Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Biological Sciences, 2009. / Includes bibliographical references (leaves 128-145).

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Computational Biology and Molecular Biophysics." Includes bibliographical references (p. 157-179).

No description available.

Zhang, Zhiyi. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves ). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

The p53 tumor suppressor protein has been well-characterized for its role in inducing growth arrest, senescence, and apoptosis upon various types of stresses. Recently, however, roles of p53 have expanded beyond the canonical functions, and now include cellular processes such as metabolism, oxidative balance, and ferroptosis. Through RNA-seq screening, we first identified phosphoglycerate dehydrogenase (PHGDH), a rate-limiting enzyme in the serine biosynthesis pathway, as a novel metabolic target of p53. p53 suppresses PHGDH expression and inhibits de novo serine biosynthesis. Notably, upon serine starvation, p53-mediated cell death is significantly enhanced in response to Nutlin-3 treatment. Moreover, PHGDH has been demonstrated to be frequently amplified in human melanomas. We found that PHGDH overexpression significantly suppresses the apoptotic response, whereas RNAi-mediated knock-down of endogenous PHGDH promotes apoptosis under the same treatment. Together, our findings demonstrate an important role of p53 in regulating serine biosynthesis through suppressing PHGDH expression, and reveal serine deprivation as a novel approach to sensitize p53-mediated apoptotic responses in human melanoma cells. In addition, we also identified spermidine/spermine N1-acetyltransferase 1 (SAT1) as a novel metabolic target of p53. SAT1 is a rate-limiting enzyme in polyamine catabolism critically involved in the conversion of spermidine and spermine back to putrescine. Surprisingly, we found that activation of SAT1 expression induces lipid peroxidation and sensitizes cells to undergo ferroptosis upon reactive oxygen species (ROS)-induced stress, which also leads to suppression of tumor growth in xenograft tumor models. Notably, SAT1 expression is down-regulated in human tumors, and CRISPR-cas9-mediated knockout of SAT1 partially abrogates p53-mediated ferroptosis. Moreover, SAT1 induction is correlated with the expression levels of arachidonate 15-lipoxygenase (ALOX15), and SAT1-induced ferroptosis is significantly abrogated in the presence of PD146176, a specific inhibitor of ALOX15. Together, these data indicate a novel regulatory role of p53 in polyamine metabolism and provide insight into the regulation of p53-mediated ferroptotic responses. Our studies on PHGDH and SAT1 led us to the question of whether these unconventional functions of p53 contribute to its role as a tumor suppressor. In fact, previous view regarding the mechanism of p53-mediated tumor suppression, which was long thought to be growth arrest, apoptosis, and senescence, has recently been challenged by several knockout and knock-in mouse studies. Previously, we established mice (p533KR/3KR) in which p53 acetylation at lysine residues K117, K161, and K162 were abolished by replacing lysine with arginine. p533KR/3KR mice completely lost p53-mediated cell cycle arrest, apoptosis, and senescence functions in response to stresses. However, unlike p53-null mice which rapidly develop spontaneous thymic lymphomas, all of the p533KR/3KR mice remain tumor-free, indicating that other aspects of p53 functions are sufficient to prevent tumor formation. Notably, p533KR retains the ability to regulate metabolic targets including TIGAR and SAT1, as well as ferroptosis regulator SLC7A11. In this study, we have identified two novel acetylation sites- K98 and K136, in the mouse p53 DNA-binding domain. Whereas loss of K98 or K136 acetylation (p53K98R, p53K136R) alone has modest effect on p53 transcriptional activity, simultaneous mutations at all of these acetylation sites (p534KR98: K98R+3KR, p534KR136: K136R+3KR, p535KR: K98R+K136R+3KR) completely abolish the ability of p53 to regulate TIGAR, SAT1, and SLC7A11. In addition, p534KR98, p534KR136, and p535KR are defective in Erastin-induced ferroptosis. Notably, p534KR98/4KR98, p534KR136/4KR136, and p535KR/5KR knock-in mice lost intact tumor suppression and developed spontaneous tumors. This suggests that p53-mediated ferroptosis may function as a critical barrier to prevent tumor formation independently from growth arrest, apoptosis, and senescence. Interestingly, both p534KR98/4KR98 and p534KR136/4KR136 mice displayed significantly delayed tumorigenesis comparing with p53-null and p535KR/5KR mice. We found that unlike p535KR, p534KR98 retains the capacity to inhibit mammalian target of rapamycin (mTOR) signaling pathway through activating the expression of two mTOR negative regulators, Sestrin2 and DDIT4. Altogether, our findings underscore the extensive scope of p53 functions in metabolic regulation, oxidative stress response, and ferroptosis, and provide novel insights into the tumor suppression mechanism of p53.

