Dicer promotes tumorigenesis by translocating to nucleus to promote SFRP1 promoter methylation in cholangiocarcinoma cells

Unveiling the role of HP1α-HDAC1-STAT1 axis as a therapeutic target for HP1α-positive intrahepatic cholangiocarcinoma

BACKGROUND

Intrahepatic cholangiocarcinoma (ICCA) is a heterogeneous group of malignant tumors characterized by high recurrence rate and poor prognosis. Heterochromatin Protein 1α (HP1α) is one of the most important nonhistone chromosomal proteins involved in transcriptional silencing via heterochromatin formation and structural maintenance. The effect of HP1α on the progression of ICCA remained unclear.

METHODS

The effect on the proliferation of ICCA was detected by experiments in two cell lines and two ICCA mouse models. The interaction between HP1α and Histone Deacetylase 1 (HDAC1) was determined using Electrospray Ionization Mass Spectrometry (ESI-MS) and the binding mechanism was studied using immunoprecipitation assays (co-IP). The target gene was screened out by RNA sequencing (RNA-seq). The occupation of DNA binding proteins and histone modifications were predicted by bioinformatic methods and evaluated by Cleavage Under Targets and Tagmentation (CUT & Tag) and Chromatin immunoprecipitation (ChIP).

RESULTS

HP1α was upregulated in intrahepatic cholangiocarcinoma (ICCA) tissues and regulated the proliferation of ICCA cells by inhibiting the interferon pathway in a Signal Transducer and Activator of Transcription 1 (STAT1)-dependent manner. Mechanistically, STAT1 is transcriptionally regulated by the HP1α-HDAC1 complex directly and epigenetically via promoter binding and changes in different histone modifications, as validated by high-throughput sequencing. Broad-spectrum HDAC inhibitor (HDACi) activates the interferon pathway and inhibits the proliferation of ICCA cells by downregulating HP1α and targeting the heterodimer. Broad-spectrum HDACi plus interferon preparation regimen was found to improve the antiproliferative effects and delay ICCA development in vivo and in vitro, which took advantage of basal activation as well as direct activation of the interferon pathway. HP1α participates in mediating the cellular resistance to both agents.

CONCLUSIONS

HP1α-HDAC1 complex influences interferon pathway activation by directly and epigenetically regulating STAT1 in transcriptional level. The broad-spectrum HDACi plus interferon preparation regimen inhibits ICCA development, providing feasible strategies for ICCA treatment. Targeting the HP1α-HDAC1-STAT1 axis is a possible strategy for treating ICCA, especially HP1α-positive cases.

Targeting polycomb repressor complex 2-mediated bivalent promoter epigenetic silencing of secreted frizzled-related protein 1 inhibits cholangiocarcinoma progression

BACKGROUND

Cholangiocarcinoma (CCA) refers to a collection of malignancies that are associated with a dismal prognosis. Currently, surgical resection is the only way to cure patients with CCA. Available systemic therapy is limited to gemcitabine plus cisplatin; however, this treatment is palliative in nature. Therefore, there is still a need to explore new effective therapeutic targets to intervene against CCA.

METHODS

We analyzed the expression of EZH2 and the prognosis of patients in CCA. The proliferation, migration and invasion of CCA cells after gene knockdown and overexpression were examined and validated by a xenograft model and a primary CCA mouse model with corresponding gene intervention. Targeting DNA methylation, and RNA-sequencing-based transcriptomic analysis in EZH2 and SUZ12 knockout CCA cells was performed. Bisulfite sequencing polymerase chain reaction (PCR), chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) and reverse-ChIP assays were performed for research purposes.

RESULTS

Increased expression of EZH2 in CCA exhibited a significantly poorer prognosis. DNA hypomethylation of the promoter and increased mRNA levels of secreted frizzled-related protein 1 (SFRP1) were observed in CCA cells following the inhibition of polycomb repressor complex 2 (PRC2), which was achieved through a knockout of EZH2, SUZ12 and EED, respectively, or treatment with GSK126 and GSK343. Targeting the SFRP1 promoter DNA hypermethylation with dCas9-DNMT3a decreased the mRNA level of SFRP1. The expression of SFRP1 is regulated by both H3K27me3 and DNA methylation and H3K27me3 plays a crucial role in promoting SFRP1 promotor DNA methylation. GSK343 is a small molecule inhibitor that targets the catalytic activity of EZH2. It effectively inhibits the progression and development of subcutaneous xenografts and primary CCA mouse models.

