AIM： To explore the relationship between DNA methyltransferase 1 （DNMT1） and hepatitis B virus （HBV）-related hepatocellular carcinoma （HCC） and its biological significance in primary HCC. METHODS： We carried o...AIM： To explore the relationship between DNA methyltransferase 1 （DNMT1） and hepatitis B virus （HBV）-related hepatocellular carcinoma （HCC） and its biological significance in primary HCC. METHODS： We carried out an immunohistochemical examination of DNMT1 in both HCC and paired nonneoplastic liver tissues from Chinese subjects. DNMT1 mRNA was further examined in HCC cell lines by real-time PCR. We inhibited DNMT1 using siRNA and detected the effect of depletion of DNMT1 on cell proliferation ability and cell apoptosis in the HCC celt line SMMC-7721. RESULTS： DNMT1 protein expression was increased in HCCs compared to histologically normal nonneoplastic liver tissues and the incidence of DNMT1 immunoreactivity in HCCs correlated significantly with poor tumor differentiation （P = 0.014）. There were more cases with DNMT1 overexpression in HCC with HBV （42.85%） than in HCC without HBV （28.57%）. However, no significant difference in DNMT1 expression was found in HBV-positive and HBV-negative cases in the Chinese HCC group. There was a trend that DNMT1 RNA expression increased more in HCC cell lines than in pericarcinoma cell lines and normal liver cell lines. In addition, we inhibited DNMT1 using siRNA in the SMMC-7721 HCC cell line and found depletion of DNMT1 suppressed cells growth independent of expression of proliferating cell nuclear antigen （PCNA）, even in HCC cell lines where DNMT1 was stably decreased. CONCLUSION： The findings implied that DNMT1 plays a key role in HBV-retated hepatocellular tumorigenesis. Depletion of DNMT1 mediates growth suppression in SMMC-7721 cells.展开更多
Global DNA hypomethylation at CpG islands coupled with local hypermethylation is a hallmark for breast cancer, yet the mechanism underlying this change remains elusive. In this study, we showed that DNMT1, which encod...Global DNA hypomethylation at CpG islands coupled with local hypermethylation is a hallmark for breast cancer, yet the mechanism underlying this change remains elusive. In this study, we showed that DNMT1, which encodes a methylation maintenance enzyme, is a transcriptional target of BRCA1. BRCA1 binds to the promoter of the DNMT1 gene through a potential OCT1 site and the binding is required for maintaining a transcriptional active configuration of the promoter in both mouse and human cells. We further demonstrated that impaired function of BRCA1 leads to global DNA hypomethylation, loss of genomic imprinting, and an open chromatin configuration in several types of tissues examined in a BRCA1 mutant mouse model at premaligant stages. BRCA1 deficiency is also associated with significantly increased expression levels of several protooncogenes, including c-Fos, Ha-Ras, and c-Myc, with a higher expression in tumors, while premalignant mammary epithelial cells displayed an intermediate state between tumors and controls. In human clinical samples, reduced expression of BRCA1 correlates with decreased levels of DNMT1, and reduced methylation of CpG islands. Thus, BRCA1 prevents global DNA hypomethylation through positively regulating DNMT1 expression, and this provides one of mechanisms for BRCAl-associated breast cancer formation.展开更多
Objective： To better understand the contribution of dysregulated DNA methyltransferase 1 （DNMT1） expression to the progression and biology of clear cell renal cell carcinoma （ccRCC）. Methods： We examined the dif...Objective： To better understand the contribution of dysregulated DNA methyltransferase 1 （DNMT1） expression to the progression and biology of clear cell renal cell carcinoma （ccRCC）. Methods： We examined the differences in the expression of DNMT1 in 89 ecRCC and 22 normal tissue samples by immunohistochemistry. In addition, changes in cell viability, apoptosis, colony formation and invading ability of ccRCC cell lines （786-0 and Caki-1） were assessed after transfection with DNMT1 siRNA. Results： We found DNMT1 protein was significantly higher expressed in ccRCC than that of in no-tumor tissues （56.2% and 27.3%, respectively, P=0.018）. The expression of DNMT1 was strongly associated with ccRCC tumor size, tumor pathology stage, histological grading, lymph node metastasis, vascular invasion, recurrence and prognosis. Moreover, knockdown of DNMT1 expression significantly inhibited ccRCC cell viability, induced apoptosis, decreased colony formation and invading ability. Conclusions： Expression of DNMTI protein is increased in ccRCC tissues, and DNMT1 expression is associated with poor prognosis of patients. Experiments in vitro further showed DNMT1 played an essential role in proliferation and invasion of renal cancer cells. Moreover, targeting this enzyme could be a promising strategy for treating ccRCC, as evidenced by inhibited cell viability, increased apoptosis, decreased colony formation and invading ability.展开更多
