ABOUT THIS BOOK"Gene sharing" means that the different functions of a protein may share the same gene--that is, a protein produced by a gene evolved to fulfill a specialized function for one biological role may also perform alternate functions for other biological roles.
In the 1980s and early 1990s, Joram Piatigorsky and colleagues coined the term "gene sharing" to describe the use of multifunctional proteins as crystallins in the eye lens. In Gene Sharing and Evolution Piatigorsky explores the generality and implications of gene sharing throughout evolution and argues that most if not all proteins perform a variety of functions in the same and in different species, and that this is a fundamental necessity for evolution.
How is a gene identified, by its structure or its function? Do the boundaries of a gene include its regulatory elements? What is the influence of gene expression on natural selection of protein functions, and how is variation in gene expression selected in evolution? These are neither new nor resolved questions. Piatigorsky shows us that the extensiveness of gene sharing and protein multifunctionality offers a way of responding to these questions that sheds light on the complex interrelationships among genes, proteins, and evolution.
REVIEWSEvery textbook of molecular evolution has a section on gene sharing but this is the first book entirely devoted to the topic. Piatigorsky considers almost all aspects of gene sharing, provides numerous examples, and discusses the importance and contribution of gene sharing to evolution. He argues forcefully that gene sharing is widespread in many genomes. His arguments will likely alter the prevailing view of gene sharing as a unique phenomenon to crystallins.
-- Jianzhi George Zhang, Associate Professor of Ecology and Evolutionary Biology at the University of Michigan
This book introduces, explains and elaborates on the very interesting fact that some genes produce proteins that serve different (and important) functions in the same organism. This is a remarkable story well told and interesting from both evolutionary and functional perspectives.
-- Russell D. Fernald, Benjamin Scott Crocker Professor of Biological Sciences at Stanford University
It has been a dogma of evolutionary biology that gene duplication precedes the evolution of new gene and protein function. Joram Piatigorsky stands this scenario on its head by showing that, in the case of lens crystallins and probably other protein families, functional diversity can precede gene duplication. His revolutionary perspective provides unexpected insight into how biological systems evolve.
-- Austin Hughes, Professor of Biological Sciences, University of South Carolina
I have not encountered such an interesting, intellectually stimulating and exciting biological monograph in many years. Piatigorsky discusses the phenomenon of gene sharing on all levels, the molecular and cellular, as well as in the context of ìsystem biologyî and finally its ramifications on our views on evolution. He manages to concentrate a tremendous amount of information in this book and whatever he says has experimental backing. His precise and detailed technical descriptions are presented in a very readable style that also projects a sense of wonder and surprise. This is an extraordinary book that I hope will have an important impact on future biological thinking.
-- Dr. Alex Keynan, Professor at Hebrew University and Special Adviser to the President of the Israeli National Academy of Sciences
[Gene Sharing and Evolution] provides great motivation for evolutionists to continue investigating the origins of new protein function, a topic central to evo-devo biology. The book is a parade of interesting molecular biology with abundant and clear color illustrations. The work is copiously referenced. With over 1100 references in the bibliography, most anyone is certain to find new and interesting literature. As such, I recommend Gene Sharing and Evolution for a graduate seminar, as a reference book on gene multi-functionality with many detailed examples, and for anyone pondering the evolutionary origins of novelty at the molecular level.
-- Todd H. Oakley Evolution & Development
A masterpiece for a broad medical and scientific readership. The text provides a powerful reminder that genes and proteins do not function as isolated entities but are components of a dynamic and elaborate temporal network. With the recent advent of the -omics disciplines, we are witnessing fundamental changes that propel biomedical sciences toward a new level, in which the global perspectives become the fundamental priority.
-- Richard A. Stein Journal of the American Medical Association
TABLE OF CONTENTS
That Is Gene Sharing?