CONCLUSION

Overall, our data strongly suggested that targeting PRC2 promotes the expression of SFRP1, thereby inhibiting the progression of CCA.

KEY POINTS/HEADLIGHTS

Cholangiocarcinoma (CCA) exhibits elevated expression of EZH2, SUZ12 and EED, resulting in increased levels of H3K27me3. Targeting polycomb repressor complex 2 (PRC2) leads to the removal of H3K27me3 from the secreted frizzled-related protein 1 (SFRP1) promoter and DNA hypomethylation, thereby activating the transcription of SFRP1. Inhibiting PRC2, including the use of EZH2 inhibitors, holds promise as a potential strategy for developing anti-cancer drugs for CCA.

The roles of epigenetic regulation in cholangiocarcinogenesis

Cholangiocarcinoma (CCA), a heterogeneous malignancy of bile duct epithelial cells, is characterized by aggressiveness, difficult diagnosis, and poor prognosis due to limited understanding and lack of effective therapeutic strategies. Genetic and epigenetic alterations accumulated in CCA cells can cause the aberrant regulation of oncogenes and tumor suppressors. Epigenetic alterations with histone modification, DNA methylation, and noncoding RNA modulation are associated with the carcinogenesis of CCA. Mutation or silencing of genes by various mechanisms can be a frequent event during CCA development. Alterations in histone acetylation/deacetylation at the posttranslational level, DNA methylation at promoters, and noncoding RNA regulation contribute to the heterogeneity of CCA and drive tumor development. In this review article, we mainly focus on the roles of epigenetic regulation in cholangiocarcinogenesis. Alterations in epigenetic modification can be potential targets for the therapeutic management of CCA, and epigenetic targets may become diagnostic biomarkers of CCA.

KRAS Hijacks the miRNA Regulatory Pathway in Cancer

Extensive studies have focused on the misregulation of individual miRNAs in cancer. More recently, mutations in the miRNA biogenesis and processing machinery have been implicated in several malignancies. Such mutations can lead to global miRNA misregulation, which may promote many of the well-known hallmarks of cancer. Interestingly, recent evidence also suggests that oncogenic Kristen rat sarcoma viral oncogene homolog (KRAS) mutations act in part by modulating the activity of members of the miRNA regulatory pathway. Here, we highlight the vital role mutations in the miRNA core machinery play in promoting malignant transformation. Furthermore, we discuss how mutant KRAS can simultaneously impact multiple steps of miRNA processing and function to promote tumorigenesis. Although the ability of KRAS to hijack the miRNA regulatory pathway adds a layer of complexity to its oncogenic nature, it also provides a potential therapeutic avenue that has yet to be exploited in the clinic. Moreover, concurrent targeting of mutant KRAS and members of the miRNA core machinery represents a potential strategy for treating cancer.

Chromobox proteins in cancer: Multifaceted functions and strategies for modulation (Review)

Chromobox (CBX) proteins are important epigenetic regulatory proteins and are widely involved in biological processes, such as embryonic development, the maintenance of stem cell characteristics and the regulation of cell proliferation and apoptosis. Disorder and dysfunction of CBXs in cancer usually lead to the blockade or ectoptic activation of developmental pathways, promoting the occurrence, development and progression of cancer. In the present review, the characteristics and functions of CBXs were first introduced. Subsequently, the expression of CBXs in cancers and the relationship between CBXs and clinical characteristics (mainly cancer grade, stage, metastasis and relapse) and prognosis were discussed. Finally, it was described how CBXs regulate cell proliferation and self‑renewal, apoptosis and the acquisition of malignant phenotypes, such as invasion, migration and chemoresistance, through mechanisms involving epigenetic modification, nuclear translocation, noncoding RNA interactions, transcriptional regulation, posttranslational modifications, protein‑protein interactions, signal transduction and metabolic reprogramming. The study also focused on cancer therapies targeting CBXs. The present review provides new insight and a comprehensive basis for follow‑up research on CBXs and cancer.