研究背景和目的 / 肝癌是非常高死亡率的恶性肿瘤之一。由于传统化疗方式的局限性，表观遗传治疗方法可能成为肝癌治疗的替代方法。研究报道ZBP-89诱导肝癌细胞Bak的表达，表观调控是否参与该诱导作用，目前仍然不清楚。 / HDAC3被认为是化疗靶点和肝癌复发的肿瘤标记物。它常常在肝癌组织中高表达，对HDAC3的抑制作用可以增加肝癌的化疗效果。我们的研究表明ZBP-89可以降低肝癌细胞HDAC3的表达，但机制未明。蛋白的翻译后调控是细胞生化过程的重要调节因素。所以，研究调节HDAC3的降低途径对肝癌的发生和复发具有非常重要的研究意义。 / 本研究旨在研究ZBP-89调控Bak表达的表观遗传机制。同时，弄清楚DNA甲基化转移酶和组蛋白去乙酰化酶是否参与ZBP-89对Bak的调控作用，进一步阐明ZBP-89对HDAC3降低通路的机制。 / 方法和结果 / 肝癌病人组织蛋白分析表明，相对于癌旁组织，肝癌组织Bak和ZBP-89蛋白表达降低，而DNMT1和HDAC3表达升高。免疫共沉淀技术显示ZBP-89与HDAC3、 DNMT1结合，但不与HDAC4， DNMT3a和DNMT3b结合。相应地，HDAC3和 DNMT1免疫沉淀分析也显示三者形成免疫复合物。我们在肝癌细胞中过表达ZBP-89，验证它会不会影响HDACs和DNMTs的活性。实验结果表明过表达的ZBP-89抑制HDACs和DNMTs的活性。进一步发现ZBP-89调节的Bak表达可能是通过抑制HDACs活性和维持组蛋白H3和H4乙酰化水平实现的。另一方面，我们同样证明HDAC的抑制剂（HDACi）VPA和TSA可以诱导肝癌细胞Bak表达，此外，siRNA干扰HDAC3的表达同样可以诱导Bak表达。 / 对DNMT1表达的抑制和使用DNMT抑制剂（DNMTi）Zebularine也可以诱导Bak的表达。染色质免疫沉淀结果显示ZBP-89结合于Bak的启动子区域，从-3188bp到-3183bp，从-275到-49。 ZBP-89可以抑制DNMT的活性，那么ZBP-89是否会影响DNA中CpG岛甲基化状态和甲基化结合蛋白（MeCP2）的结合能力，这一点仍需要进一步证实。结果表明ZBP-89可以抑制MeCP2结合基因组DNA。为进一步揭示MeCP2是否由于启动子区域CpG岛去甲基化影响其结合能力，我们采用亚硫酸盐测序方法。测序结果显示ZBP-89过表达可以影响Bak启动子CpG岛的甲基化状态，并促进其去甲基化。 / 腺病毒介导的ZBP-89过表达降低HDAC3表达呈现剂量依赖性，然而HDAC3 的mRNA水平并没有受到ZBP-89的表达。免疫共沉淀方法和蛋白免疫印迹实验用于分析Pin1和HDAC3复合物，磷酸化IκB和HDAC3复合物的结合情况。结果表明Pin1结合HDAC3并促进HDAC3的减少。同时，HDAC3与磷酸的IκB结合并进入蛋白减少途径。 / 构建的mU6-siPin1表达质粒用于敲除肝癌细胞Pin1的表达，方法检测基因表达水平。Pin1的缺失表达阻碍ZBP-89介导的HDAC3降低。在Pin1 敲除细胞系 JB6 C141 Pin1⁻/⁻ 和Pin1过表达细胞系的研究，ZBP-89更加能促进Pin1⁺/⁺细胞中HDAC3减少，而对Pin1⁺/⁺的细胞则没那么明显。由此肯定了Pin1在ZBP-89介导的HDAC3降低中的重要作用。进一步研究发现， IκB激酶 (IKK)抑制剂，CAY10576，能抑制 ZBP-89介导的HDAC3的降低；而SN50, p65/p50人核抑制多肽，则不影响HDAC3的降低。研究结果证明HDAC3的降低依赖IκB通路，而不是NF- κB活性。 / 我们用人肝癌细胞的裸鼠移植瘤模型研究ZBP-89调控Bak表达的表观遗传机制，及其对肝癌的治疗效果。研究结果表明ZBP-89蛋白和组蛋白抑制剂VPA和DNA甲基化抑制zebularine都能抑制肿瘤的生长，并诱导肿瘤组织Bak表达及细胞凋亡。VPA和zebularine联合治疗的效果更好。研究也表明ZBP-89可以在体内降低HDAC3蛋白水平。 / 结论 / 本研究揭示了ZBP-89调节Bak蛋白表达和肝癌细胞凋亡的表观遗传机制。同时，进一步揭示ZBP-89联合Pin1经由IκB通路调节HDAC3降低的机制. 本研究为肝癌表观遗传学的治疗提供研究基础和科学依据。 / Background / Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies worldwide with a very high mortality. Because the success of the conventional therapies is limited, epigenetic therapy may represent an alternative for HCC management. ZBP-89 is known to induce Bak in HCC. However, it is unclear whether epigenetic mechanisms contribute to ZBP-89-mediated Bak. / Histone acetylase 3 (HDAC3) is realized as a chemotherapy target and a biomarker of recurrence in HCC. HDAC3 is frequently overexpressed in HCC and its inhibition enhances the efficacy of anti-HCC chemotherapy. The pilot data have indicated that ZBP-89 reduced HDAC3 in HCC but the mechanism responsible was unknown. The post-translational modification of proteins functions as a key regulatory factor in cellular physiological procedures, such as ubiquitinoylation degradation. As a biomarker of HCC development and recurrence, it is important to understand how ZBP-89 mediates the reduction of HDAC3. / This study focuses on if ZBP-89 regulates Bak expression through epigenetic mechanisms. It is designed to investigate whether DNA methyltransferases (DNMTs), histone acetylases (HDACs) are involved in regulation of ZBP-89-induced Bak expression. The study also elucidates the mechanism how ZBP-89 reduces the level of HDAC3 protein. / Methods and Results / The levels of Bak and ZBP-89 as shown on western blots were reduced but DNMT1 and HDAC3 were increased in HCC cancer tissues compared to the corresponding non-cancer tissues. Co-immunoprecipitation experiments showed that ZBP-89 bound to HDAC3 and DNMT1 but not other epigenetic enzymes, such as HDAC4, DNMT3a and DNMT3b. To clarify if ZBP-89 affects the