New Functions for Old Proteins and the Question
of Gene Duplication 2
Origin of the Term Gene Sharing"
Gene Sharing: General Definition and Implications 4
Protein Location and Gene Regulation 5
W hy the Term "Gene Sharing"? 7
Mechanisms for Diversifying Gene Functions 10
Posttranslational vlodifications 14
Conditions for Initiating Gene Sharing 14
Contrasting Phenotype with Protein Function 16
ikiRe- iHom Message 18
.- iultifunctions and Functional Shifts: Echos
'from the Past 19
Preadaptation, Prospective Adaptation, and I opeful Monsters 19
Quirky Functional Shifts and Exaptation 21
Spandrels and Gene Sharing 22
Gene Regulation and Tinkering 24
'ake-lorne Message 26
The Elusive Concept ofa "Gene" 27
The Classical Gene Concept 28
The Mendel-Morgan Chromosonmal heory of the Gene 33
Later Developments: One Gene/One Enzyme/One
Polypeptide 34
The Molecular Era of the Gene: So Much Data,
So Many Possibilities 36
Quantifying Genes before the Molecular Era 37
Quantifying Genes in the Molecular Era: Fewer than Expected 38
Noncoding Regulatory Genes 40
Protein Diversity 41
The Ambiguous Gene 46
The "Molecular Gene" Concept 48
The "Molecular Process Gene" Concept 49
The "Evolutionary Gene" Concept 49
Two Concepts for One Gene: Gene-Pi/Gene-D 5
Gene Sharing: A Concept Incorporating an "Open Gene" 52
Take-Home Message 53
4. Eyes and Lenses: Gene Sharing by Crystallins 54
Eye Diversity: Many Forms to Perform a Function 56
The Lens 59
Crystallins and the Optical Properties of the Lens 60
Diversity and Taxon-Specificity of Lens Crystallins 63
Crystallins and Gene Sharing 66
The fly-Crystallins: A Superfamnily with Distant
Stress Connections 71
The Enzyme-Crystallins of Vertebrates 75
Crystallins of Invertebrates 80
Crystalin Gene Regulation in Vertebrates: A Similar Cast
of Transcription Factors 83
Convergent Evolution of Crystallin Gene Expression 86
Evolution of Gene Sharing by shsp/aB-Crystallin 89
Convergent Evolution of Invertebrate and Vrtebrate Crystallin
Promoters 91
Potential for Lens-Specific Promoter Activity 93
Convergent Evolution and Relaxd Stringency for Crystallins 94
Take-Horme Message 95
5. The Enigmatic "Corneal Crystalins": Putative Cases
of Gene Sharing 96
The Cornea 96
Aldehyde Dehydrogenase: A Candidate Eoea C ea Cystallin 99
,Icr Candidate Corneal Crystallins: Transketolase, Isociiratc
)elwdrogenase, and Cyclophilin 101
Sceisolin: A Corneal Crystalin in Zebrafish 103
igonaling Role for C/L-Gclsoln 105
-n'alc Gene Expression 107
Rcftracton Hypothesis: Implications for Gene Sharing 109
. e n-IC Mess age 110
ne Sharing as a Common Event: Many
iutifunct onal Proteins 11
'vcoliytic Enzy mes and the Versatile Hexokinases 1 I
ira te Synthase: An Enzyme and a Cytoskeletal Stucture 114
.,te Dehicydrogenase: An Enzyme for All Seasons 115
a,ulation of mRNA Tanslation by Enzyme Binding 118
vceraldehye- 3-phosphate Dehydrogenase:
Constant Surprises 118
n lasc: Another Versatile Protein 123
atetrial Surfaice Enzymes 125
athine Oxidoreductase: Enzyme and Envelope 125
he Ih,iordoxin/Ribonucleotide Reductase System
and Thioredoxn Family Members: From Redox to
,lorphogenesis 126
umn Albumin: Transport Protein, Enzymatic Vasodilator
ncd Detoxifer 133
lsolin: Roles in Cytoskeletal Structure, Gene Expression,
Cell Death, and Signal ransduction 135
cyochrome c: Roles in Electron Transport, Cell Death,
and Light Filtration 137
lke-Homce Message 140
.- Gne Sharing during Gene Expression 141
.mplexity of Transcription 141
uclear Receptors 142
/etabolic Enzymes and Gene Expression 143
"-Box Proteins 146
anscription actors s as ranslational Regulators: Bicoid 149
anslation Factors for RNA Export: eIF4 150
Someoproteins, Chromosomal Proteins and Actin 150
T"e Dynamic Flux of Nuclear Proteins 152
ke- -iome Message 152
8. Gene Sharing As a Dynamic Evolutionary Process:
Antifreeze Proteins and Hemoglobins 1 53
Antifreeze Proteins 153
iHemoglobins 165
Take-Home Message 171
9. Gene Duplication and the Evolution of New Functions 173
Gene Duplication and Retention of Redundant Genes 174
Birth-and-Death of Duplicated Genes 176
Adaptive Evolution by Positive Selection: New Functions
after Gene Duplication 178
Subfunctionalization and Gene Sharing 181
Rapid Subfunctionalization with Slow Neofunctionalization 186
Gene Sharing Is Independent of Gene Duplication 186
Lens Crystallins: Gene Sharing at Different Stages
of Duplication 189
Take-Hom'ne Message 194
10. Gene Sharing and Systems Biology: Implications
and Speculations 195
Networks 195
Evolvability 199
Selective Pressure Affecting Gene Regulation 205
Functional Switching and the Notion of Functional
"Trespassing" 208
Functional Noise 208
Genetic Differences in Levels of Gene Expresion 210
The Molecular Clock 211
Gene Knockout Experiments 215
Gene Deletion of f-catenin 217
Horizontal Gene Transfer 219
Take-Home Message 223
11. Recapitulations: Ambiguities and Possibilities 224
Ambiguity of Cause and Effect 224
Natural Selection and Random Drift 225
Gene Sharing and Robustness: When Is a Mutation Neutral? 226
Inconsistency with Design 227
Namning Is Not Knowing 228
c Question of Tissue Hoollogy 229
Sl enctic TC rees: The Complication of Function 230
.tnii and Counting Genes 230
it: on of Polvpeptide Function: The Ambiguity
.(Molecular Mechanism 231
riC-ell Genotype and Phenotype 231
,Ce SLhring and the Importance of Research on
Drcerse Species 232
dical Implications 233
