defects in DNA replication and a decreased association of pre-RC factors with chromatin in MMSET-depleted cells. Taken together, our results suggest a dynamic regulation of MMSET levels throughout the cell cycle, and further characterize the role of MMSET in DNA replication and cell-cycle progression.

Human DNA Ligase I Interacts with and Is Targeted for Degradation by the DCAF7 Specificity Factor of the Cul4-DDB1 Ubiquitin Ligase Complex

The synthesis, processing, and joining of Okazaki fragments during DNA replication is complex, requiring the sequential action of a large number of proteins. Proliferating cell nuclear antigen, a DNA sliding clamp, interacts with and coordinates the activity of several DNA replication proteins, including the enzymes flap endonuclease 1 (FEN-1) and DNA ligase I that complete the processing and joining of Okazaki fragments, respectively. Although it is evident that maintaining the appropriate relative stoichiometry of FEN-1 and DNA ligase I, which compete for binding to proliferating cell nuclear antigen, is critical to prevent genomic instability, little is known about how the steady state levels of DNA replication proteins are regulated, in particular the proteolytic mechanisms involved in their turnover. Because DNA ligase I has been reported to be ubiquitylated, we used a proteomic approach to map ubiquitylation sites and screen for DNA ligase I-associated E3 ubiquitin ligases. We identified three ubiquitylated lysine residues and showed that DNA ligase I interacts with and is targeted for ubiquitylation by DCAF7, a specificity factor for the Cul4-DDB1 complex. Notably, knockdown of DCAF7 reduced the degradation of DNA ligase I in response to inhibition of proliferation and replacement of ubiquitylated lysine residues reduced the in vitro ubiquitylation of DNA ligase I by Cul4-DDB1 and DCAF7. In contrast, a different E3 ubiquitin ligase regulates FEN-1 turnover. Thus, although the expression of many of the genes encoding DNA replication proteins is coordinately regulated, our studies reveal that different mechanisms are involved in the turnover of these proteins.

Effects of 1,25(OH)2D3 on proliferation and apoptosis of human glomerular mesangial cells

OBJECTIVE

To investigate the effect of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on cell proliferation and apoptosis of human glomerular mesangial cells.

METHODS

Human glomerular mesangial cells were cultured for 48 h and randomly divided into four groups, normal control group (N group), proliferation group (EGF group ), vitamin D3 intervention group (VD3 group), proliferation intervention group (EGF+VD3 group ). Flow cytometry was used to detect the cell cycle and apoptosis rate, and Western blot was used to detect the PCNA and Caspases-3 expression. The effect of 1,25(OH)2D3 on human mesangial cell proliferation was detected by CCK-8.

RESULTS

Compared with the control group, G1 phase cells in EGF group were significantly reduced, S, G2/M phase cells were increased, and the higher PI and PCNA expression levels were increased; G1 phase cells in VD3 group were increased, S, G2/M phase cells were decreased, and the lower PI and PCNA expression levels were reduced. Compared with EGF group, G1 phase cells in EGF+VD3 group were increased, S, G2/M phase cells were decreased, and the lower PI and PCNA expression levels were significantly reduced. Compared with normal control group, the apoptosis rate in EGF group was significantly lower, and the Caspase-3 expression level was reduced; the apoptosis rate in VD3 group was significantly higher, and Caspase-3 expression was significantly increased. Compared with EGF group, the apoptotic rate of mesangial cells in EGF+VD3 group was significantly increased, and the Caspase-3 expression level was increased, with significant difference.

CONCLUSION

1,25(OH)2D3 inhibited the proliferation of mesangial cells and induced their apoptosis by blocking the cell cycle, inhibiting expression of PCNA, and upregulating Caspase-3 expression.

Proficient Replication of the Yeast Genome by a Viral DNA Polymerase

DNA replication in eukaryotic cells requires minimally three B-family DNA polymerases: Pol α, Pol δ, and Pol ϵ. Pol δ replicates and matures Okazaki fragments on the lagging strand of the replication fork. Saccharomyces cerevisiae Pol δ is a three-subunit enzyme (Pol3-Pol31-Pol32). A small C-terminal domain of the catalytic subunit Pol3 carries both iron-sulfur cluster and zinc-binding motifs, which mediate interactions with Pol31, and processive replication with the replication clamp proliferating cell nuclear antigen (PCNA), respectively. We show that the entire N-terminal domain of Pol3, containing polymerase and proofreading activities, could be effectively replaced by those from bacteriophage RB69, and could carry out chromosomal DNA replication in yeast with remarkable high fidelity, provided that adaptive mutations in the replication clamp PCNA were introduced. This result is consistent with the model that all essential interactions for DNA replication in yeast are mediated through the small C-terminal domain of Pol3. The chimeric polymerase carries out processive replication with PCNA in vitro; however, in yeast, it requires an increased involvement of the mutagenic translesion DNA polymerase ζ during DNA replication.

