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A number of protein kinases have been shown to undergo autophosphorylation, but few have demonstrated a coordinate increase or decrease in enzymatic activity as a result. Described here is a novel S6 kinase isolated from human placenta which autoactivates through autophosphorylation in vitro. This S6/H4 kinase, purified in an inactive state, was shown to be a protein of Mr of 60,000 as estimated by SDS-PAGE and could catalyze the phosphorylation of the synthetic peptide S6-21, the histone H4, and myelin basic protein. Mild digestion of the inactive S6/H4 kinase with trypsin was necessary, but not sufficient, to activate the kinase fully

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Chu Kit Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 142-168). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.iv / Abbreviations --- p.v / Publications Based on Work in this thesis --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- G protein-coupled receptors --- p.1 / Chapter 1.1.1 --- Introduction --- p.1 / Chapter 1.1.2 --- Heterotrimeric G proteins --- p.3 / Chapter 1.1.3 --- Second messenger systems --- p.4 / Chapter 1.1.4 --- Mechanism of GPCR activation --- p.6 / Chapter 1.2 --- Prostacyclin and its receptors --- p.9 / Chapter 1.2.1 --- General properties of prostacyclin --- p.9 / Chapter 1.2.1.1 --- Synthesis of prostacyclin --- p.9 / Chapter 1.2.1.2 --- Prostacyclin analogues --- p.10 / Chapter 1.2.2 --- Characterization of IP-receptors --- p.12 / Chapter 1.2.2.1 --- Distribution of IP-receptors --- p.12 / Chapter 1.2.2.2 --- Cloning of IP-receptors --- p.14 / Chapter 1.2.2.3 --- Structure of IP-receptors --- p.15 / Chapter 1.2.3 --- Coupling of IP-receptors to G proteins --- p.16 / Chapter 1.2.3.1 --- Interaction with Gs --- p.16 / Chapter 1.2.3.2 --- Interaction with Gq --- p.17 / Chapter 1.2.3.3 --- Interaction with Gi --- p.18 / Chapter 1.2.3.4 --- Interaction with PPARs --- p.20 / Chapter 1.2.4 --- Role of prostacyclin in mitogenesis/anti-mitogenesis --- p.20 / Chapter 1.3 --- Signal transduction network of MAPK family --- p.27 / Chapter 1.3.1 --- MAPK modules in mammalian cells --- p.29 / Chapter 1.3.1.1 --- Extracellular regulated kinase (ERK) cascade --- p.30 / Chapter 1.3.1.2 --- Stress-activated protein kinase (JNK and p38) cascades --- p.33 / Chapter 1.3.2 --- Activation ofERKl/2 through GPCRs --- p.35 / Chapter Chapter 2 --- Materials and solutions --- p.53 / Chapter 2.1 --- Materials --- p.53 / Chapter 2.2 --- "Culture media, buffer and solutions" --- p.58 / Chapter 2.2.1 --- Culture media --- p.58 / Chapter 2.2.2 --- Buffers --- p.59 / Chapter 2.2.3 --- Solutions --- p.62 / Chapter Chapter 3 --- Methods --- p.65 / Chapter 3.1 --- Maintenance of cell lines --- p.65 / Chapter 3.1.1 --- Chinese Hamster ovary (CHO) cells --- p.65 / Chapter 3.1.2 --- Human neuroblastoma (SK-N-SH) cells --- p.66 / Chapter 3.1.3 --- Rat/mouse neuroblastoma/glioma hybrid (NG108-15) cells --- p.66 / Chapter 3.2 --- Transient transfection of mammalian cells --- p.67 / Chapter 3.3 --- Measurement of ERK activity --- p.68 / Chapter 3.3.1 --- PathDetect® Elkl trans-Reporting System --- p.68 / Chapter 3.3.1.1 --- Introduction --- p.68 / Chapter 3.3.1.2 --- β-galactosidase assay --- p.72 / Chapter 3.3.1.3 --- Transient transfection of cells --- p.72 / Chapter 3.3.1.4 --- Cell assay --- p.73 / Chapter 3.3.1.5 --- Luciferase