Biomolecular action of ionizing radiation /

Table Of Contents:
Acknowledgments xxv
Abbreviations xxvii
Chapter 1 Introduction 1

References 4
Chapter 2 Basic Radiation Physics and Chemistry 5

2.1 Ionization and Excitation 5

2.2 Types of Ionizing Radiation 5

2.2.1 Electromagnetic Radiation 5

2.2.2 Particulate Radiations 7

2.3 Processes of Energy Absorption 8

2.4 Direct and Indirect Action of Radiation 10

2.5 Radiolysis of Water 12

2.5.1 Haber鈥擶eiss Reaction 14

2.5.2 Reactions of the Primary Radiolytic Products of Water with Target Molecules 14

2.5.2.1 Hydrogen Abstraction 15

2.5.2.2 Dissociation 15

2.5.2.3 Addition Reactions 15

2.5.3 Solute Radicals Form Stable Products 15

2.6 Linear Energy Transfer 16

2.7 Relative Biological Efficiency 18

2.8 Summary 19

Reference 19

Bibliography 19
Chapter 3 Basic Cell Biology and Molecular Genetics 21

3.1 Basic Cell Biology 21

3.1.1 Cell Membrane 21

3.1.2 Cytoplasm 24

3.1.3 Nucleus 24

3.1.4 Mitochondria 25

3.1.4.1 Mitochondrial Structure 25

3.1.4.2 Mitochondrial Function 26

3.1.5 Endoplasmic Reticulum and Ribosomes 27

3.1.6 Golgi Complex 27

3.1.7 Cytoskeleton 28

3.1.7.1 Centrosome and Centrioles 28

3.1.8 Lysosomes 29

3.1.9 Extracellular Materials 29

3.1.10 Summary: Cell Biology 29

3.2 Molecular Genetics 29

3.2.1 DNA Structure 30

3.2.2 DNA Structure Is the Basis for Heredity 32

3.2.3 Mechanism of DNA Replication 34

3.2.3.1 DNA Replication Fork 34

3.2.3.2 Proofreading Mechanisms 35

3.2.3.3 Proteins Involved in DNA Replication 36

3.2.4 Transcribing DNA to RNA 37

3.2.4.1 One DNA Strand Is Transcribed into RNA 38

3.2.4.2 RNA and RNA Polymerases 39

3.2.4.3 Transcription Stop Signals 39

3.2.4.4 General Transcription Factors 40

3.2.4.5 Processing the mRNA Molecule 41

3.2.5 From RNA to Protein 42

3.2.5.1 Decoding mRNA 42

3.2.5.2 RNA Message Is Decoded on Ribosomes 44

3.2.5.3 Regulation of Gene Expression 45

3.2.6 Proteins 47

3.2.7 Summary: Molecular Genetics 48

Bibliography 50
Chapter 4 Methods of Cell and Molecular Radiobiology 51

4.1 Methods of Classical Radiobiology 51

4.1.1 Cell Survival In Vitro: The Clonogenic Assay 51

4.1.1.1 Colony Formation as an Index of Survival 51

4.1.1.2 Clonogenic Assay: Procedure 51

4.1.1.3 Clonogenic Assay: Results 52

4.1.1.4 Clonogenic Assay Adapted for Study of Response to Low Doses 55

4.1.2 Non-Clonogenic Assays 55

4.1.3 Methods of Cell Synchronization 56

4.1.3.1 Synchrony by Release from Go Arrest 56

4.1.3.2 Synchrony by Release from M-Phase Block 56

4.1.3.3 Synchrony by Release from S-Phase Block 56

4.1.3.4 Synchrony by Mitotic Detachment 57

4.1.3.5 Synchrony by Centrifugal Elutriation 57

4.1.4 Determination of Duration of Phases of the Cell Cycle 58

4.1.4.1 Microscopy 58

4.1.4.2 Flow Cytometry 59

4.1.5 Measuring Cell Survival In Vivo 62

