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Articles by Ying Zhao
Total Records ( 5 ) for Ying Zhao
  Lei Nie , S. Scott Perry , Ying Zhao , Jiaxue Huang , Paul W. Kincade , Michael A. Farrar and Xiao-Hong Sun
  Notch signaling pathways exert diverse biological effects depending on the cellular context where Notch receptors are activated. How Notch signaling is integrated with environmental cues is a central issue. Here, we show that Notch activation accelerates ubiquitin-mediated and mitogen-activated protein kinase (MAPK)-dependent degradation of E2A transcription factors and Janus kinases, molecules essential for both B- and T-lymphocyte development. However, these events occur in B lymphocytes, but not T lymphocytes, due to their different levels of MAPK, thus providing one mechanism whereby Notch inhibits B-cell development without impairing T-cell differentiation. Lymphoid progenitors expressing a Notch-resistant E2A mutant differentiated into B-lineage cells on stromal cells expressing Notch ligands and in the thymus of transplant recipients. Bone marrow transplant assays and examination of steady-state B lymphopoiesis also revealed that the expression of Notch-resistant E2A and constitutively active STAT5 in mice neutralized the effects of Notch-induced degradation, allowing B-cell development through a bone marrow-like program in the thymus. These findings illustrate that Notch function can be influenced by MAPKs, producing distinct outcomes in different cellular contexts.
  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.
  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.

  Ying Zhao , Qinghua Fang , Susanne G. Straub and Geoffrey W. G. Sharp
  The effects of norepinephrine (NE), an inhibitor of insulin secretion, were examined on membrane potential and the ATP-sensitive K+ channel (KATP) in INS 832/13 cells. Membrane potential was monitored under the whole cell current clamp mode. NE hyperpolarized the cell membrane, an effect that was abolished by tolbutamide. The effect of NE on KATP channels was investigated in parallel using outside-out single channel recording. This revealed that NE enhanced the open activities of the KATP channels ∼2-fold without changing the single channel conductance, demonstrating that NE-induced hyperpolarization was mediated by activation of the KATP channels. The NE effect was abolished in cells preincubated with pertussis toxin, indicating coupling to heterotrimeric Gi/Go proteins. To identify the G proteins involved, antisera raised against α and β subunits (anti-Gαcommon, anti-Gβ, anti-Gαi1/2/3, and anti-Gαo) were used. Anti-Gαcommon totally blocked the effects of NE on membrane potential and KATP channels. Individually, anti-Gαi1/2/3 and anti-Gαo only partially inhibited the action of NE on KATP channels. However, the combination of both completely eliminated the action. Antibodies against Gβ had no effects. To confirm these results and to further identify the G protein subunits involved, the blocking effects of peptides containing the sequence of 11 amino acids at the C termini of the α subunits were used. The data obtained were similar to those derived from the antibody work with the additional information that Gαi3 and Gαo1 were not involved. In conclusion, both Gi and Go proteins are required for the full effect of norepinephrine to activate the KATP channel.
  Jianrong Wang , Huiqin Lian , Ying Zhao , Mara A. Kauss and Samantha Spindel
  Vitamin D3 causes potent suppression of various cancer cells; however, significant supraphysiological concentrations of this compound are required for antineoplastic effects. Current combinatorial therapies with vitamin D3 are restricted to differentiation effects. It remains uncertain if autophagy is involved in vitamin D3 inhibition on leukemia cells. Here we show that besides triggering differentiation and inhibiting apoptosis, which was previously known, vitamin D3 triggers autophagic death in human myeloid leukemia cells. Inhibiting differentiation does not efficiently diminish vitamin D3 suppression on leukemia cells. Vitamin D3 up-regulates Beclin1, which binds to class III phosphatidylinositol 3-kinase to trigger autophagy. Vitamin D3 phosphorylates Bad in its BH3 domain, resulting in disassociation of the apoptotic Bad-Bcl-xL complex and association of Bcl-xL with Beclin1 and ultimate suppression of apoptotic signaling. Knockdown of Beclin1 eliminates vitamin D3-induced autophagy and inhibits differentiation but activates apoptosis, suggesting that Beclin1 is required for both autophagy and differentiation, and autophagy cooperates with differentiation but excludes apoptosis, in which Beclin1 acts as an interface for these three different cascades. Moreover, additional up-regulation of autophagy, but not apoptosis, dramatically improves vitamin D3 inhibition on leukemia cells. These findings extend our understanding of the action of vitamin D3 in antineoplastic effects and the role of Beclin1 in regulating multiple cellular cascades and suggest a potentially promising strategy with a significantly better antileukemia effect.
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