assay --- p.74 / Chapter 3.3.1.6 --- Micro β-gal assay --- p.74 / Chapter 3.3.1.7 --- Data analysis --- p.75 / Chapter 3.3.2 --- Western Blotting --- p.79 / Chapter 3.3.2.1 --- Introduction --- p.79 / Chapter 3.3.2.2 --- Transient transfection of cells --- p.79 / Chapter 3.3.2.3 --- Cell assay --- p.79 / Chapter 3.3.2.4 --- Protein electrophoresis and transfer --- p.80 / Chapter 3.3.2.5 --- Immunodetection --- p.80 / Chapter 3.4.1 --- Measurement of adenylyl cyclase activity --- p.83 / Chapter 3.4.1 --- wyo-[3H]-inositol labelling method --- p.83 / Chapter 3.4.1.1 --- Preparation of columns --- p.83 / Chapter 3.4.1.2 --- Incubation of cells --- p.84 / Chapter 3.4.1.3 --- Measurement of [3H]-cyclic AMP production --- p.84 / Chapter 3.4.1.4 --- Data analysis --- p.85 / Chapter 3.5 --- Measurement of phospholipase C activity --- p.85 / Chapter 3.5.1 --- wyo-[3H]-inositol labelling method --- p.85 / Chapter 3.5.1.1 --- Preparation of columns --- p.86 / Chapter 3.5.1.2 --- Incubation of cells --- p.86 / Chapter 3.5.1.3 --- Measurement of [3H]-inositol phosphate production --- p.87 / Chapter 3.5.1.4 --- Data analysis --- p.88 / Chapter Chapter 4 --- Results --- p.89 / Chapter 4.1 --- Validation of PathDetect® Elkl Trans-Reporting System --- p.89 / Chapter 4.1.1 --- Introduction --- p.89 / Chapter 4.1.2 --- Internal control --- p.89 / Chapter 4.1.3 --- Response to cicaprost and ATP --- p.91 / Chapter 4.1.4 --- Normalisation of ERK1/2 activity with transfection efficiency --- p.92 / Chapter 4.1.5 --- Cicaprost response in CHO cells in the absence of mIP- receptor --- p.93 / Chapter 4.1.6 --- Normalised luciferase activity reflecting ERK1/2 activation --- p.93 / Chapter 4.1.7 --- Conclusion --- p.95 / Chapter 4.2 --- Characterization of IP-receptors --- p.101 / Chapter 4.2.1 --- IP-receptor activation of adenylyl cyclase and phospholipase C --- p.101 / Chapter 4.2.2 --- IP-receptor activation ofERKl/2 in mIP-CHO cells --- p.102 / Chapter 4.2.2.1 --- PathDetect System --- p.102 / Chapter 4.2.2.2 --- Western Blotting --- p.103 / Chapter 4.2.2.3 --- Conclusion --- p.104 / Chapter 4.2.3 --- Role of the Gs-mediated pathway in cicaprost-stimulated ERK1/2 activation --- p.104 / Chapter 4.2.3.1 --- Role of cyclic AMP --- p.105 / Chapter 4.2.3.2 --- Role of protein kinase A --- p.106 / Chapter 4.2.4 --- Role of the Gq-mediated pathway in cicaprost-stimulated ERK1/2 activation --- p.106 / Chapter 4.2.4.1 --- Role of IP3 --- p.107 / Chapter 4.2.4.2 --- Role of protein kinase C --- p.108 / Chapter 4.2.4.3 --- Conclusion --- p.108 / Chapter 4.2.5 --- IP-receptor activation of ERKl/2 in hIP-CHO cells --- p.109 / Chapter 4.2.5.1 --- Activation ofERKl/2 in hIP-CHO cells --- p.109 / Chapter 4.2.5.2 --- Role of the Gq-mediated pathway in cicaprost- stimulated ERK 1/2 activation --- p.110 / Chapter 4.2.5.3 --- Role of the Gs-mediated pathway in cicaprost- stimulated ERK 1/2 activation --- p.111 / Chapter 4.2.5.4 --- Conclusions --- p.113 / Chapter 4.2.6 --- IP-receptor activation of ERX1/2 in neuroblastoma cells --- p.114 / Chapter 4.2.6.1 --- Rat/mouse neuroblastoma/glioma (NG108-15) cells --- p.114 / Chapter 4.2.6.2 --- Human neuroblastoma (SK-N-SH) cells --- p.115 / Chapter Chapter 5 --- General Discussion and Conclusions --- p.137 / References --- p.142