This study was designed to clone cDNA of goat DNA methyltransferase 1（DNMT1） gene,to screen an effective shRNAproducing vector targeting goat DNA methyltransferase 1 and to improve the developmental competence of go...This study was designed to clone cDNA of goat DNA methyltransferase 1（DNMT1） gene,to screen an effective shRNAproducing vector targeting goat DNA methyltransferase 1 and to improve the developmental competence of goat nuclear transfer embryos by decreasing the DNMT1 expression in donor cells.In this study,PCR primers were designed against regions of high homology between bovine and sheep sequences and then used to amplify the larger portions of the coding regions.Next,3 RNAi oligonucleotides were designed based on the cloned sequences and inserted into pRNAT-U6.1/Neo vector,acquiring 3 new vectors,respectively termed pRNAD1,pRNAD2 and pRNAD3.Then the positive cells were sorted by flow cytometry after transfection and detected by real-time PCR analysis and sodium bisulfite genomic sequencing.Finally,the developmental rates of nuclear transfer（NT） embryos generated using donor cells with and without the effective shRNA vector respectively,as well as in vitro fertilization（IVF） embryos were observed and recorded.The results showed that the coding regions of goat DNA methyltransferase 1 gene was successfully cloned（GenBank no.FJ617538）.Furthermore,an effective interfering shRNA（pRNAD2） was obtained,with its interference effect being 47.88%.Finally,NT embryos with shRNA vector harbored better developmental competence during morula and blastocyst stage compared to controls（P 〈 0.05）,reaching the similar rates to IVF embryos（P 〉 0.05）.In conclusion,goat DNA methyltransferase 1 gene cDNA was cloned and sequenced,an effective shRNA vector responsible for inhibiting DNA methyltransferase 1 expression was developed and the developmental competence of goat nuclear transfer morulae and blastcysts was significantly improved,which provided a feasible pathway for improving goat nuclear transfer embryo development competence by decreasing the methylation level in donor cells through RNAi-mediated manner.展开更多
DNA methylation is an important epigenetic regulatory mechanism that influences genomic stability, gene activation, X-chromosome inactivation and other factors. A change in DNA methylation is usually associated with a...DNA methylation is an important epigenetic regulatory mechanism that influences genomic stability, gene activation, X-chromosome inactivation and other factors. A change in DNA methylation is usually associated with aging and cellular senescence. DNA methyltransferase 1(DNMT1) is the most abundant DNA methyltransferase, and it plays an important role in maintaining the established methylation pattern during DNA replication in vertebrates. Although the effect of aging on DNA methylation has been well studied in vertebrates, little research has been conducted in invertebrates, especially in marine bivalves. In this study, we examined global DNA methylation levels in four groups of adult Zhikong scallop Chlamys farreri at different ages. The results showed that both the age and tissue type had a strong effect on the DNA methylation. In addition, a significant decrease in DNA methylation with aging(1–4 years) can be detected in mantle, kidney and hepatopancreas. We further measured the change in DNMT1 transcript abundance using quantitative reverse transcription PCR(q RT-PCR), which revealed that DNMT1 transcription significantly decreased with aging in mantle and hepatopancreas and strongly correlated with DNA methylation(R = 0.72). Our data provided greater insight into the aging-related decline of DNA methylation, which could aid in gaining a better understanding of the relationship between DNA methylation and the aging process in bivalve mollusks.展开更多
基金Supported by National Natural Science Foundation of China,No.30470950