4.1.5.1 Transplantable Solid 'Tumors in Experimental Animals 62

4.1.5.2 Assays of Radiation-Dose Relationships for Cells from Normal Tissues 64

4.2 Methods for Detecting Damage to DNA 65

4.2.1 Strand Break Assays 67

4.2.1.1 Sucrose Gradient Centrifugation 67

4.2.1.2 Filter Elution 67

4.2.1.3 Electrophoretic Methods 67

4.2.1.4 Nucleoid Assays 68

4.2.2 Measurement of DNA Damage and Repair in Individual Mammalian Cells 69

4.2.2.1 Single-Cell Gel Electrophoresis or Comet Assay 69

4.2.2.2 Micronucleus Test 70

4.2.2.3 Chromosome Aberrations, Premature Chromosome Condensation, and Fluorescent In Situ Hybridization 71

4.2.2.4 Measurement of the Fidelity of Rejoining 71

4.2.3 Summary 72

4.3 Tools and Techniques of Molecular Biology 72

4.3.1 Hybridization of Nucleic Acids 72

4.3.2 Restriction Enzymes 74

4.3.3 Gel Electrophoresis and Blotting Techniques 74

4.3.3.1 Southern and Northern Blotting 75

4.3.4 Polymerase Chain Reaction 76

4.3.4.1 Quantitative Real-Time Polymerase Chain Reaction 78

4.3.5 Putting New Genes into Cells: DNA-Mediated Gene Transfer 79

4.3.6 Generation of a Cloned Probe or DNA Library 80

4.3.7 Sequencing of DNA 83

4.3.8 Single Nucleotide Polymorphisms 84

4.3.9 Functional Inactivation of Genes 84

4.3.9.1 Site-Directed Mutagenesis 84

4.3.9.2 Antisense Oligonucleotides 85

4.3.9.3 siRNA 85

4.3.9.4 Transgenic and Knockout Mice 86

4.3.10 Genomic Methods of Tumor Analysis 87

4.3.10.1 Fluorescence In Situ Hybridization 87

4.3.10.2 Spectral Karyotyping and Multi-Fluor Fluorescence In Situ Hybridization 87

4.3.10.3 Microarray Analysis of Genes 88

4.3.11 Analysis of Proteins 89

4.3.11.1 Western Blotting 89

4.3.11.2 Two-Dimensional Electrophoresis 90

4.3.11.3 Immunoprecipitation 90

4.3.11.4 Enzyme-Linked Immune-Absorbant Assay 90

4.3.11.5 Far Western Blotting 91

4.3.11.6 Fluorescent Proteins 91

4.3.12 Production of Monoclonal Antibodies 91

4.3.13 Proteomics: Analysis of Protein Structure and Function 92

4.3.14 Analysis of Tissue Sections and Single Cells 93

4.3.15 Laser Capture Microdissection 93

References 93
Chapter 5 Ionizing Radiation Effects to the Cytoplasm 97

5.1 Oxidative Stress 97

5.1.1 Metabolic Oxidative Stress 98

5.1.1.1 Important ROS/RNS 99

5.1.1.2 Cellular Antioxidant Enzymes 102

5.1.1.3 Low Molecular Weight Antioxidant Compounds and Thioredoxin 105

5.2 Ionizing Radiation-Induced ROS/RNS 105

5.2.1 Demonstration of Radiation-Induced Intracellular ROS/RNS 105

5.2.2 Mechanisms of Generation and Amplification of ROS/RNS Following Irradiation of the Cytoplasm 107

5.2.2.1 Increase of Pentose Cycle Activity 107

5.2.2.2 Role of NADPH Oxidase 108

5.2.2.3 Mitochondrial Permeability and ROS/RNS Generation 108

5.2.2.4 Nitric Oxide Synthase and Nitric Oxide 109