activities of HDACs and DNMTs, ZBP-89 was overexpressed in HCC cells. Enzyme activities of HDACs and DNMTs were determined using relevant assay kits. Results showed that overexpressed ZBP-89 inhibited the activities of HDACs and DNMTs. Further experiments indicated that ZBP-89-mediated Bak up-regulation might contribute to maintenance of histone H3 and H4 acetylation through inhibition of HDACs activity. In another set of experiments, we also found an increased Bak expression in HCC cells when the cells were treated with HDAC inhibitors (HDACi) VPA and TSA. HDAC3 siRNA also increased Bak expression. / Both knockdown of DNMT1 expression and administration of DNMTs inhibitors (zebularine) induced Bak expression. Chromatin immunoprecipitation (ChIP) showed that ZBP-89 bound to Bak promoter at the region from -3188bp to -3183bp and from -275 to -49. As ZBP-89 inhibits DNMT activity, it is essential to know whether its inhibition affectes DNA CpG methylation status and methyl-CpG binding protein (MeCP) binding. The results showed that ZBP-89 overexpression inhibited MeCP2 binding to genomic DNA. The finding indicated that decreased MeCP2 binding to DNA might be due to decreased methyl-CpG number in Bak promoter, suggesting that ZBP-89 might affect CpG island methylation status. Therefore, the bisulfite modified DNA sequencing method was used to clarify if Bak promoter CpG island methylation status was altered after ZBP-89 overexpression. Results revealed that ZBP-89 overexpression could demethylate the CpG islands in Bak promoter. / ZBP-89 overexpression dose-dependently reduced the expression of HDAC3 at protein level but not at mRNA level. Co-immunoprecipitation and western blot methods were used to analyze Peptidyl-prolyl cis/trans isomerase 1 (Pin1) and HDAC3, phospho-I kappa B (pIκB), and the result revealed that HDAC3 could bound with either Pin1 or pIκB to promote the reduced expression of HDAC3. / Constructed mU6-siPin1 vector was used to knockdown Pin1 expression in HCC cells. We found that knockdown of Pin1 expression blocked ZBP-89-mediated HDAC3 reduction. Experiments performed in Pin1 allele-knockdown JB6 C141 Pin1⁻/⁻ and Pin1⁺/⁺ cells showed that the reduction of HDAC3 by ZBP-89 was greater in Pin1⁺/⁺ cells than in Pin1⁻/⁻ cells, confirming the role of Pin1 in ZBP-89-mediated HDAC3 reduction. Furthermore, the ZBP-89-mediated HDAC3 reduction was suppressed by CAY10576, an IκB kinase (IKK) activation inhibitor but not by SN50, a p65/p50 translocation inhibitor, suggesting that HDAC reduction may depend on IκB kinase rather than NF-κB activity. / HCC xenograft mouse model was used to support the involvement of epigenetic mechanism in ZBP-89-induced Bak expression and its therapeutic effects against HCC. Results showed that ZBP-89 as well as HDAC inhibitor valproic acid (VPA) or/and DNMT inhibitor zebularine stimulated Bak expression and induced apoptosis of tumor cells in an HCC xenograft mouse model, arresting tumor growth. In HCC xenografe model, treatment by injection of Ad-ZBP-89 viral expression vector mediated ZBP-89 expression decreased HDAC3 expression, but not HDAC4. / Conclusions / In conclusion, the study demonstrates a novel mechanism through which ZBP-89 mediates an epigenetic pathway to promote Bak expression, and induce apoptosis in HCC cells. It also reveals the mechanism of HDAC3 reduction by ZBP-89 is dependent on IκB, which requires the presence of Pin1. This pathway may help develop future epigenetic therapy against HCC. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Ye, Caiguo. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 123-140). / Abstracts also in Chinese. / Abstract --- p.i / 摘要 --- p.v / Publications --- p.viii / Acknowledgements --- p.ix / Abbreviations --- p.xi / List of Tables --- p.xiii / List of figures --- p.xiv / Chapter Chapter One: --- General Introduction --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.2 --- The complexity of HDAC family and functions --- p.3 / Chapter 1.2.1 --- HDAC family --- p.4 / Chapter 1.2.2 --- Multifunction of HDACs --- p.6 / Chapter 1.3 --- HDACs and apoptosis --- p.6 / Chapter 1.3.1 --- HDAC regulates apoptotic-related gene expression --- p.9 / Chapter 1.3.2 --- HDACs regulate apoptosis through protein complexes --- p.18 / Chapter 1.3.3 --- HDACs mediates non-histone deacetylation and apoptosis --- p.21 / Chapter 1.3.4 --- HDACs degradation deficiency and apoptosis --- p.24 / Chapter 1.4 --- DNMTs and epigenetic modification --- p.25 / Chapter 1.4.1 --- DNMT family --- p.25 / Chapter 1.4.2 --- CpG islands methylation and HCC --- p.26 / Chapter 1.5 --- Perspectives --- p.28 / Chapter Chapter Two: --- ZBP-89 up-regulates Bak expression through inhibition the activity of HDACs and DNMTs --- p.30 / Chapter 2.1 --- Introduction --- p.31 / Chapter 2.2 --- Materials and Methods --- p.33 / Chapter 2.2.1 --- Hepatocellular carcinoma patient samples and cell lines --- p.33 / Chapter 2.2.2 --- Chemicals and reagents --- p.34 / Chapter 2.2.3 --- Cell proliferation --- p.34 / Chapter 2.2.4 --- Adenovirus infection of cells --- p.35 / Chapter 2.2.5 --- Apoptosis detection --- p.36 / Chapter 2.2.6 --- Transfection of siRNA and plasmid --- p.36 / Chapter 2.2.7 --- Co-immunoprecipitation (co-IP) --- p.37 / Chapter 2.2.8 --- Western blotting --- p.37 / Chapter 2.2.9 --- Immunohistochemistry and Immunofluorescence --- p.38 / Chapter 2.2.10 --- Chromatin immunoprecipitation --- p.38 / Chapter 2.2.11 --- Sodium bisulfite modified sequencing of Bak promoter --- p.40 / Chapter 2.2.12 --- Histone deacetylase activity assay --- p.41 / Chapter 2.2.13 --- DNA methyltransferases enzyme activity --- p.42 / Chapter 2.2.14 --- Xenograft animal model --- p.43 / Chapter 2.2.15 --- Statistical analysis --- p.43 / Chapter 2.3 --- Results --- p.45 / Chapter 2.3.1 --- ZBP-89 interacts with DNMT1 and HDAC3 --- p.45 / Chapter 2.3.2 --- DNA methyltransferase-1 and histone deacetylase 3 are overexpressed in cancer tissues --- p.48 / Chapter 2.3.3 --- Inhibition of HDACs and DNMTs induces Bak expression and apoptosis --- p.58 / Chapter 2.3.4 --- Adenovirus mediated ZBP-89 expression inhibits HDACs activity --- p.65 / Chapter 2.3.5 --- ZBP-89 suppresses DNMTs activity --- p.67 / Chapter 2.3.6 --- Overexpressed ZBP-89 demethylates methyl-CpG islands --- p.69 / Chapter 2.3.7 --- Downregulation of HDAC3 and DNMT1 enhances Bak expression --- p.74 / Chapter 2.3.8 --- Xenograft nude mouse model reveals that Ad-ZBP-89 adenovirus diminishes tumor volume and induces Bak expression and apoptosis --- p.75 / Chapter 2.4 --- Discussion --- p.81 / Chapter Chapter Three: --- ZBP-89 targets IkappaB to reduce HDAC3 via a Pin1-dependent pathway --- p.86 / Chapter 3.1 --- Introduction --- p.87 / Chapter 3.2 --- Materials and Methods --- p.89 / Chapter 3.2.1 --- Cell lines, chemicals and reagents --- p.89 / Chapter 3.2.2 --- Transfection of siRNA plasmid --- p.89 / Chapter 3.2.3 --- Plasmid extraction by mini-prep --- p.90 / Chapter 3.2.4 --- Co-immunoprecipitation (co-IP) and Western