Deletions of Retinoblastoma 1 (Rb1) and Its Repressing Target S Phase Kinase-associated protein 2 (Skp2) Are Synthetic Lethal in Mouse Embryogenesis

Tumor suppressor pRb represses Skp2, a substrate-recruiting subunit of the SCF(Skp2) ubiquitin ligase. Rb1(+/-) mice incur "two-hit" pituitary tumorigenesis; Skp2(-/-);Rb1(+/-) mice do not. Rb1(-/-) embryos die on embryonic day (E) 14.5-15.5. Here, we report that Skp2(-/-);Rb1(-/-) embryos died on E11.5, establishing an organismal level synthetic lethal relationship between Rb1 and Skp2 On E10.5, Rb1(-/-) placentas showed similarly active proliferation and similarly inactive apoptosis as WT placenta, whereas Rb1(-/-) embryos showed ectopic proliferation without increased apoptosis in the brain. Combining Skp2(-/-) did not reduce proliferation or increase apoptosis in the placentas but induced extensive apoptosis in the brain. We conditionally deleted Rb1 in neuronal lineage with Nes-Cre and reproduced the brain apoptosis in E13.5 Nes-Cre;Rb1(lox/lox);Skp2(-/-) embryos, demonstrating their synthetic lethal relationship at a cell autonomous level. Nes-Cre-mediated Rb1 deletion increased expression of proliferative E2F target genes in the brains of Skp2(+/+) embryos; the increases rose higher with activation of expression of apoptotic E2F target genes in Skp2(-/-) embryos. The brain apoptosis was independent of p53 but coincident with proliferation. The highly activated expression of proliferative and apoptotic E2F target genes subsided with gradually reduced roles of Skp2 in preventing p27 protein accumulation in the brain in late gestation, allowing the embryos to reach full term with normally sized brains. These findings establish that Rb1 and Skp2 deletions are synthetic lethal and suggest how this lethal relationship might be circumvented, which could help design better therapies for pRb-deficient cancer.

DNA Mismatch Repair Interacts with CAF-1- and ASF1A-H3-H4-dependent Histone (H3-H4)2 Tetramer Deposition

DNA mismatch repair (MMR) is required for the maintenance of genome stability and protection of humans from several types of cancer. Human MMR occurs in the chromatin environment, but little is known about the interactions between MMR and the chromatin environment. Previous research has suggested that MMR coincides with replication-coupled assembly of the newly synthesized DNA into nucleosomes. The first step in replication-coupled nucleosome assembly is CAF-1-dependent histone (H3-H4)2 tetramer deposition, a process that involves ASF1A-H3-H4 complex. In this work we used reconstituted human systems to investigate interactions between MMR and CAF-1- and ASF1A-H3-H4-dependent histone (H3-H4)2 tetramer deposition. We have found that MutSα inhibits CAF-1- and ASF1A-H3-H4-dependent packaging of a DNA mismatch into a tetrasome. This finding supports the idea that MMR occurs before the DNA mismatch is packaged into the tetrasome. Our experiments have also revealed that CAF-1- and ASF1A-H3-H4-dependent deposition of the histone (H3-H4)2 tetramers does not interfere with MMR reactions. In addition, we have established that unnecessary degradation of the discontinuous strand that takes place in both DNA polymerase δ (Pol δ)- and DNA polymerase ϵ (Pol ϵ)-dependent MMR reactions is suppressed by CAF-1- and ASF1A-H3-H4-dependent deposition of the histone (H3-H4)2 tetramers. These data suggest that CAF-1- and ASF1A-H3-H4-dependent deposition of the histone (H3-H4)2 tetramers is compatible with MMR and protects the discontinuous daughter strand from unnecessary degradation by MMR machinery.

Validating the disruption of proliferating cell nuclear antigen interactions in the development of targeted cancer therapeutics

Human DNA replication and repair is a highly coordinated process involving the specifically timed actions of numerous proteins and enzymes. Many of these proteins require interaction with proliferating cell nuclear antigen (PCNA) for activation within the process. The interdomain connector loop (IDCL) of PCNA provides a docking site for many of those proteins, suggesting that this region is critically important in the regulation of cellular function. Previous work in this laboratory has demonstrated that a peptide mimicking a specific region of the IDCL (caPeptide) has the ability to disrupt key protein-protein interactions between PCNA and its binding partners, thereby inhibiting DNA replication within the cells. In this study, we confirm the ability of the caPeptide to disrupt DNA replication function using both intact cell and in vitro DNA replication assays. Further, we were able to demonstrate that treatment with caPeptide results in a decrease of polymerase δ activity that correlates with the observed decrease in DNA replication. We have also successfully developed a surface plasmon resonance (SPR) assay to validate the disruption of the PCNA-pol δ interaction with caPeptide.