5.2.3 Consequences of Radiation-Induced Generation of ROS/RNS 110

5.2.3.1 Signal Transduction and Transcription Factor Activation 110

5.2.3.2 Mutagenic and Clastogenic Effects 111

5.2.3.3 Bystander Effects 112

5.3 Effects of Ionizing Radiation on the Cell Membrane 112

5.3.1 Structure of the Cell Membrane 113

5.3.2 Lipid Peroxidation in Plasma Membranes 114

5.3.3 Consequences of Damage to Plasma Membrane Lipids 115

5.3.4 Plasma Membrane Is a Target for Ionizing Radiation-Induced Apoptosis 116

5.4 Summary 117

References 118
Chapter 6 Damage to DNA by Ionizing Radiation 121

6.1 Mechanisms of DNA Damage: Physicochemical Relationships 121

6.1.1 Mechanisms of Damage Induction: Chemical End Points 122

6.1.2 Mechanisms of Damage Induction: Cellular End Points 123

6.2 Types of DNA Damage 124

6.2.1 Simple Damages to DNA: Base Damage and Single-Strand Breaks 124

6.2.2 Apurinic or Apyrimidinic Sites 128

6.2.3 Modifiers of Radiation Effect 129

6.2.4 DNA Strand Breaks 130

6.3 Double-Strand Breaks and Other Multiply Damaged Sites 132

6.3.1 Distribution of MDS 133

6.3.2 Clustered Damage in DNA of Mammalian Cells 134

6.4 DNA-Protein Cross-Links 135

6.5 Summary 135

References 137
Chapter 7 Repair of Radiation Damage to DNA 141

7.1 Overview of DNA Repair Mechanisms 141

7.2 Repair of Radiation-Induced DNA Damage 143

7.2.1 Repair of Base Damage and Single-Strand DNA Breaks: Base Excision Repair 143

7.2.2 Role of PARP 146

7.2.3 Processing of Multiply Damaged Sites by BER 148

7.3 Repair of DNA Double-Strand Breaks 150

7.3.1 Homologous Recombination 151

7.3.1.1 Role of BRCA1 and BRCA2 153

7.3.1.2 Single-Strand Annealing 154

7.3.1.3 Role of Homologous Recombination in DNA Repair in Mammalian Cells 154

7.3.2 Nonhomologous End Joining 155

7.3.2.1 Demonstration of NHEJ in Mammalian Cells Using Repair-Deficient Mutants 155

7.3.3 Genes and Proteins Involved in NHEJ 157

7.3.3.1 DNA-PK 157

7.3.3.2 Ku Proteins 158

7.3.3.3 DNA-PKcs 159

7.3.3.4 XRCC4 Gene Product 159

7.3.3.5 NHEJ and Severe Combined Immunodeficiency 160

7.3.3.6 Role of NHEJ Proteins in V(D)J Recombination 160

7.3.3.7 Artemis 161

7.3.3.8 Nuclear Foci: Mre11-Rad 50-Nbs1 and Others 162

7.3.3.9 Mechanism of NHEJ 163

7.3.3.10 An Alternative, Microhomology-Dependent NHEJ Pathway 165

7.3.4 Telomere-Bound Proteins and DNA Repair 166

7.4 Human Syndromes Involving DNA Repair Deficiency 167

7.5 Relationship between DNA Repair and Cell Survival 168

7.6 Summary 169

References 171
Chapter 8 Cellular Response to DNA Damage 175

8.1 Passing on the Message that DNA Has Been Damaged 175

8.1.1 Signal Transduction 176

8.1.2 Signal-Transduction Cascade Initiated by Radiation-Induced DNA Damage 177

8.2 ATM Protein 177

8.2.1 Functions of ATM 178

8.2.2 How Does ATM Respond to Radiation-Induced DNA Damage? 180