blotting --- p.91 / Chapter 3.2.5 --- Total RNA extraction --- p.92 / Chapter 3.2.6 --- Reverse transcription and real-time PCR --- p.93 / Chapter 3.2.7 --- Immunohistochemistry and Immunofluorescence --- p.94 / Chapter 3.2.8 --- Xenograft animal model --- p.95 / Chapter 3.2.9 --- Statistical analysis --- p.95 / Chapter 3.3 --- Results --- p.97 / Chapter 3.3.1 --- ZBP-89 overexpression diminishes HDAC3 expression but not HDAC4 --- p.97 / Chapter 3.3.2 --- Knockdown of Pin1 blocks ZBP-89-mediated HDAC3 reduction --- p.99 / Chapter 3.3.3 --- ZBP-89 reduces the level of IκB --- p.103 / Chapter 3.3.4 --- IκB degradation inhibitors suppresses ZBP-89-meditaed HDAC3 reduction --- p.105 / Chapter 3.3.5 --- ZBP-89 decreases HDAC3 but increases Bak in xenograft tumor tissues --- p.111 / Chapter 3.4 --- Discussion --- p.115 / Chapter Chapter Four: --- Conclusions and Future Perspectives --- p.119 / Chapter 4.1 --- Summary of results --- p.120 / Chapter 4.2 --- Conclusions --- p.121 / Chapter 4.3 --- Future Perspectives --- p.121 / References --- p.123

The development of resistance to chemotherapeutic drugs is the main obstacle to the successful treatment of many cancers, including childhood neuroblastoma, the most common solid tumour of infants. One factor that may play a role in determining response of neuroblastoma tumours to therapeutic agents is the p53 tumour suppressor gene. A number of previous studies have suggested that this tumour suppressor protein is inactive in neuroblastoma due to its cytoplasmic sequestration. This thesis therefore has examined the functionality of p53 and its role in determining drug response of neuroblastoma cells. An initial study was undertaken that characterised an unusually broad multidrug resistance (MDR) phenotype of a neuroblastoma cell line (IMR/KAT100). The results demonstrated that the MDR phenotype of the IMR/KAT100 cells was associated with the acquisition of mutant p53. To explore the role of p53 in drug resistance further, p53-deficient variants in cell lines with wild-type p53 were generated by transduction of p53-suppressive constructs encoding either shRNA or a dominant-negative p53 mutant. Analysis of these cells indicated that: (i) in contrast to previous reports, wild-type p53 was fully functional in all neuroblastoma lines tested, as evidenced by its activation and nuclear translocation in response to DNA damage, transactivation of target genes and control of cell cycle checkpoints; (ii) inactivation of p53 in neuroblastoma cells resulted in establishment of an MDR phenotype; (iii) knockdown of mutant p53 did not revert the drug resistance phenotype, suggesting it is determined by loss of wild-type function rather than gain of mutant function; (iv) p53-dependent cell senescence, the primary response of S-type neuroblastoma cells to DNA damage, is replaced, after p53 inactivation, by mitotic catastrophe and subsequent apoptosis. In contrast to neuroblastoma, p53 suppression had no effect or increased drug susceptibility in several other tumour cell types, indicating the importance of tissue context for p53- mediated modulation of tumour cell sensitivity to treatment. Taken together, these data provide strong evidence for p53 having a role in mediating drug resistance in neuroblastoma and suggest that p53 status may be an important prognostic marker of treatment response in this disease.

Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains viii, 124 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.