Molecular Biology
Department of Molecular Biology and Pharmaceutical Biotechnology
(45-308)
Mgr. Marie Brázdová, Ph.D. (FAF, BFU AVČR)
RNDr. Jan Hošek Ph.D. (FAF)
Mgr. Daniel Renčiuk, Ph.D., (BFU AVČR)
brazdovam@vfu.cz,
MB_1_2017 1
examination requirements:
• Exam has both written and oral part
• Test: min 60% to pass (E), ….90-95% (A)
Moodle- molecular biology 2016
MB_1_2017 2
Suggested literature
MB_1_2017 3
outline of the first lecture
• defining molecular biology
• historical context
• living systems: types, properties
• prokaryotic x eukaryotic cells
• cell-free systems
• model systems in molecular biology
MB_1_2017 4
What is molecular biology?
• field studying relationships between physical structure,
mutual interactions of biomolecules and the properties of
living systems
• explores relationships between two levels of living
systems: between physical/chemical (structure and
function of biomacromolecules) and biological (properties
and functions of cells/organisms
MB_1_2017 5
Molecular biology x Biochemistry
• biomolecular interactions, mainly information biomacromolecules,
the functions and properties of living systems.
• The goal of molecular biology is to explain the functions and
features of living systems and the relationships in between the
structure and interactions of their molecules (macromolecules).
• These relationships are explained from a complex point of view
integrating physical, chemical and biological methods.
• Studies processes that take place in living systems at the molecular
level and in which genetic information is processed
• Biochemistry
• Biochemistry addresses chemical processes in living organisms. The
field of study in biochemistry is the structure and function of the
basic building blocks of living matter like sugars, fats, proteins,
nucleic acids and other biomolecules.
MB_1_2017 6
Principles of Molecular Biology are
making their way into all biology fields
• originally focused on heredity – maintenance and
expression of genetic information and its inheritance
(molecular genetics)
• currently concerned with common characteristics of life
at the molecular level, which are valid across the outer
diversity of living creatures and the essence of
processes taking place in cells and organisms
• practical applications: biotechnology, paleontology,
archeology, evolution, medicine, anthropology,
criminalistics, determining parenthood, etc.
MB_1_2017 7
Importance of molecular biology
• research moves to a level that is common to all living
systems
• Enables cellular manipulations– affect their characteristics
in desired the direction (human and veterinary medicine,
biotechnology, gene engineering, agriculture, etc.)
• Brings in new possibilities to study phylogenetics,
evolution, etc.
• Molecular biology belongs along with information technology
to the most progressive fields of present times
MB_1_2017 8
Historical background
• Crossbreeding of plants and animals
is done for thousand of years, yet
genetics as a science arose only in
the 80s of the 19th century
• Techniques for investigating the
associations between genes and
observable traits are available only a
few decades
• The era of DNA cloning and
executing targeted alterations to
genetic information began in 70s of
the 20th century (Stanford
University, UCSF, Genentech) –
biotechnology used to prepare drugs
MB_1_2017 9
• Gathering information about molecules of life dramatically
speeded up in the last several years
• milestones: DNA double-helix discovery, central dogma of
molecular biology, restriction endonucleases, gene cloning,
reverse transcription, DNA sequencing,h PCR, monoclonal
antibodies, microarrays, RNA interference, stem cells,
artificial nucleases, etc…
MB_1_2017 10
MB_1_2017 11
Important milestones in molecular biology
• 1944 – purified DNA used to transform bacteria
• 1953 – model of DNA structure (J. Watson, F. Crick, M. Wilkins)
• 1956 – genetic information is written in DNA as a sequence of bases
• 1958 – complementary DNA strands separate during replication
• 1958 – isolation of DNA-polymeraseI and DNA synthesis in vitro
• 1958 – postulating central dogma of molecular biology
• 1960 – discovering mRNA and prooving its function
• 1961 – mRNA used to decipher genetic code
• 1961 – experimental evidence to central dogma of MB
• 1961 – operon theory postulation – regulation of gene expression
• 1966 – complete deciphering of genetic code
• 1970 – first restriction enzyme was isolated
• 1970 – reverse transcriptase discovered in retroviruses
• 1972 – first recombinant DNA molecules prepared in vitro
• 1973 – beginnings of gene clonning – GI basis
The central dogma of molecular biology
• genetic information is passed by transfer of the DNA into RNA
and protein (this postulate is called the central dogma of MB)
• In some viruses (e.g. HIV), RNA is used as a template for DNA
synthesis by reverse transcription
• many genes encode a polypeptide, however RNA molecules in the