8.2.3 Role of ATM in DNA Repair 181

8.2.4 ATM and the MRN Complex 182

8.3 Tumor Suppressor Gene p53 183

8.3.1 Turnover of p53: Mdm2 186

8.3.1.1 Protein Degradation by the Ubiquitin-Proteasome System 186

8.3.2 Modulation of p53 Stability and Activity 188

8.3.2.1 Bypassing Mdm2 188

8.3.2.2 Localization of p53 189

8.3.2.3 Post-Translational Modification 189

8.4 Radiation-Induced Growth Arrest 190

8.4.1 Cell Cycle: Cyclins and Cyclin Dependent Kinases 190

8.4.2 Radiation-Induced Cell-Cycle Arrest 193

8.4.2.1 G1 Arrest 194

8.4.2.2 S-Phase Checkpoint 194

8.4.2.3 G2/M Arrest 196

8.4.2.4 Modifying the G2/M Delay: Caffeine and Related Drugs 196

8.4.3 Oncogenes and Cell-Cycle Checkpoints 197

8.4.4 Variation in Radiosensitivity through the Cell Cycle 198

8.5 p53-Mediated Apoptosis 199

8.6 Summary 200

References 202
Chapter 9 Chromatin Structure and Radiation Sensitivity 205

9.1 Cell Nucleus 205

9.1.1 Hierarchical Structure of Chromatin 205

9.1.2 Structure and Function: Chromatin and the Nuclear Matrix 207

9.2 Protection of DNA from Radiation Damage by Nuclear Proteins 208

9.2.1 DNA-Protein Cross-Link Formation 210

9.2.2 DSB Yields and RBE 210

9.2.3 Role of Polyamines 211

9.3 Radiation Sensitivity and the Stability of the DNA鈥揘uclear Matrix 211

9.4 Radiosensitivity of Condensed Chromatin 213

9.5 Role of Chromatin in DNA DSB Recognition and Repair 215

9.5.1 Histone 2AX 215

9.5.2 ATM Signaling from Chromatin 217

9.5.3 Modulation of Chromatin Structure and Function by Acetylation 217

9.5.4 Radiosensitization by Histone Deacetylase Inhibitors 218

9.6 Summary 219

References 220
Chapter 10 Radiation-Induced Chromosome Damage 223

10.1 DNA, Chromosomes, and the Cell Cycle 223

10.1.1 Organization of DNA into Chromatin and Chromosomes 223

10.1.2 Cell Cycle 223

10.1.3 Mitosis 225

10.2 Radiation-Induced Chromosome Aberrations 227

10.2.1 Nature of the Initial Lesion 228

10.2.2 Partial Catalog of Chromosome and Chromatid Aberrations 229

10.2.2.1 Chromosome Aberrations Produced by Irradiation in G1 or Early S Phase 229

10.2.2.2 Chromatid Aberrations Produced in Mid to Late S and in G2 231

10.3 Visualization of Chromosome Breaks during Interphase: Premature Chromosome Condensation 232

10.3.1 FISH, mFISH, SKY, mBAND FISH, and Chromosome Painting 233

10.3.2 Results of Whole Chromosome Painting 234

10.4 Mechanisms of Aberration Formation 235

10.4.1 Chromosome Localization and Proximity Effects 237

10.5 Implications of Chromosome Damage 238

10.5.1 Genetics 238

10.5.2 Carcinogenesis 239

10.5.3 Cell Survival, Dose Rate, and Fractionation Response 240

10.5.4 Genomic Instability 243

10.5.5 Biodosimetry and Risk Estimation 244

10.6 Summary 245

References 246
Chapter 11 Modulation of Radiation Response via Signal Transduction Pathways 251