文摘AIM： To explore the relationship between DNA methyltransferase 1 （DNMT1） and hepatitis B virus （HBV）-related hepatocellular carcinoma （HCC） and its biological significance in primary HCC. METHODS： We carried out an immunohistochemical examination of DNMT1 in both HCC and paired nonneoplastic liver tissues from Chinese subjects. DNMT1 mRNA was further examined in HCC cell lines by real-time PCR. We inhibited DNMT1 using siRNA and detected the effect of depletion of DNMT1 on cell proliferation ability and cell apoptosis in the HCC celt line SMMC-7721. RESULTS： DNMT1 protein expression was increased in HCCs compared to histologically normal nonneoplastic liver tissues and the incidence of DNMT1 immunoreactivity in HCCs correlated significantly with poor tumor differentiation （P = 0.014）. There were more cases with DNMT1 overexpression in HCC with HBV （42.85%） than in HCC without HBV （28.57%）. However, no significant difference in DNMT1 expression was found in HBV-positive and HBV-negative cases in the Chinese HCC group. There was a trend that DNMT1 RNA expression increased more in HCC cell lines than in pericarcinoma cell lines and normal liver cell lines. In addition, we inhibited DNMT1 using siRNA in the SMMC-7721 HCC cell line and found depletion of DNMT1 suppressed cells growth independent of expression of proliferating cell nuclear antigen （PCNA）, even in HCC cell lines where DNMT1 was stably decreased. CONCLUSION： The findings implied that DNMT1 plays a key role in HBV-retated hepatocellular tumorigenesis. Depletion of DNMT1 mediates growth suppression in SMMC-7721 cells.
文摘Global DNA hypomethylation at CpG islands coupled with local hypermethylation is a hallmark for breast cancer, yet the mechanism underlying this change remains elusive. In this study, we showed that DNMT1, which encodes a methylation maintenance enzyme, is a transcriptional target of BRCA1. BRCA1 binds to the promoter of the DNMT1 gene through a potential OCT1 site and the binding is required for maintaining a transcriptional active configuration of the promoter in both mouse and human cells. We further demonstrated that impaired function of BRCA1 leads to global DNA hypomethylation, loss of genomic imprinting, and an open chromatin configuration in several types of tissues examined in a BRCA1 mutant mouse model at premaligant stages. BRCA1 deficiency is also associated with significantly increased expression levels of several protooncogenes, including c-Fos, Ha-Ras, and c-Myc, with a higher expression in tumors, while premalignant mammary epithelial cells displayed an intermediate state between tumors and controls. In human clinical samples, reduced expression of BRCA1 correlates with decreased levels of DNMT1, and reduced methylation of CpG islands. Thus, BRCA1 prevents global DNA hypomethylation through positively regulating DNMT1 expression, and this provides one of mechanisms for BRCAl-associated breast cancer formation.
基金supported by grants from National Natural Science Foundation of China (No. 30873097)
文摘Objective： To better understand the contribution of dysregulated DNA methyltransferase 1 （DNMT1） expression to the progression and biology of clear cell renal cell carcinoma （ccRCC）. Methods： We examined the differences in the expression of DNMT1 in 89 ecRCC and 22 normal tissue samples by immunohistochemistry. In addition, changes in cell viability, apoptosis, colony formation and invading ability of ccRCC cell lines （786-0 and Caki-1） were assessed after transfection with DNMT1 siRNA. Results： We found DNMT1 protein was significantly higher expressed in ccRCC than that of in no-tumor tissues （56.2% and 27.3%, respectively, P=0.018）. The expression of DNMT1 was strongly associated with ccRCC tumor size, tumor pathology stage, histological grading, lymph node metastasis, vascular invasion, recurrence and prognosis. Moreover, knockdown of DNMT1 expression significantly inhibited ccRCC cell viability, induced apoptosis, decreased colony formation and invading ability. Conclusions： Expression of DNMTI protein is increased in ccRCC tissues, and DNMT1 expression is associated with poor prognosis of patients. Experiments in vitro further showed DNMT1 played an essential role in proliferation and invasion of renal cancer cells. Moreover, targeting this enzyme could be a promising strategy for treating ccRCC, as evidenced by inhibited cell viability, increased apoptosis, decreased colony formation and invading ability.
