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Few weeks after birth, a switch in peptide elongation factor 1As from EF-1alpha/EF1A-1 to S1/EF1A-2 occurs in brain neurons, heart and skeletal muscles of mammalians. In order to elucidate the reason behind this switch, I studied the expression of both homologous proteins during muscle differentiation and apoptosis and, documented the relation between peptide elongation factors and caspase-3 activation. I found that during in vitro muscle differentiation of L6 myoblasts, a switch in peptide elongation factors 1A occurs as physiologically observed in skeletal muscles. While EF-1alpha/EF1A-1 is expressed in replicating myoblasts, S1/EF1A-2 is solely found in differentiated myotubes where it replaces EF-1alpha/EFIA-1 as the major elongation factor. Similarly, upon serum deprivation-induced apoptosis, a reversion in peptide elongation factors 1A is observed: EF-1alpha/EF1A-1 replaces S1/EF1A-2 and becomes the major form of elongation factor 1A present in dying myotubes. This switch correlates in myotubes with the activation of caspase-3 protein, a cysteine protease involved in apoptosis. When L6 myotubes constitutively express S1/EF1A-2 as caused by adenoviral gene transfer, they become resistant to serum deprivation-induced apoptosis. In contrast, when L6 myotubes are transfected with EF-1alpha/EF1A-1 gene, they die more rapidly from serum deprivation-induced apoptosis than control cells. Transfection using anti-sense EF-1alpha/EF1A-1 gene protects myotubes from apoptotic cell death. Thus, both elongation factor 1As exert opposing effect on muscle survival: while EF-1alpha/EF1A-1 accelerates apoptotic cell death, S1/EF1A-2 protects muscles against apoptosis. / I found that skeletal muscles are the only tissues where, despite the constitutive expression of caspase-3 mRNA, the protein can be absent. Furthermore, I found that while immediately after birth, caspase-3 protein is present in skeletal muscles, a few weeks afterwards, the protein cannot be detected by Western blotting. In skeletal muscle, this change correlates with the observed switch in peptide elongation factors from EF-1alpha/EF1A-1 to S1/EF1A-2 and suggests that caspase-3 is translationally regulated in skeletal muscles. The laboratory previously reported that while EF-1alpha/EF1A-1 protein reappears; S1/EF1A-2 protein becomes absent from regenerating muscles. However, once tissue regeneration is completed, the situation returns to normal as EF-1alpha/EF1A-1 disappears and S1/EF1A-2 reappears to become the only type 1A elongation factor expressed in muscle. / In conclusion, I found that the developmental switch observed in peptide elongation factors from EF-1alpha/EF1A-1 to S1/EF1A-2 partly serves to protect muscle cells from apoptosis. Thus, I am the first to identify a noncanonical function for S1/EF1A-2. (Abstract shortened by UMI.)

Chu Lai On. / Thesis submitted in: July 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 152-172). / Abstracts in English and Chinese. / Acknowledgements --- p.2 / Abstract --- p.3 / Table of Content --- p.7 / Abbreviations --- p.12 / Naming system for mutant proteins --- p.13 / Abbreviations for amino acid --- p.14 / Chapter Chapter 1 --- Introduction --- p.15 / Chapter 1.1 --- Structure-function relationship of trichosanthin --- p.18 / Chapter 1.2 --- Properties of acidic ribosomal P-proteins --- p.21 / Chapter 1.3 --- Interaction among P-proteins and trichosanthin --- p.25 / Chapter 1.4 --- Properties of eukaryotic elongation factor 2 and interaction with P-proteins --- p.26 / Chapter 1.5 --- "Objectives and strategy of studying the interaction among trichosanthin, P-proteins and eukaryotic elongation 2" --- p.30 / Chapter Chapter 2 --- Materials and Methods --- p.33 / Chapter 2.1 --- General techniques --- p.33 / Chapter 2.1.1 --- Preparation and transformation of Escherichia coli competent cells --- p.33 / Chapter 2.1.2 --- Minipreparation of plasmid DNA using Wizard Plus SV Minipreps DNA purification kit from Promega --- p.34 / Chapter 2.1.3 --- Agarose gel electrophoresis of DNA --- p.36 / Chapter 2.1.4 --- Purification of DNA from agarose gel using Wizard SV Gel and PCR Clean-Up System from Promega --- p.36 / Chapter 2.1.5 --- Polymerase Chain Reaction (PCR) --- p.37 / Chapter 2.1.5.1 --- Basic Protocol --- p.37 / Chapter 2.1.5.2 --- Generation of P2 truncation mutants --- p.38 / Chapter 2.1.5.3 --- Generation of TCS mutants --- p.39 / Chapter 2.1.6 --- Restriction digestion of DNA --- p.41 / Chapter 2.1.7 --- Ligation of DNA fragments --- p.41 / Chapter 2.1.8 --- SDS-polyacrylamide gel electrophoresis (SDS-PAGE) --- p.42 / Chapter 2.1.9 --- Staining of protein in polyacrylamide gel --- p.45 / Chapter 2.2 --- Expression and purification of recombinant proteins --- p.46 / Chapter 2.2.1 --- "Bacterial culture, harvesting and lysis" --- p.46 / Chapter 2.2.2 --- Purification of recombinant TCS and mutants --- p.47 / Chapter 2.2.3 --- Purification of acidic ribosomal protein P2 and mutants --- p.48 / Chapter 2.2.4 --- Purification of MBP-fusion proteins --- p.50 / Chapter 2.3 --- Purification of eEF2 from rat livers --- p.51 / Chapter 2.4 --- In vitro binding assay by NHS-activated Sepharose resin --- p.53 / Chapter 2.4.1 --- Coupling of protein sample to NHS-activated Sepharose resin --- p.53 / Chapter 2.4.2 --- In vitro binding of protein sample to coupled NHS-activated resin --- p.54 / Chapter 2.5 --- Ribosome-inactivated activity assay using rabbit reticulocyte lysate in vitro translation system --- p.55 / Chapter 2.6 --- Circular dichroism (CD)spectrometry --- p.57 / Chapter 2.7 --- Isothermal titration calorimetry (ITC) experiment --- p.57 / Chapter 2.8 --- Surface plasmon resonance (SPR) experiment --- p.58 / Chapter 2.8.1 --- Immobilization of P2 onto aminosilane cuvette --- p.58 / Chapter 2.8.2 --- Interaction between eEF2 and immobilized P2 --- p.60 / Chapter 2.9 --- Preparation of Anti-P antibody --- p.61 / Chapter 2.10 --- Western blotting of protein --- p.62 / Chapter 2.11 --- Reagents and buffer --- p.64 / Chapter 2.11.1 --- Reagents for competent cell preparation --- p.64 / Chapter 2.11.2 --- Nucleic acids electrophoresis buffer --- p.65 / Chapter 2.11.3 --- Media for bacterial culture --- p.66 / Chapter 2.11.4 --- Buffers for TCS purification --- p.67 / Chapter 2.11.5 --- Buffers for eEF2 purification --- p.68 / Chapter 2.11.6 --- Reagents for SDS-PAGE --- p.68 / Chapter 2.11.7 --- Reagents and buffers for Western blot --- p.70 / Chapter 2.11.8 --- Reagents and buffers for coupling sample proteins to NHS-activated Sepharose resin --- p.72 / Chapter 2.11.9 --- Reagents and buffers for in vitro binding assay --- p.72 / Chapter 2.11.10 --- Reagents and Buffers for surface plasmon resonance --- p.72 / Chapter 2.12 --- Sequences of primers --- p.73 / Chapter Chapter 3 --- Interaction between TCS and P2 --- p.80 / Chapter 3.1 --- Introduction --- p.80 / Chapter 3.2 --- Interaction between TCS and P-proteins in rat liver lysate --- p.83 / Chapter 3.3 --- Construction of TCS mutants --- p.85 / Chapter 3.4 --- Expression and purification of TCS mutants --- p.87 / Chapter 3.5 --- Biological assay of TCS mutants --- p.91 / Chapter 3.6 --- Physical interaction of TCS mutants and P2 by surface plasmon resonance (SPR) --- p.94 / Chapter 3.7 --- Discussion --- p.100 / Chapter Chapter 4 --- Mapping the region of P2 that binds TCS and eEF2 --- p.104 / Chapter 4.1 --- Introduction --- p.104 / Chapter 4.2 --- Construction of P2 truncation mutants --- p.106 / Chapter 4.3 --- Expression and purification of P2 truncation mutants --- p.107 / Chapter 4.4 --- Mapping the region of P2 that binds TCS --- p.111 / Chapter 4.4.1 --- Interaction between TCS and P2 mutants by in vitro binding assay --- p.111 / Chapter 4.4.2 --- Interaction study of TCS and P2 mutant by isothermal titration calorimetry (ITC) --- p.116 / Chapter 4.5 --- Mapping the region of P2 that binds eEF2 --- p.120 / Chapter 4.5.1 --- Purification of eEF2 from rat liver --- p.120 / Chapter 4.5.2 --- Physical interaction of P2 and eEF2 by surface plasmon resonance (SPR) --- p.126 / Chapter 4.5.3 --- Interaction between eEF2 and P2 mutants by in vitro binding assay --- p.128 / Chapter 4.6 --- Mapping the C-terminal region of P2 by MBP-fusion proteins --- p.130 / Chapter 4.6.1 --- Construction and purification of MBP-fusion proteins --- p.131 / Chapter 4.6.2 --- "Interaction among eEF2, TCS and MBP-fusion proteins by in vitro binding assay" --- p.133 / Chapter 4.7 --- Discussion --- p.137 / Chapter Chapter 5 --- Effect of C-17 peptide on TCS biological activity --- p.143 / Chapter 5.1 --- Introduction --- p.143 / Chapter 5.2 --- Ribosome-inactivating activity of TCS with C-17 peptide --- p.145 / Chapter 5.3 --- Discussion --- p.147 / Chapter Chapter 6 --- Conclusion and suggestions for future study --- p.149 / References --- p.152 / Appendix --- p.173