11.1 Intracellular Signaling 251

11.2 Transmembrane Receptors 251

11.2.1 ErbB Family of Receptor Kinases 253

11.2.2 Cytoplasmic Signaling 254

11.2.3 Ras Proto-Oncogene Family 254

11.2.4 Signal Transduction Cascades 255

11.2.4.1 MAPK Superfamily of Cascades 256

11.2.4.2 MAPK Pathway 258

11.2.4.3 c-JUN NH2 Terminal Kinase Pathway 258

11.2.4.4 p38 MAPK Pathway 259

11.2.4.5 Phosphatidyl Inositol 3-Kinase Pathway 259

11.3 Modulation of Radiation Response by Interaction of Signal Transduction Pathways 261

11.3.1 Activation of ErbB Receptors by Ionizing Radiation 261

11.3.2 Mechanism of Receptor Activation by Ionizing Radiation 261

11.3.3 Role of Other Growth Factors 261

11.3.4 Effects of Activation of GF Receptors on Cell Survival 262

11.3.4.1 Anti-Apoptotic Signaling 262

11.3.4.2 Cell-Cycle Regulation 263

11.3.5 Autocrine Signaling 265

11.4 Radiosensitization by Modulation of Signal Transduction Intermediates: Molecular Radiosensitizers 266

11.4.1 ErbB Family Signal Inhibitors 266

11.4.2 Clinical Applications of EGFR Signal Inhibitors 267

11.4.3 Inhibition of the Ras-Mediated Signaling Pathway 269

11.4.4 Clinical Application of Farnesyl Transferase Inhibitors 271

11.4.5 Clinical Implications of Radiation-Induced Cell Signaling: Accelerated Cell Proliferation 271

11.5 Summary 272

References 273
Chapter 12 Radiation-Induced Apoptosis 279

12.1 Apoptosis 279

12.2 Mechanisms of Apoptosis 279

12.2.1 Caspases 281

12.3 Apoptotic Signaling Pathways 282

12.3.1 Intrinsic Apoptotic Signaling: The Mitochondrial Pathway 282

12.3.1.1 Bcl-2 Proteins 283

12.3.1.2 Precipitating the Caspase Cascade 284

12.3.1.3 Activation of Mitochondrial Caspases by Inhibition of IAPs 286

12.3.1.4 p53-Regulated Apoptosis Initiated by DNA Damage 286

12.3.2 Extrinsic Apoptotic Signaling 287

12.3.2.1 Mechanism of Apoptosis Mediated through the Death Receptors 287

12.3.2.2 Fas-Mediated Cell Death Initiated by Damage to Genomic DNA 289

12.3.2.3 Therapeutic Application of Tumor Necrosis-Factor Related Apoptosis-Inducing Ligand for Radiosensitization 289

12.3.2.4 Suppression of Apoptosis by Anti-Apoptotic Signaling 290

12.3.3 Extrinsic Apoptotic Signaling Initiated at the Plasma Membrane: The Ceramide Pathway 291

12.3.3.1 Ceramide as a Second Messenger Regulating Stress Responses 291

12.3.3.2 Synthesis and Metabolism of Ceramide 293

12.3.3.3 Apoptotic Signaling via Ceramide 293

12.3.3.4 Ceramide-Mediated Apoptosis Induced by DNA Damage: Role of Ceramide Synthase 294

12.3.3.5 Ceramide Rafts 295

12.3.3.6 Upstream Pathways That Antagonize to Ceramide-Signaled Apoptosis 295

12.4 Why Do Some Cells Die as the Result of Apoptosis and Not Others? 296

12.5 Apoptotic Processes and the In Vivo Radiation Response 297

12.5.1 Normal Tissue 297

12.5.2 Tumor Response 299

12.5.2.1 Experimental Studies with Rodent Tumors 299

12.5.2.2 Human Tumor Systems 300

12.6 Summary 301

References 302
Chapter 13 Early and Late Responding Genes Induced by Ionizing Radiation 307