The H2A.Z-KDM1A complex promotes tumorigenesis by localizing in the nucleus to promote SFRP1 promoter methylation in cholangiocarcinoma cells

Background

Intrahepatic cholangiocarcinoma (ICC), originating from the bile ducts, is the second most common primary liver malignancy, and its incidence has recently increased. H2A.Z, a highly conserved H2A variant, is emerging as a key regulatory molecule in cancer. However, its underlying mechanism of action in ICC cells remains unclear. 

Methods

Here, we examined the expression of H2A.Z and SFRP1 in normal intrahepatic cholangiocytes, ICC cell lines, ICC tissue microarrays, and fresh specimens. The correlations between H2A.Z or SFRP1 expression and clinical features were analysed. The overall survival rate was analysed based on H2A.Z and SFRP1 expression. Immunoprecipitation was used to analyse the recruitment of KDM1A, and ChIP sequencing and BSP were used to analyse the enrichment of methylation-related molecules such as H3K4me1 and H3K4me2 in the SFRP1 promoter and reveal the underlying mechanisms. Knockdown and rescue experiments were used to determine the potential mechanism by which H2A.Z and SFRP1 promote tumorigenesis in vitro.

Results

We showed that upregulation of H2A.Z expression is linked to downregulation of SFRP1 expression in ICC tissues and poor overall survival in patients with ICC. H2A.Z interacted with KDM1A in the nucleus to bind to the -151 ~ -136 bp region upstream of the SFRP1 promoter to increase its demethylation in ICC cells. Functionally, H2A.Z silencing inhibited the proliferation and invasion of ICC cells, and these effects were mitigated by SFRP1 silencing in ICC cells.

Conclusions

Our findings reveal that H2A.Z inhibits SFRP1 expression through chromatin modification in the context of ICC by forming a complex with KDM1A in the nucleus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10279-y.

Dicer-mediated miR-200b expression contributes to cell migratory/invasive abilities and cancer stem cells properties of breast cancer cells

Distant metastasis is the leading cause of death in patients with breast cancer. Despite considerable treatment advances, the clinical outcomes of patients with metastatic breast cancer remain poor. CSCs can self-renew, enhancing cancer progression and metastasis. Dicer, a microRNA (miRNA) processing–related enzyme, is required for miRNA maturation. Imbalanced Dicer expression may be pivotal in cancer progression. However, whether and how Dicer affects the stemness of metastatic breast cancer cells remains unclear. Here, we hypothesized that Dicer regulates the migration, invasion, and stemness of breast cancer cells. We established highly invasive cell lines (MCF-7/I-3 and MDA-MB-231/I-3) and observed that Dicer expression was conspicuously lower in the highly invasive cells than in the parental cells. The silencing of Dicer significantly enhanced the cell migratory/invasive abilities and CSCs properties of the breast cancer cells. Conversely, the overexpression of Dicer in the highly invasive cells reduced their migration, invasion, and CSCs properties. Our bioinformatics analyses demonstrated that low Dicer levels were correlated with increased breast cancer risk. Suppression of Dicer inhibited miR-200b expression, whereas miR-200b suppression recovered Dicer knockdown–induced migration, invasion, and cancer stem cells (CSCs) properties of the breast cancer cells. Thus, our findings reveal that Dicer is a crucial regulator of the migration, invasion, and CSCs properties of breast cancer cells and is significantly associated with poor survival in patients with breast cancer.