前體信使核糖核酸（pre‐mRNA）的剪接是在RNA成熟與蛋白質多樣性發生中所必需的一類高度動態的過程。作為一類特定的非小核糖核蛋白剪接因子，絲氨酸精氨酸（SR）蛋白在mRNA的組成型剪接及選擇性剪接，mRNA的轉運與翻譯中均扮演關鍵角色。SR蛋白在其氮端含有1個或2個RNA識別基序（RRMs），其碳端的RS結構域含有連續排列且可被高度磷酸化的精氨酸絲氨酸（RS）二肽。SR蛋白的磷酸化水平可調節其亞細胞定位與生理功能，而屬於蛋白激酶超家族的SR蛋白激酶（SRPK）家族負責SR蛋白的磷酸化修飾。 / 在此項課題中，我們著重於SRPK2獨特的底物特異性及其磷酸化機制的研究。課題選用兩個代表不同類型的底物：人類絲氨酸精氨酸剪接因子1（SRSF1）和人類細胞凋亡染色質聚縮引導因子S（acinusS）。研究結果顯示，氮端非激酶區為SRPK2對SRSF1和acinusS的激酶活力所必需。另外，雖然兩種底物類型一級結構迥異，但一個位於SRPK2的大葉且保守的docking groove，負責對它們的識別與結合。 / SRPK1以processive機制催化SRSF1中8‐10個位點，而我們的實驗結果顯示SRPK2以processive機制磷酸化SRSF1的約5‐6個位點。我們證明，SRPK2的docking groove對processive機制的磷酸化有著重要作用，而且位於dockinggroove中的組氨酸601決定了SRPK2較低的processvity。有趣的是，SRPK2的docking groove也在acinusS絲氨酸422的位點特異性磷酸化中起關鍵作用。我們證明該位點特異的磷酸化機制主要是由SRPK2的docking groove與位於acinusS磷酸化位點氮端推定的docking motif之間的離子型相互作用，及其隨之與一個同樣位於acinusS的磷酸化位點N端負的電荷區域之間的離子型排斥作用所調節。 / 這些結果顯示，SRPK2的docking groove採取了兩種不同的磷酸化機制，因而其底物可以或者processive機制，或者高度位點特異的機制被磷酸化修飾。此外，為闡明此兩種迥異的磷酸化機制的分子基礎，蛋白質晶體學研究正在進行之中。 / Pre‐mRNA splicing is a highly dynamic process that plays an essential role in mRNA maturation and protein diversity generation. One particular family of non‐small nuclear ribonucleoproteins (snRNPs) splicing factors, the serinearginine (SR) proteins, play critical roles in both constitutive and alternative mRNA splicing, mRNA transport, and translation. N‐terminus of SR proteins consists one or two RNA recognition motifs (RRMs), and the C‐terminal RS domain contains continuous RS dipeptides that could be extensively phosphorylated. The phosphorylation states of SR proteins regulate their subcellular localization and physiological functions. SR protein kinase (SRPK) family is a member of the kinase superfamily that accounts for SR protein phosphorylation. / In this study, we focused on the distinct substrate specificity and phosphorylation mechanism of SRPK2. Two substrates representing different classes are selected: human serine/arginine splicing factor 1 (SRSF1) and human apoptotic chromatin condensation inducer in the nucleus S (acinusS). Our results showed that the N‐terminal non‐kinase region of SRPK2 is required for the full catalytic activity towards both SRSF1 and acinusS. Besides, a conserved docking groove in the large lobe of SRPK2 was shown responsible for the recognition and binding of both substrate classes despite the significant difference in their primary structures. / While SRPK1 modifies SRSF1 for 8‐10 sites in a processive manner, our results show that SRPK2 processively phosphorylates SRSF1 for approximately 5‐6 sites. We provided evidence that the docking groove of SRPK2 is important for the processive phosphorylation mechanism and His601 within the groove accounts for the lower processivity. Interestingly, the docking groove also plays a critical role in the site‐specific phosphorylation of acinusS at Ser422. We demonstrated that the single site phosphorylation mechanism of SRPK2 is mainly regulated by ionic interaction with a putative docking motif, and the following ionic repulsion between the docking groove and an electronegative region N‐terminal to the P‐site of acinusS. / These results suggest that the docking groove of SRPK2 adopts two distinct phosphorylation mechanisms so that different RS domains can be phosphorylated in either processive or highly site‐specific manner. Protein crystallography studies are undergoing to provide the molecular basis of the two distinct phosphorylation mechanisms. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Liang, Ning. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 151-170). / Abstracts also in Chinese.