Pro-recombination Role of Srs2 Protein Requires SUMO (Small Ubiquitin-like Modifier) but Is Independent of PCNA (Proliferating Cell Nuclear Antigen) Interaction

Srs2 plays many roles in DNA repair, the proper regulation and coordination of which is essential. Post-translational modification by small ubiquitin-like modifier (SUMO) is one such possible mechanism. Here, we investigate the role of SUMO in Srs2 regulation and show that the SUMO-interacting motif (SIM) of Srs2 is important for the interaction with several recombination factors. Lack of SIM, but not proliferating cell nuclear antigen (PCNA)-interacting motif (PIM), leads to increased cell death under circumstances requiring homologous recombination for DNA repair. Simultaneous mutation of SIM in asrs2ΔPIMstrain leads to a decrease in recombination, indicating a pro-recombination role of SUMO. Thus SIM has an ambivalent function in Srs2 regulation; it not only mediates interaction with SUMO-PCNA to promote the anti-recombination function but it also plays a PCNA-independent pro-recombination role, probably by stimulating the formation of recombination complexes. The fact that deletion of PIM suppresses the phenotypes of Srs2 lacking SIM suggests that proper balance between the anti-recombination PCNA-bound and pro-recombination pools of Srs2 is crucial. Notably, sumoylation of Srs2 itself specifically stimulates recombination at the rDNA locus.

Clinical significance of bile reflux into the pancreatic duct without pancreaticobiliary maljunction assessed by intraoperative cholangiography

INTRODUCTION

Bile reflux into the pancreatic duct (BRPD) is sometimes demonstrated during intraoperative cholangiography (IOC) even in patients without pancreaticobiliary maljunction. However, the clinical significance of this finding in laparoscopic and open cholecystectomy is unclear.

METHODS

Among 484 patients who underwent cholecystectomy (372 laparoscopic, 112 open), patients whose pancreatic duct was depicted in IOC were selected. The value of pancreatic amylase (p-amylase) of the gallbladder bile, histological changes, and the immunohistochemical expression of proliferating cell nuclear antigen (PCNA) in the gallbladder mucosa were analyzed in patients with BRPD. The data were then compared to those in patients without BRPD whose gallbladder bile p-amylase was measured (control group, n = 20).

RESULTS

The success rate of IOC was 93.6%. The rate of BRPD in laparoscopic and open cholecystectomy was 5.2% and 5.7%, respectively. The value of gallbladder bile p-amylase in patients with BRPD was significantly higher than in the control group (790.5 vs 14.0 IU/L, P = 0.034). The value of the PCNA labeling index in patients with BRPD was significantly higher than that of the control group (15.4% vs 4.1%, P = 0.0026). Among the 24 patients with BRPD, pathological changes in the gallbladder mucosa were detected in five (two hyperplasia, three metaplasia), but there was no correlation between the presence of pathological change and PCNA labeling index or gallbladder bile p-amylase.

CONCLUSIONS

IOC could detect BRPD both in laparoscopic and open cholecystectomy at a similar rate. Patients with BRPD had high levels of gallbladder bile p-amylase and PCNA labeling index, findings similar to those in patients with pancreaticobiliary maljunction.

Activation of Saccharomyces cerevisiae Mlh1-Pms1 Endonuclease in a Reconstituted Mismatch Repair System

Previous studies reported the reconstitution of an Mlh1-Pms1-independent 5′ nick-directed mismatch repair (MMR) reaction using Saccharomyces cerevisiae proteins. Here we describe the reconstitution of a mispair-dependent Mlh1-Pms1 endonuclease activation reaction requiring Msh2-Msh6 (or Msh2-Msh3), proliferating cell nuclear antigen (PCNA), and replication factor C (RFC) and a reconstituted Mlh1-Pms1-dependent 3′ nick-directed MMR reaction requiring Msh2-Msh6 (or Msh2-Msh3), exonuclease 1 (Exo1), replication protein A (RPA), RFC, PCNA, and DNA polymerase δ. Both reactions required Mg²⁺ and Mn²⁺ for optimal activity. The MMR reaction also required two reaction stages in which the first stage required incubation of Mlh1-Pms1 with substrate DNA, with or without Msh2-Msh6 (or Msh2-Msh3), PCNA, and RFC but did not require nicking of the substrate, followed by a second stage in which other proteins were added. Analysis of different mutant proteins demonstrated that both reactions required a functional Mlh1-Pms1 endonuclease active site, as well as mispair recognition and Mlh1-Pms1 recruitment by Msh2-Msh6 but not sliding clamp formation. Mutant Mlh1-Pms1 and PCNA proteins that were defective for Exo1-independent but not Exo1-dependent MMR in vivo were partially defective in the Mlh1-Pms1 endonuclease and MMR reactions, suggesting that both reactions reflect the activation of Mlh1-Pms1 seen in Exo1-independent MMR in vivo. The availability of this reconstituted MMR reaction should now make it possible to better study both Exo1-independent and Exo1-dependent MMR.