Overview of host miRNA properties and their association with epigenetics, long non-coding RNAs, and Xeno-infectious factors

MicroRNA-derived structures play impressive roles in various biological processes. So dysregulation of miRNAs can lead to different human diseases. Recent studies have extended our comprehension of the control of miRNA function and features. Here, we overview some remarkable miRNA properties that have potential implications for the miRNA functions, including different variants of a miRNA called isomiRs, miRNA arm selection/arm switching, and the effect of these factors on miRNA target selection. Besides, we review some aspects of miRNA interactions such as the interaction between epigenetics and miRNA (different miRNAs and their related processing enzymes are epigenetically regulated by multiple DNA methylation enzymes. moreover, DNA methylation could be controlled by diverse mechanisms related to miRNAs), direct and indirect crosstalk between miRNA and lnc (Long Non-Coding) RNAs as a further approach to conduct intercellular regulation called "competing endogenous RNA" (ceRNA) that is involved in the pathogenesis of different diseases, and the interaction of miRNA activities and some Xeno-infectious (virus/bacteria/parasite) factors, which result in modulation of the pathogenesis of infections. This review provides some related studies to a better understanding of miRNA involvement mechanisms and overcoming the complexity of related diseases that may be applicable and useful to prognostic, diagnostic, therapeutic purposes and personalized medicine in the future.

DICER regulates the expression of major satellite repeat transcripts and meiotic chromosome segregation during spermatogenesis

Constitutive heterochromatin at the pericentric regions of chromosomes undergoes dynamic changes in its epigenetic and spatial organization during spermatogenesis. Accurate control of pericentric heterochromatin is required for meiotic cell divisions and production of fertile and epigenetically intact spermatozoa. In this study, we demonstrate that pericentric heterochromatin is expressed during mouse spermatogenesis to produce major satellite repeat (MSR) transcripts. We show that the endonuclease DICER localizes to the pericentric heterochromatin in the testis. Furthermore, DICER forms complexes with MSR transcripts, and their processing into small RNAs is compromised in Dicer1 knockout mice leading to an elevated level of MSR transcripts in meiotic cells. We also show that defective MSR forward transcript processing in Dicer1 cKO germ cells is accompanied with reduced recruitment of SUV39H2 and H3K9me3 to the pericentric heterochromatin and meiotic chromosome missegregation. Altogether, our results indicate that the physiological role of DICER in maintenance of male fertility extends to the regulation of pericentric heterochromatin through direct targeting of MSR transcripts.

Function of Dicer with regard to Energy Homeostasis Regulation, Structural Modification, and Cellular Distribution

As a type III ribonuclease (RNase III) specifically cleaving double-stranded RNA substrates into short fragments, Dicer is indispensable in a range of physi/pathologic processes, e.g., nutrient deprivation, hypoxia, or DNA damage. Therefore, much interest has been paid to the research of this protein as well as its products like microRNAs (miRNAs). The close relationship between Dicer levels and fluctuations of nutrient availability suggests that the protein participates in the regulation of systemic energy homeostasis. Through miRNAs, Dicer regulates the hypothalamic melanocortin-4 system and central autophagy promoting energy expenditure. Moreover, by influencing canonical energy sensors like adenosine monophosphate-activated protein kinase (AMPK) or mammalian target of rapamycin (mTOR), Dicer favors catabolism in the periphery. Taken together, Dicer might be targeted in the control of energy dysregulation. However, factors affecting its RNase activity should be noted. Firstly, modulation of structural integrity affects its role as a ribonuclease. Secondly, although previously known as a cytosolic endoribonuclease, evidence suggests Dicer can relocalize into the nucleus where it could also produce small RNAs. In this review, we probe into involvement of Dicer in energy homeostasis as well as its structural integrity or cellular distribution which affects its ability to produce miRNAs, in the hope of providing novel insights into its mechanism of action for future application.

Bioinformatic screening and experimental analysis identify SFRP1 as a prognostic biomarker for tongue squamous cell carcinomas

OBJECTIVE

To provide a prognostic biomarker and a potential therapeutic target for tongue squamous cell carcinoma (TSCC).

DESIGN

Screening the prognostic genes of TSCC by bioinformatics, and verifying the correlation between the above genes and the prognosis of TSCC by experiments.