13.1 Gene Expression Is Induced by Ionizing Radiation 307

13.1.1 Transcription Factors 308

13.1.2 Important Transcription Factors Activated by Radiation 310

13.1.2.1 p53 310

13.1.2.2 Nuclear Factor Kappa B 311

13.1.2.3 Activating Protein-1 Transcription Factor 312

13.1.2.4 Early Growth Response Factor Egr-1 315

13.1.2.5 SP Family of Transcription Factors 316

13.1.3 Radiation Gene Therapy 316

13.1.3.1 Clinical Trials of Radiation-Targeted Gene Therapy 319

13.2 Early and Late Response Genes 320

13.2.1 Induction of Late Response Genes by Ionizing Radiation 320

13.2.1.1 Transforming Growth Factor-131 323

13.2.1.2 Platelet-Derived Growth Factor 323

13.2.1.3 Basic Fibroblast Growth Factor 323

13.2.1.4 Tumor Necrosis Factor a 323

13.2.1.5 Radiation-Inducible Interleukins 324

13.2.2 Cytokine-Mediated Responses in Irradiated Tissues 324

13.2.2.1 Brain 325

13.2.2.2 Lung 325

13.2.2.3 Intestine 326

13.2.3 Late Effects: Radiation-Mediated Fibrosis 327

13.2.4 Gene Expression Associated with Radiation-Mediated Vascular Damage 328

13.3 Cytokines as Therapeutic Agents: Radioprotection and Radiosensitization 328

13.3.1 Radiosensitization 328

13.3.2 Radioprotection 330

13.4 Radiation-Induced Genes and Gene-Products as Biomarkers of Radiation Exposure 330

13.5 Summary 331

References 333
Chapter 14 Cell Death, Cell Survival, and Adaptation 339

14.1 Cell Death 339

14.1.1 Modes of Cell Death in Nonirradiated Cells 339

14.1.1.1 Apoptosis 339

14.1.1.2 Senescence 340

14.1.1.3 Necrosis 340

14.1.1.4 Autophagy 340

14.1.1.5 Mitotic Catastrophe 340

14.1.2 Radiation-Induced Cell Death 341

14.1.2.1 Mechanisms of Cell Death in Normal Tissue 341

14.1.2.2 Cell Death in Tumors 342

14.1.3 Role of p53 344

14.2 Quantitating Cell Kill: Analysis of Cell-Survival Curves 345

14.2.1 Target Theory 345

14.2.2 Linear Quadratic Model 348

14.2.3 Lethal, Potentially Lethal Damage Model 349

14.2.4 Repair Saturation Models 349

14.3 Cell Survival at Low Radiation Doses 350

14.3.1 Low-Dose Hypersensitivity 350

14.3.1.1 HRS Requires a Threshold Level of DNA Damage 352

14.3.1.2 HRS and DNA Repair 352

14.3.1.3 HRR/IRS in Relation to the Cell Cycle 353

14.3.2 Adaptive Response 354

14.3.2.1 Time and Dose Relationships for the Adaptive Response 355

14.3.2.2 Mechanisms of the Adaptive Response 356

14.4 Interactions of Adaptive Response and Bystander Effects 357

14.5 Implications of Low-Dose Effects for Risk Assessment 359

14.5.1 Exposure to Background Radiation 359

14.5.2 Adaptive Response and Neoplastic Transformation 359

14.6 Clinical Implications of Low-Dose Effects 360

14.7 Summary 361

References 362
Chapter 15 Bystander Effects and Genomic Instability 367

15.1 Dogma of Radiation Biology 367

15.2 Bystander Effects 368

15.2.1 Bystander Effects In Vitro 369

15.2.1.1 Evidence for a Radiation-Induced Bystander Effect from Experiments Using Low Fluences of a Particles 369

15.2.1.2 Evidence for Bystander Effects after Radiation with Charged-Particle Microbeams 371

15.2.1.3 Irradiation of the Cytoplasm 372

15.2.1.4 Microbeams Targeted to the Nucleus 372

15.2.2 Bystander Effects Seen after Transfer of Medium from Irradiated Cells 375

15.2.2.1 Connection to Radiation Hypersensitivity 378

15.2.2.2 Bystander-Mediated Adaptive Response 378

15.2.2.3 Death-Inducing Effect 379

15.2.3 Bystander Effects In Vivo 381

15.2.3.1 Abscopal Effects of Radiation 382

15.2.3.2 Clastogenic Factors Induced by Ionizing Radiation 383

15.2.4 Mechanisms Underlying Radiation-Induced Bystander Effects 384

15.2.5 Implications in Risk Assessment 385

15.3 Genomic Instability 387

15.3.1 Genomic Instability In Vitro: Delayed Responses to Radiation Exposure 387

15.3.2 Demonstration of Genomic Instability In Vivo 389

15.3.3 Genomic Instability and Cancer 390

15.3.4 Mechanisms Underlying Radiation-Induced Genomic Instability 391