Development in shiitake mushroom, Lentinula edodes, is a unique process and studies of the molecular basis of this process may lead to improvement in mushroom cultivation. Previous studies have identified a number of signal transduction genes related to mushroom development, but those genes have not been well characterized. The present work characterized a developmentally regulated MAP kinase, Le.MAPK, Histidine kinase Le.nik1 and their interacting partners in the signal transduction pathways. / Histidine kinase Le.nik1 is the first Histidine kinase gene found in basidiomyces by differential display by RAP-PCR and it has a high sequence homology with the Histidine kinase from C. albicans and B. cinerea, which may be related to development and stress responses. A 7.8kb genomic DNA sequence and the full-length ORF of 6.29kb cDNA sequence of the two-component histidine kinase Le.nik1 has been determined. Northern blot analysis and real time RT-PCR showed that the transcript expression level of Le.nik1 increases from mycelium to mature fruiting body. This suggests that Le.nik1 plays an essential role in fruiting body development. In situ hybridization of different fruiting body stage demonstrated the transcript localization of Le.nik1 in the developing hymenophore and trama cells, which reveals Le.nik1's role in fruiting body development. Real time RT-PCR results suggest the relationship between Le.nik1 and dicarboximide fungicides and oxidant. Yeast two-hybrid studies of Le.nik1 response regulator yields two novel interacting protein and they may also be related to fruit body development as shown by real-time RT-PCR and in situ hybridization. / Le.MAPK gene was isolated and identified by RNA fingerprinting of differentially expressed genes. Le. MAPK shows high sequence identity to the MAP kinase in other fungus includes U. maydis, N. crassa and S. cerevisiae. Le.MAPK was found to be interacting with Le.DRMIP from the yeast two hybrid analyses. Le.DRMIP is a novel gene with a predicted N-terminal mitochondrial signal peptide, suggesting that their interactions relate to the mitochondrial signaling pathway. The expression profiles of these two genes reveal their importance in fruiting body initiation and development; the Le.DRMIP transcript is localized predominantly in the developing young fruit body and gills, which further signifies its role in cell differentiation during mushroom development. These results suggest a model in which Le.MAPK and Le.DRMIP regulate mitochondrial signal transduction during fruit body development in L. edodes. / Through the studies of Le. MAPK and Le.nik1 , this work enhances our knowledge of the role and functions of these signal transduction genes in mushroom development. These studies can also help us to investigate the biological function of these signal transduction genes in fungi and other organisms. / Szeto Ying Ying. / "October 2006." / Adviser: Hoi Shan Kwan. / Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 5750. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 126-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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The implication of the transmembrane signalling Receptor Tyrosine Kinases (RTKs) in cancer has accelerated the pursuit for drugs to target these molecules. In the process our understanding of how these membrane bound molecules are entangled in cell signalling has significantly expanded. There is now evidence that RTKs can facilitate the formation of a lattice-type network of signalling molecules to elicit whole cell responses to external ligand stimuli. Although beginning to be unravelled, knowledge pertaining to the mechanisms of molecular control that initiate these signalling pathways is still in its infancy. In this thesis, a random mutagenesis approach allowed the identification of the crucial interaction surfaces between membrane-bound EphA3 and its preferential binding partner ephrinA5, that are required to induce the formation of higher-order