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Articles by Lian Li
Total Records ( 3 ) for Lian Li
  Li-Peng Wu , Xi Wang , Lian Li , Ying Zhao , Shaoli Lu , Yu Yu , Wen Zhou , Xiangyu Liu , Jing Yang , Zhixin Zheng , Hui Zhang , Jingnan Feng , Yang Yang , Haiying Wang and Wei-Guo Zhu
  Histone deacetylase inhibitor (HDACi) has been shown to demethylate the mammalian genome, which further strengthens the concept that DNA methylation and histone modifications interact in regulation of gene expression. Here, we report that an HDAC inhibitor, depsipeptide, exhibited significant demethylating activity on the promoters of several genes, including p16, SALL3, and GATA4 in human lung cancer cell lines H719 and H23, colon cancer cell line HT-29, and pancreatic cancer cell line PANC1. Although expression of DNA methyltransferase 1 (DNMT1) was not affected by depsipeptide, a decrease in binding of DNMT1 to the promoter of these genes played a dominant role in depsipeptide-induced demethylation and reactivation. Depsipeptide also suppressed expression of histone methyltransferases G9A and SUV39H1, which in turn resulted in a decrease of di- and trimethylated H3K9 around these genes` promoter. Furthermore, both loading of heterochromatin-associated protein 1 (HP1α and HP1β) to methylated H3K9 and binding of DNMT1 to these genes` promoter were significantly reduced in depsipeptide-treated cells. Similar DNA demethylation was induced by another HDAC inhibitor, apicidin, but not by trichostatin A. Our data describe a novel mechanism of HDACi-mediated DNA demethylation via suppression of histone methyltransferases and reduced recruitment of HP1 and DNMT1 to the genes` promoter.
  Choon-Myung Lee , Bong-Yoon Kim , Lian Li and Edward T. Morgan
  Exposure to inflammatory agents or cytokines causes the suppression of cytochrome P450 (CYP) enzyme activities and expression in liver and primary hepatocyte cultures. We showed previously that phenobarbital-induced CYP2B protein is down-regulated in primary cultures of rat hepatocytes after exposure to bacterial endotoxin (lipopolysaccharide) in a nitric oxide (NO) -dependent manner. In this study, we found that CYP2B proteins in primary rat hepatocyte cultures were suppressed >60% after 6 h of treatment with interleukin-1β (IL-1). This effect was NO-dependent, and treatment of cells with the NO donors (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl) aminodiazen-1-ium-1,2-diolate (NOC-18), S-nitrosoglutathione, and S-nitroso-N-acetylpenicillamine also suppressed CYP2B proteins. However, the down-regulation by IL-1 was insensitive to inhibition of cGMP-dependent protein kinases. The down-regulation by IL-1 or NO donors was abolished by treatments with the proteasome inhibitors MG132 and lactacystin that did not affect NO production. The calpain inhibitor E64-d or the lysosomal protease inhibitors NH4Cl and chloroquine did not attenuate the down-regulation of CYP2B by IL-1. Treatment of HeLa cells expressing c-Myc-tagged CYP2B1 with NOC-18 down-regulated its expression and enhanced its ubiquitination. Treatment of rat liver microsomes with S-nitrosoglutathione caused S-nitrosylation of CYP2B protein and enhanced the ubiquitination pattern of CYP2B compared with unmodified CYP2B in an in vitro ubiquitination assay. These data are consistent with the hypothesis that NO-dependent CYP2B ubiquitination and proteasomal degradation are dependent on protein modification by reactive nitrogen species.

  Haiying Wang , Ying Zhao , Lian Li , Michael A. McNutt , Lipeng Wu , Shaoli Lu , Yu Yu , Wen Zhou , Jingnan Feng , Guolin Chai , Yang Yang and Wei-Guo Zhu
  Most agents that damage DNA act through posttranslational modifications of p53 and activate its downstream targets. However, whether cellular responses to nucleoside analogue-induced DNA damage also operate through p53 posttranslational modification has not been reported. In this study, the relationship between p53 activation and its posttranslational modifications was investigated in the human cancer cell lines A549 and HCT116 in response to 5-aza-2`-deoxycytidine (5-aza-CdR) or cytarabine treatment. 5-Aza-CdR induces p53 posttranslational modifications through activation of an ATM- and Rad3-related (ATR) signaling pathway, and 5-aza-CdR-induced association of replication protein A with chromatin is required for the binding of ATR to chromatin. Upon treatment with 5-aza-CdR, ATR activation is clearly associated with p53 phosphorylation at Ser15, but not at Thr18, Ser20, or Ser37. This specific p53 phosphorylation at Ser15 in turn results in acetylation of p53 at Lys320 and Lys373/Lys382 through transcriptional cofactors p300/CBP-associated factor and p300, respectively. These p53 posttranslational modifications are directly responsible for 5-aza-CdR induced p21Waf1/Cip1 expression because the binding activity of acetylated p53 at Lys320/Lys373/Lys382 to the p21Waf1/Cip1 promoter, as well as p21Waf1/Cip1 expression itself are significantly increased after 5-aza-CdR treatment. It is of interest that p53 phosphorylation at Ser15 and acetylations at Lys320/Lys373/Lys382 mutually interact in the 5-aza-CdR induced p21Waf1/Cip1 expression shown by transfection of artificially mutated p53 expression vectors including S15A, K320R, and K373R/K382R into p53-null H1299 cells. These data taken together show for the first time that 5-aza-CdR activates the ATR signaling pathway, which elicits a specific p53 phosphorylation-acetylation cascade to induce p21Waf1/Cip1 expression.

 
 
 
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