15.3.5 Relationship between Radiation-Induced Bystander Effects and Genomic Instability 392

15.4 Summary 393

References 395
Chapter 16 Tumor Radiobiology 399

16.1 Tumor Radiobiology 399

16.2 Unique Tumor Microenvironment 399

16.2.1 Interstitial Fluid Pressure 401

16.2.2 Tumor Hypoxia 401

16.2.3 Tumor Acidosis 402

16.2.4 Tumor Metabolism: Aerobic and Anaerobic Glycolysis 402

16.3 Tumor Microenvironment Creates Barriers to Conventional Therapies 405

16.3.1 Chemotherapy 405

16.3.2 Radiotherapy 406

16.3.2.1 Tumor Hypoxia and Radioresistance 406

16.3.2.2 Radiosensitization by Oxygen 406

16.3.2.3 Hypoxia in Tumors 408

16.3.2.4 Acute and Chronic Hypoxia 408

16.3.2.5 Re-Oxygenation 409

16.3.3 Measurement of Tumor Hypoxia 411

16.3.3.1 Experimental Tumors 411

16.3.3.2 Measurement of Hypoxia in Human Tumors 412

16.3.4 Radio-Sensitization by Modifying Tumor Oxygenation 415

16.3.4.1 Modification of Physiology and Metabolism 415

16.3.4.2 Drugs Targeting Hypoxic Cells 416

16.4 Effect of Hypoxia on Tumor Development and Progression 418

16.4.1 Regulation of Gene Expression by Hypoxia 418

16.4.2 Hypoxia-Induced Factor 1: Regulator of Oxygen Homeostasis 419

16.4.2.1 Oxygen-Dependent Regulation of HIF-1 419

16.4.2.2 Oxygen-Independent Regulation of HIF-1 420

16.4.3 Genes That Are Transcriptionally Activated by HIF-1 423

16.4.3.1 Metabolism 423

16.4.3.2 Apoptosis 423

16.4.3.3 Angiogenesis and Oxygen Delivery 424

16.4.3.4 Invasion and Metastasis 424

16.4.4 Endogenous Hypoxia Markers in Human Tumors 425

16.4.5 Therapeutics Based on Tumor-Specific Targeting 425

16.4.5.1 Targeting Cells Which Express HIF-1 426

16.4.6 HIF-1 and Radioresistance 427

16.5 Targeting the Ubiquitin/Proteasome System 427

16.6 Summary 428

References 430
Chapter 17 Radiation Biology of Nonmammalian Species: Three Eukaryotes and a Bacterium 435

17.1 Introduction: Lower Eukaryotes in Radiation Research 435

17.2 Yeast, a Single-Celled Eukaryote 436

17.2.1 Radiation Biology of Yeast 437

17.2.2 Radiosensitive Mutants for the Study of DNA Repair 438

17.2.3 DNA-Damage Checkpoints 441

17.2.4 Genome-Wide Screening for Radiation Response-Associated in Yeast 444

17.3 Caenorhabditis elegans 445

17.3.1 Apoptosis in C. elegans 446

17.3.1.1 Developmental Cell Death 446

17.3.1.2 C. elegans p53 Homologue CEP-1 447

17.3.1.3 Radiation-Induced Apoptosis 447

17.3.2 Cell Cycle Checkpoints in C. elegans 448

17.3.2.1 Radiosensitivity of Checkpoint Mutants 449

17.3.3 DNA Repair in C. elegans 450

17.3.3.1 Genes Involved in Meiotic DNA Recombination 450

17.3.4 DNA Damage Responses in C. elegans 450

17.3.4.1 Genes Protecting against Effects of Ionizing Radiation 451

17.3.5 Radiation-Induced Mutation 451

17.3.6 Worms in Space 453

17.4 Zebrafish 454

17.4.1 Zebrafish for the Evaluation of Genotoxic Stress 455

17.4.2 Effects of Ionizing Radiation on Brain and Eye Development 456

17.4.3 Modulation of Radiation Response 457

17.4.4 Gene Function during Embryonic Development 458

17.4.4.1 Expression of Zebrafish ATM 459

17.4.4.2 Ku80 459

17.4.5 Hematological Studies with Zebrafish 460

17.4.5.1 Hematopoietic Syndrome in Zebrafish 460

17.4.5.2 Hematopoietic Cell Transplantation in Zebrafish 461

17.5 Deinococcus radiodurans 461

17.5.1 Origins of Extremophiles 462

17.5.2 Genetics of D. radiodurans 463

17.5.3 Characteristics of D. radiodurans Predisposing to Radiation Resistance 463

17.5.3.1 Genome Copy Number 464

17.5.3.2 Nucleoid Organization 464

17.5.3.3 Manganese Content 464

17.5.4 Regulation of Cellular Responses to Extensive Radiation Damage 465

17.5.4.1 Radiation-Induced DNA Repair Genes 465

17.5.4.2 DNA End Protection 466

17.5.4.3 RecA-Independent Double-Strand Break Repair 466

17.5.4.4 Recombinational DNA Repair 468

17.5.5 Double-Strand Break Tolerance 468

17.5.6 An Economic Niche for D. radiodurans 469
References 469
Glossary 473
Index 509