cell play important roles
Reverse
transcription
TEST
1958 – postulating central dogma of molecular biology
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MB_1_2017 13
TEST
MB_1_2017 14
Important milestones in molecular biology
• 1975 – Asilomar conference – moratorium on work with recombinant DNA
• 1977 – first recombinant molecules to carry mammal genes
• 1977 – discovery of composed genes – exons/introns – pre-mRNA splicing
• 1977 – introducing DNA sequenation
• 1981 – discovery of RNA catalytic activity – ribosomes
• 1982 – human insulin produced commercially inside bacteria
• 1983 – bacteriophage λ - whole DNA sequence acquired
-starting projects to sequence genomes of model organisms
Genomic and postgenomic era
• analysing genome sequences
• genome x proteome
• bioinformatic approach
Present
• Since 2003 we have access to DNA nucleotide
sequence that constitutes the human genome
(approximately 20.000 genes, 23 chromosome
pairs, 3x10 9 base pairs/haploid cell)
• We thus have the information necessary for the
establishment and functioning of human beings
• only 1,5% of the human genome consists of genes
encoding the proteins, the rest consists of areas
coding RNA, regulatory sequences, introns
• The functions of many human genes are not
sufficiently explored, even less is known about
non-coding sequences
MB_1_2017 15TEST
Present - challenges
understanding of the mechanisms coordinating gene expression and
their relationship to human health (all diseases have hereditary
component that gets co-decided by genes)
Curing hereditary diseases: resulting from faulty gene function
carried over from parents to offspring – to understand the cause
we must first understand the function of healthy genes
Cancer treatment: also a consequence of gene dysfunctions,
search for early diagnosis markers and appropriate targets for
gene therapy, search for new chemotherapeutic agents
Gene engineering and biotechnologies in agriculture: food source
improvement (resistance to external adversities)
MB_1_2017 16TEST
MB_1_2017 17
What is life?
satisfactory definition does not exist
Generally accepted characteristics of living organisms:
highly organised
composed of one or more cells
contain their own plan of arrangement, ie. the genetic program
(genotype)
acquire and use energy
implement and control many chemical reactions
 grow and change their appearance and abilities (ie. phenotype)
 keep a relatively constant internal environment
 reproduce
 respond to changes in the environment
They may evolve over time
TEST
MB_1_2017 18
What is life?
 a key feature is the ability to reproduce. That is
replicating the genetic information (genome), and the
structure that is its bearer and protector (cell).
 growth and reproduction requires information and energy
 energy is one of the products of metabolism
Metabolism is a set of processes, by which are nutrient
molecules transmitted and converted so that the cells are
provided with energy and new building materials
MB_1_2017 19
Living organisms evolve
 life on earth is changing by a process of evolution
organisms which are identical or very similar to parental
organisms arise by reproduction
 but genetic information in progeny/offspring generations
gradually accumulates changes
 accumulation of changes is related to the properties of
molecules of nucleic acids and external environment
 a essential feature of life is that it presents a dynamic
balance between its precise duplication and tolerance to
changes
Terminology
Genetic information: biological information written in nucleic
acid (DNA or RNA) oligonucleotide sequence
gene: unit of genetic information determining protein/RNA
structure (physically: nucleic acid segment)
DNA: serves long term genetic information storage
RNA: is involved in mechanism by which genetic information is
put into practical use
MB_1_2017 20TEST
genome: the sum of all the genetic material of an organism,
cell or organelle, which copy is transmited to offspring (genes;
non-coding sequences are included as well)
genotype: genetic constitution of an organism represented by
a set of alleles of its genome (relative to individuals of that
specie)
• phenotype: the sum of characteristics, genotype manifestation
in the environment
• metabolism: a set of processes for energy and building the
substances necessary for the biosynthesis of cellular
components; term growth, reproduction and realization of
genetic information
ribosomes: key components in cell apparatus, create cellular
proteins according to gene instructions
MB_1_2017 21TEST
Terminology
Living organisms are made up by cells
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• variability of the manifestations of life versus the unity of
their foundations
• cellular structure based on similar ingredients occurs at all
life forms
• Schleiden and Schwann in 30s of the 19th century: cells are
the building blocks of life
1. All living organisms are composed of
one or more cells.