RESULTS

Twenty-four common differentially expressed genes (DEGs) between TSCC and the corresponding normal tissues were screened from four sets of TSCC functional gene expression series in Gene Expression Omnibus (GEO) datasets. Further bioinformatics research based on the data from The Cancer Genome Atlas (TCGA), Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) indicate that the low expression of SFRP1 might be correlated with poor prognosis of TSCC patients. By colony formation assay, reverse transcription polymerase chain reaction (RT-PCR), western blotting, immunohistochemical staining, flowcytometry, lentivirus transfection and animal experiments, it was confirmed that the low level of SFRP1 expression correlated with poor prognosis of TSCC patients.

CONCLUSION

This study identified SFRP1 as a novel prognostic biomarker and a potential therapeutic target for TSCC.

CyclinD1 inhibits dicer and crucial miRNA expression by chromatin modification to promote the progression of intrahepatic cholangiocarcinoma

Background

CyclinD1 is crucial for cell cycling and can regulate the expression of Dicer, a crucial regulator of microRNA maturation. However, little is known on how CyclinD1 regulates Dicer and miRNA expression, and the progression of intrahepatic cholangiocarcinoma (ICC).

Methods

The expression of CyclinD1 and Dicer in non-tumor cholangiocytes, ICC cells and tissues as well as their association with clinicopathological characteristics and survival were examined. The potential mechanisms by which CyclinD1 regulates Dicer and relative miRNA expression were determined by immunoprecipitation, ChIP sequence, BSP and luciferase reporter assays following induction of CyclinD1 over-expression or silencing and Dicer silencing. The impact of CyclinD1 and/or Dicer silencing on the growth of ICC was tested in vivo.

Results

Up-regulated CyclinD1 was associated with down-regulated Dicer expression in ICC tissues and poorer overall survival in patients with ICC. CyclinD1 interacted with the nuclear H3K9me3 and SUV39H1 and bound to the Dicer promoter to increase its CpG island methylation in ICC cells. Functionally, CyclinD1 silencing inhibited the malignancy of ICC cells, which were mitigated partially by Dicer silencing in ICC cells. Dicer silencing down-regulated miR-1914-5p and miR-541-5p expression, which targeted and promoted CyclinD1 and CDK6 expression in ICC cells.

Conclusions

Our findings uncover that CyclinD1 inhibits Dicer expression by chromatin modification to reduce miR-1914-5p/miR-541-5p expression, which positively-feedback enhances CyclinD1 and CDK6 expression and progression of ICC.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1415-5) contains supplementary material, which is available to authorized users.

Effects of in ovo injection of vitamin C on heat shock protein and metabolic genes expression

Some studies have shown that the excessive metabolic heat production is the primary cause for dead chicken embryos during late embryonic development. Increasing heat shock protein (HSP) expression and adjusting metabolism are important ways to maintain body homeostasis under heat stress. This study was conducted to investigate the effects of in ovo injection (IOI) of vitamin C (VC) at embryonic age 11th day (E11) on HSP and metabolic genes expression. A total of 320 breeder eggs were randomly divided into normal saline and VC injection groups. We detected plasma VC content and rectal temperature at chick's age 1st day, and the mRNA levels of HSP and metabolic genes in embryonic livers at E14, 16 and 18, analysed the promoter methylation levels of differentially expressed genes and predicted transcription factors at the promoter regions. The results showed that IOI of VC significantly increased plasma VC content and decreased rectal temperature (P < 0.05). In ovo injection of VC significantly increased heat shock protein 60 (HSP60) and pyruvate dehydrogenase kinase 4 (PDK4) genes expression at E16 and PDK4 and secreted frizzled related protein 1 (SFRP1) at E18 (P < 0.05). At E16, IOI of VC significantly decreased the methylation levels of total CpG sites and -336 CpG site in HSP60 promoter and -1137 CpG site in PDK4 promoter (P < 0.05). Potential binding sites for nuclear factor-1 were found around -389 and -336 CpG sites in HSP60 promoter and potential binding site for specificity protein 1 was found around -1137 CpG site in PDK4 promoter. Our results suggested that IOI of VC increased HSP60, PDK4 and SFRP1 genes expression at E16 and 18, which may be associated with the demethylation in gene promoters. Whether IOI of VC could improve hatchability needs to be further verified by setting uninjection group.