基金funded by the Key Scientific and Technological Special Program of China (2008ZX08007004)
文摘This study was designed to clone cDNA of goat DNA methyltransferase 1（DNMT1） gene,to screen an effective shRNAproducing vector targeting goat DNA methyltransferase 1 and to improve the developmental competence of goat nuclear transfer embryos by decreasing the DNMT1 expression in donor cells.In this study,PCR primers were designed against regions of high homology between bovine and sheep sequences and then used to amplify the larger portions of the coding regions.Next,3 RNAi oligonucleotides were designed based on the cloned sequences and inserted into pRNAT-U6.1/Neo vector,acquiring 3 new vectors,respectively termed pRNAD1,pRNAD2 and pRNAD3.Then the positive cells were sorted by flow cytometry after transfection and detected by real-time PCR analysis and sodium bisulfite genomic sequencing.Finally,the developmental rates of nuclear transfer（NT） embryos generated using donor cells with and without the effective shRNA vector respectively,as well as in vitro fertilization（IVF） embryos were observed and recorded.The results showed that the coding regions of goat DNA methyltransferase 1 gene was successfully cloned（GenBank no.FJ617538）.Furthermore,an effective interfering shRNA（pRNAD2） was obtained,with its interference effect being 47.88%.Finally,NT embryos with shRNA vector harbored better developmental competence during morula and blastocyst stage compared to controls（P 〈 0.05）,reaching the similar rates to IVF embryos（P 〉 0.05）.In conclusion,goat DNA methyltransferase 1 gene cDNA was cloned and sequenced,an effective shRNA vector responsible for inhibiting DNA methyltransferase 1 expression was developed and the developmental competence of goat nuclear transfer morulae and blastcysts was significantly improved,which provided a feasible pathway for improving goat nuclear transfer embryo development competence by decreasing the methylation level in donor cells through RNAi-mediated manner.
基金supported by the National Natural Science Foundation of China(31130054)the National High Technology Research and Development Program of China(2012AA10A401)Doctoral Fund of Ministry of Education of China(20120132130002)
文摘DNA methylation is an important epigenetic regulatory mechanism that influences genomic stability, gene activation, X-chromosome inactivation and other factors. A change in DNA methylation is usually associated with aging and cellular senescence. DNA methyltransferase 1(DNMT1) is the most abundant DNA methyltransferase, and it plays an important role in maintaining the established methylation pattern during DNA replication in vertebrates. Although the effect of aging on DNA methylation has been well studied in vertebrates, little research has been conducted in invertebrates, especially in marine bivalves. In this study, we examined global DNA methylation levels in four groups of adult Zhikong scallop Chlamys farreri at different ages. The results showed that both the age and tissue type had a strong effect on the DNA methylation. In addition, a significant decrease in DNA methylation with aging(1–4 years) can be detected in mantle, kidney and hepatopancreas. We further measured the change in DNMT1 transcript abundance using quantitative reverse transcription PCR(q RT-PCR), which revealed that DNMT1 transcription significantly decreased with aging in mantle and hepatopancreas and strongly correlated with DNA methylation(R = 0.72). Our data provided greater insight into the aging-related decline of DNA methylation, which could aid in gaining a better understanding of the relationship between DNA methylation and the aging process in bivalve mollusks.