Eph signalling complexes. Modelling and experimental dissection of this co-ordinated receptor aggregation has provided detailed insights into the molecular mechanisms of Eph receptor activation, which in some aspects may also apply to other members of the RTK family. In particular, the importance of certain molecular interfaces in determining preferential and non-preferential Eph/ephrin interactions, suggests their role in the selection of biologically important binding partners. In addition to the assignment of the ephrin-interaction surfaces, the random mutagenesis strategy also identified a continuous conformational epitope as binding site for an anti-EphA3 monoclonal antibody. Fortuitously, antibody binding to this site functionally mimics ephrin stimulation of EphA3 positive cells, and in particular together with divalent ephrinA5, yields synergistically enhanced EphA3 activation. Elucidation of the underlying mechanism has provided opportunities to develop an efficient EphA3 targeting mechanism that is based on increased affinity and accelerated ephrinA5 uptake as consequence of this unique activation mechanism. On a genetic level, novel oligonucleotide analogues known as Peptide Nucleic Acids (PNAs) were analysed for their ability to sterically inhibit EphA3 DNA transcription and suggest a dosedependent downregulation of EphA3 expression, in malignant melanoma cells. Combined, ephrinA5, the anti-EphA3 MAb (IIIA4) and PNA, offer the possibility to investigate the specific machinery involved in Eph receptor expression and signalling for the specific targeting of EphA3 expressing tumour cells.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

This dissertation describes the cloning and characterization of the TOUSLEDlike kinases genes of maize (ZmTLKs). The TOUSLED-like kinases (TLKs) are a conserved family of nuclear Ser/Thr kinases in higher eukaryotes. The maize genome has three TOUSLED-like kinase genes (ZmTLK1, ZmTLK2, and ZmTLK3). Based upon sequence similarity, the ZmTLKs are divided into two classes, the ZmTLK1 and the ZmTLK2/3 class. The origins of these genes can be inferred from their map positions and relationships with TLKs in other Zea species. The ZmTLK1 and ZmTLK2 genes occupy syntenous positions on chromosome arms 1L and 5S in the maize genome. There are two equivalent classes of TLK genes in other Zea species, altogether indicating that the two ZmTLK classes are orthologous genes from the precursor species of maize, an ancient allotetraploid. Gene expression studies of ZmTLKs show that there is a higher level of expression in tissues undergoing DNA synthesis. This is consistent with studies of TLKs in animal systems that show involvement in chromatin assembly/remodeling activities during DNA replication and repair, as well as in transcription. The highest level of gene expression for the ZmTLK2/3 class was observed during development of the endosperm, in a period of massive nuclear endoreduplication. ZmTLK1 is not upregulated in endoreduplicating endosperm, suggesting functional divergence between the two classes of ZmTLK genes. The function of the ZmTLKs was examined by testing whether maize TLK genes could complement the tousled mutant of Arabidopsis. In Arabidopsis thaliana, recessive mutations in the single copy TOUSLED (TSL) gene cause moderate vegetative and severe floral defects, suggesting that TLKs may play a role in gene expression modulation through chromatin remodeling. The ZmTLK proteins are 84% identical to TSL in the catalytic region and 45 - 49% at the N-terminal regulatory domain. However, structural features of the N-terminal region domains of the ZmTLKs are similar to that of TSL. Arabidopsis tsl-1 mutant plants were transformed with ZmTLK2, under the control of the CaMV 35S promoter. These plants showed wild-type Arabidopsis phenotype, indicating that in spite of their sequence differences, ZmTLK2 and TSL interact with the same substrates and regulatory partners and are functionally equivalent. / Graduation date: 2005