Incidence of cancer (other than gastric cancer) in pernicious anaemia: A systematic review with meta-analysis

BACKGROUND

Pernicious anaemia (PA) is associated with increased gastric cancer risk, but the evidence is conflicting regarding the associated risk of other cancers.

AIM

To systematically determine the incidence rates of gastro-intestinal cancers other than gastric cancers (GI-other-than-GC) and non-gastrointestinal cancers (non-GIC) in PA adults, globally and per tumour site, and the risk associated with PA for GI-other than GC and non-GIC.

METHODS

Studies of PA patients reporting the incidence of GI-other-than-GCs and non-GICs were identified with MEDLINE (PubMed)-EMBASE (from first date available to April 2017). A meta-analysis of annual cancer incidence rates was performed. The outcome was the cumulative incidence of GI-other-than-GCs and non-GICs (ratio between the numbers of new cancer cases identified during the follow-up period and the number of PA patients) and the incidence rate expressed as the rate of events-per-time-unit (person-years).

RESULTS

Of 82,257 PA patients, the pooled incidence rates/100 person-years for non-GCs and non-GICs of 0.27 (95% CI:0.16-0.42) and 0.23 (95% CI:0.22-0.25) were calculated by meta-analysis. Compared to the GLOBOCAN data for the general population from the countries of the included studies, the meta-analysis showed an overall relative risk (RR) of cancer in PA of 0.68 (95% CI:0.48-0.95). PA patients had a lower RR of colorectal, breast, liver, oesophageal, lung, thyroid, ovary, non-melanoma skin and kidney cancers but had a higher RR of biliary tract cancer (1.81:1.21-2.70), multiple myeloma (2.83:1.76-4.55), Hodgkin's lymphoma (3.0:1.35-6.68), non-Hodgkin's lymphoma (2.08: 1.58-2.75), and leukaemia (1.56:1.16-2.12).

CONCLUSION

An overall lower RR of cancers-other-than-gastric-cancer in PA patients but an increased RR of biliary tract cancers and haematological malignancies was observed.

From "Cellular" RNA to "Smart" RNA: Multiple Roles of RNA in Genome Stability and Beyond

Coding for proteins has been considered the main function of RNA since the "central dogma" of biology was proposed. The discovery of noncoding transcripts shed light on additional roles of RNA, ranging from the support of polypeptide synthesis, to the assembly of subnuclear structures, to gene expression modulation. Cellular RNA has therefore been recognized as a central player in often unanticipated biological processes, including genomic stability. This ever-expanding list of functions inspired us to think of RNA as a "smart" phone, which has replaced the older obsolete "cellular" phone. In this review, we summarize the last two decades of advances in research on the interface between RNA biology and genome stability. We start with an account of the emergence of noncoding RNA, and then we discuss the involvement of RNA in DNA damage signaling and repair, telomere maintenance, and genomic rearrangements. We continue with the depiction of single-molecule RNA detection techniques, and we conclude by illustrating the possibilities of RNA modulation in hopes of creating or improving new therapies. The widespread biological functions of RNA have made this molecule a reoccurring theme in basic and translational research, warranting it the transcendence from classically studied "cellular" RNA to "smart" RNA.

LZTS2 promoter hypermethylation: a potential biomarker for the diagnosis and prognosis of laryngeal squamous cell carcinoma

BACKGROUND

LZTS2 (leucine zipper tumor suppressor 2), a candidate tumor suppressor gene, suppresses cell growth and plays a vital role in the carcinogenesis and development of tumors. No studies to date have described methylation of the LZTS2 promoter in human cancers, including LSCC (laryngeal squamous cell carcinoma). Therefore, the aim of this study was to explore the relationship between LZTS2 promoter methylation and risk of LSCC.

METHODS

In our study, LZTS2 promoter methylation levels in LSCC tumor and adjacent normal tissues from 96 patients were measured using quantitative methylation-specific polymerase chain reaction (qMSP) assays.