14-3-3 proteins restrain the Exo1 nuclease to prevent overresection

The DNA end resection process dictates the cellular response to DNA double strand break damage and is essential for genome maintenance. Although insufficient DNA resection hinders homology-directed repair and ATR (ataxia telangiectasia and Rad3 related)-dependent checkpoint activation, overresection produces excessive single-stranded DNA that could lead to genomic instability. However, the mechanisms controlling DNA end resection are poorly understood. Here we show that the major resection nuclease Exo1 is regulated both positively and negatively by protein-protein interactions to ensure a proper level of DNA resection. We have shown previously that the sliding DNA clamp proliferating cell nuclear antigen (PCNA) associates with the C-terminal domain of Exo1 and promotes Exo1 damage association and DNA resection. In this report, we show that 14-3-3 proteins interact with a central region of Exo1 and negatively regulate Exo1 damage recruitment and subsequent resection. 14-3-3s limit Exo1 damage association, at least in part, by suppressing its association with PCNA. Disruption of the Exo1 interaction with 14-3-3 proteins results in elevated sensitivity of cells to DNA damage. Unlike Exo1, the Dna2 resection pathway is apparently not regulated by PCNA and 14-3-3s. Our results provide critical insights into the mechanism and regulation of the DNA end resection process and may have implications for cancer treatment.

Arsenic Inhibits DNA Mismatch Repair by Promoting EGFR Expression and PCNA Phosphorylation

Both genotoxic and non-genotoxic chemicals can act as carcinogens. However, while genotoxic compounds lead directly to mutations that promote unregulated cell growth, the mechanism by which non-genotoxic carcinogens lead to cellular transformation is poorly understood. Using a model non-genotoxic carcinogen, arsenic, we show here that exposure to arsenic inhibits mismatch repair (MMR) in human cells, possibly through its ability to stimulate epidermal growth factor receptor (EGFR)-dependent tyrosine phosphorylation of proliferating cellular nuclear antigen (PCNA). HeLa cells exposed to exogenous arsenic demonstrate a dose- and time-dependent increase in the levels of EGFR and tyrosine 211-phosphorylated PCNA. Cell extracts derived from arsenic-treated HeLa cells are defective in MMR, and unphosphorylated recombinant PCNA restores normal MMR activity to these extracts. These results suggest a model in which arsenic induces expression of EGFR, which in turn phosphorylates PCNA, and phosphorylated PCNA then inhibits MMR, leading to increased susceptibility to carcinogenesis. This study suggests a putative novel mechanism of action for arsenic and other non-genotoxic carcinogens.

Cytokine-induced killer cells combined with dendritic cells inhibited liver cancer cells

OBJECTIVES

To investigate the prognosis of advanced liver cancer patients treated with CIK-DCs and the mechanism of apoptosis of HEPG 2 cells.

METHODS

67 patients were enrolled in the study. Peripheral blood mononuclear cells (PBMCs) were separated, of which adherent PBMCs used granulocyte 2 macrophage colony2 stimulating factor (GM2CSF), tumor necrosis factor 2α (TNF2α), and interleukin 24 (IL24) to induce DCs, which were sensitized with antigen of autologous or exogenous cancer cells to obtain Ag-DCs; suspended PBMCs used interferon 2γ (IFN2γ), IL-2, and CD 3 monoclonal antibody (CD3mAb) respectively, to induce CIK cells. DCs and CIK cells were cultured together. Flow cytometry was used to detect the phenotypes of DCs and CIK cells, and the blood retransfused into patients. Western blot and flow cytometer were used to analyze the growth cycle of HepG 2 cells and the expression of BAX and PCNA.

RESULTS

No patients underwent complete remission, 5 obtained partial remission and 29 had stable disease. Of the 31 patients whose lesions could not be evaluated, 17 received effective treatment, showing that the immune response was enhanced. In vitro laboratory experiments revealed that DC-CIK cells markedly affected the growth cycle of HepG 2 cells. Analysis showed that DC-CIK cells enhanced the gene expression of BAX and inhibited the activity of PCNA.

CONCLUSIONS

Co-cultured DCs and CIK cells inhibit the proliferation and migration of liver cancer cells by down-regulating PCNA and up-regulating BAX. This approach may be an effective method to treat advanced liver cancer.