RESULTS

The qMSP analyses revealed that LZTS2 promoter methylation levels in the LSCC tumor samples were significantly higher than those in paired adjacent healthy tissue samples. Furthermore, LZTS2 methylation levels were elevated in smokers, advanced T classified, and clinically staged patients, as well as in patients with lymph node metastases. In addition, Kaplan-Meier survival curves results showed that overall survival of LSCC patients with hypomethylated LZTS2 promoters was significantly higher than that in patients with hyper-methylated LZTS2 promoters (log-rank test P = 0.028). Meanwhile, the area under the receiver operating characteristic curve was 0.920. The diagnostic threshold value for LZTS2 methylation was 11.63% (94.7% sensitivity and 80.4% specificity).

CONCLUSIONS

LZTS2 promoter hypermethylation is associated with risk, progression, and prognosis of LSCC in a cohort of 96 human subjects; LZTS2 promoter hypermethylation is a candidate diagnostic and prognostic biomarker for LSCC.

Nuclear re-localization of Dicer in primary mouse embryonic fibroblast nuclei following DNA damage

Dicer is a key component of RNA interference (RNAi) and well-known for its role in biogenesis of micro (mi)RNA in the cytoplasm. Increasing evidence suggests that mammalian Dicer is also present and active in the nucleus. We have previously shown that phosphorylated human Dicer associates with chromatin in response to DNA damage and processes double-stranded (ds)RNA in the nucleus. However, a recent study by Much et al. investigated endogenously tagged HA-Dicer both in primary mouse embryonic fibroblasts (PMEFs) as well as adult homozygous viable and fertile HA-Dicer mice under physiological conditions and concluded that murine Dicer is exclusively cytoplasmic. The authors challenged several findings, reporting functions of Dicer in mammalian nuclei. We have re-investigated this issue by applying subcellular fractionation, super-resolution microscopy followed by 3D reconstitution, and phospho-Dicer-specific antibodies using the same HA-Dicer PMEF cell line. Our data show that a small fraction of the murine HA-Dicer pool, approximately 5%, localises in the nucleus and is phosphorylated upon DNA damage. We propose that Dicer localisation is dynamic and not exclusively cytoplasmic, particularly in cells exposed to DNA damage.

Physiogenomics in Etiopathogenesis of Cholangiocarcinoma

Objective

Cholangiocarcinoma is a serious malignancy that is very common in the tropical countries. It is a kind of deadly primary hepatobiliary tumor. There is a wide spectrum of tumors with varying differentiation and malignancy grades. Although it has been known for a long time inmmedicine, there is no clear cut that this deadly cancer is genetic disorder or not. A systemic approach on the pathophysiology and genomics can provide useful information and help better understand the pathogenesis of cholangiocarcinoma.

Methods

In this work, a standard bioinformatics physiological genomics analysis of cholangiocarcinoma was performed.

Result

According to this work, there is no identified physiogenomics relationship for the cholangiocarcinoma.

Conclusion

This might imply that the cholangiocarcinoma is directly due to environmental insult. It implies that there should be no specific gene that might contribute to the increased risk in the etiopathogenesis of cholangiocarcinoma.

Nuclear phosphorylated Dicer processes double-stranded RNA in response to DNA damage

The endoribonuclease Dicer is a key component of the human RNA interference pathway and is known for its role in cytoplasmic microRNA production. Recent findings suggest that noncanonical Dicer generates small noncoding RNA to mediate the DNA damage response (DDR). Here, we show that human Dicer is phosphorylated in the platform-Piwi/Argonaute/Zwille-connector helix cassette (S1016) upon induction of DNA damage. Phosphorylated Dicer (p-Dicer) accumulates in the nucleus and is recruited to DNA double-strand breaks. We further demonstrate that turnover of damage-induced nuclear, double-stranded (ds) RNA requires additional phosphorylation of carboxy-terminal Dicer residues (S1728 and S1852). DNA damage-induced nuclear Dicer accumulation is conserved in mammals. Dicer depletion causes endogenous DNA damage and delays the DDR by impaired recruitment of repair factors MDC1 and 53BP1. Collectively, we place Dicer within the context of the DDR by demonstrating a DNA damage-inducible phosphoswitch that causes localized processing of nuclear dsRNA by p-Dicer to promote DNA repair.