2. The cell is the basic unit of structure
and organization in organisms.
3. Cells arise from pre-existing cells.
Cells can differ substantially from
each other…
• variability in size and shape…
• can live freely or be tied to
a matrix or other cells
MB_1_2017 23TEST
…still they have much in common
• Are separated from the outer world by plasma membrane
(with characteristic phospholipid structure)
• Plasma membrane systems control import into the cell
and export from the cell
• Cellular structures are build up from food molecules
processed by cells own systems using energy
• Contain genetic material carrying information needed to
create/restock all cell components
• Dispose of system for gene expression through which
genetic information is conveyed into practical use
• Particular proteins or RNAs (defined by genes) can form
structures of higher order
MB_1_2017 24
Minimal requirements for the
existence of a living cell
• Plasma membrane (to separate cell
from outer environment)
• Ability to build up cellular structures
from simple molecules via utilizing
external energy sources
• Presence of genetic information
defining cell characteristics
• Presence of system to express genetic
information
MB_1_2017 25TEST
MB_1_2017 26
Unicellular organisms
• the simplest organisms
• they live as separate units
• reproduce
• successfully adapt to extreme conditions (high / low
temperature, aerobic / anaerobic, etc.).
• often live inside other organisms
MB_1_2017 27
Multicellular organisms
• cells specialize in certain functions - differentiate, that is changing
gene expression in different cells of the same
organism, leads to their phenotypic diversification
• some cells maintain the undifferentiated state (stem cells)
• significant structural and functional specialization of cells,
leads to division of labor inside the body (often accompanied
by a loss of ability growth and division)
• cells communicate with each other to ensure proper function
of the whole organism
MB_1_2017 28
Plasma membrane - function
• ensures cell autonomy (cellular components exist in a
limited space)
• ensures that the aqueous medium within the cell
differs from the outer medium
• contains protein complexes that control import and
export of molecules through the membrane
• transmits signals between the external and internal cell
environment
MB_1_2017 29
Plasma membrane - structure
• two-layer unit composed of phospholipids and proteins
Phospholipids
- Contain a water soluble head, which
includes phosphate, exposed towards
inner and outer membrane surface; and
a hydrophobic part (a pair of fatty
acid chains), which form membrane
body
Molecules that carry both hydrophobic
and hydrophilic area called amphipathic
MB_1_2017 30
Plasma membrane - structure
• aquatic environment inside and outside the cells
results in aggregation of hydrophobic lipid strings
(forming the inner environment of the membrane),
hydrophilic (charged phosphate) heads form the outer
surfaces of the membrane
• lipid bilayer membrane allows for merging membranes
and creates suitable environment for binding proteins
MB_1_2017 31
Plasma membrane - permeability
• membrane is not freely permeable to ions, small charged
(hydrophilic) molecules and large molecules
• water molecules and hydrophobic molecules can pass through
the membrane
• different ion concentrations on both sides of the membrane
may create osmotic pressure (the movement of water
molecules through the membrane towards the environment with
a higher concentration of ions)
• risk of cell damage
MB_1_2017 32
Cells manage their content
• intracellular pH and ion content are subjected to tight
regulation
• specialised membrane transporters help to achieve
required balance
• metabolism substrates (energy sources) must also pass
through plasma membrane, as well as basic components
of cellular structures
• unwanted metabolic products or ions must be exported
through the membrane
• both directions have a high transport selectivity
• the ability of cells to maintain stable internal
environment is called homeostasis
Protein channels control ion passage
through plasma membrane
MB_1_2017 33
•create a channel in lipid bilayer
•the outer surface of protein channel is in contact with
membrane lipids
• inner surface is surrounded by aqueous medium
• ions and hydrophilic molecules pass through the channel
without getting into contact with membrane lipids
Ion channels and protein carriers
• Two mechanisms to transfer ions across membrane:
according to gradient direction or against the gradient
• Ion channels are used to transport ions (without energy
requirements) from places with higher ion concentration to
places with lower ion concentration (in gradient direction)
• Protein carriers transport ions against electrochemical
gradient, which requires energy
MB_1_2017 34
TEST
Controlling ion channels
• Cannot be open all the time (ion concentrations would be
equalized)
• Open up by undertaking a conformational shift
• conformational shift can be induced by various stimuli
(signal molecule, electric voltage, temperature)
MB_1_2017 35TEST
Cell membrane is not a firm/hard
structure
• But a weak, flexible
and fragile one
• Mechanic support is
often provided by cell
wall, placed outside
cell membrane, common
in bacterial and plant
cells
• Animal cells are
supported by
cytoskeleton
components
MB_1_2017 36
Two types of living cells
• Classification by internal division, compartmentalization
(compartment = membrane enclosed space)
• prokaryotic cell: simpler, consists of only one
compartment with the genetic material, apparatus, and
products of gene expression
• eukaryotic cell: complex, comprising at least two
compartments, one of which contains the genetic
material
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TEST
MB_1_2017 38
Prokaryotes
• Unicellular organisms
• cells are surrounded by a
membrane
• membrane surrounded by a cell
wall providing protection
• DNA located in the cytoplasm
• it includes all chemical and
structural components
necessary for life
• all the genetic information
present on one chromosome
TEST
Two types of prokaryotes:
bacteria and archaea
• phylogenetic relationship of these groups was determined
relatively recently modern methods
(particularly DNA sequencing): archaea are a separate group
of prokaryotes
• archaea have the appearance and structure similar to bacteria:
Small single-celled organisms without internal membranes
• they live in extreme conditions (high temperatures, acidity, salt
content)
• archaea often use unusual metabolic pathways, show
chemical differences in the construction of cell walls, have an
apparatus for gene expression, which is more like in eukaryotes
than bacteria
MB_1_2017 39
The genetic material of prokaryotes
• the simplest genome are present in bacteria that live freely
but within other organisms (Mycoplasma)
• Host provides compounds which bacteria need, but cannot
create
• their genome contains only about 500 genes that encode a
basic structural cellular components
• genome of bacteria comprises at least 1500 genes that
encode the structural elements in addition to enzymes and
also more advanced system for gene expression regulation
MB_1_2017 40TEST
classification of bacteria
2 groups that diverged about 2 billion
years ago:
• Gram-negative (e.g. E. coli) and
Gram-positive (e.g. B. subtitlis)
•depending on how they react with
Gram stain
•sensitivity given by dye interaction
with the cell wall
MB_1_2017 41
Gram staining
G+ bacteria have plasma membrane surrounded by a cell wall
formed by proteoglycans and polysaccharides (blue / violet color)
Gram-negative bacteria have the outside wall surrounded by
lipopolysaccharide layer (red / pink color)
MB_1_2017 42
Bacteria - a model for research of
basic cellular processes
• advantages:
• unicellular microorganisms, uniformity of response to
external stimuli
• low number of genes
• haploid state (only one copy of each gene)
• possibility of culturing under strictly controlled
conditions (defined precisely by medium with the content
of salts and carbon source)
• high growth rate, doubling time is only 20 minutes
• the possibility of storage in cold boxes (-70 °C) for 20
or more years
MB_1_2017 43
Model bacterium - Escherichia coli
• rod-shaped bacteria (size 1 x 2.5 micron)
• the natural environment of the intestine (colonbecause
"coli")
• belongs among Gram-negative bacteria
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Where can we find bacteria in nature?
• Almost everywhere (60 km high in the atmosphere, 11
km below sea level, in both fresh and salt water or
sewage, soil, plant roots or in bodies of animals)
• the number of bacteria on earth is huge (amounts of
bacterial carbon on Earth corresponds to the amount of
carbon in plants)
• the bacteria is likely to constitute more than half of live
mass of Earth
MB_1_2017 45
Prokaryotes are very adaptable
• their lifestyle is varied and can adapt to extreme conditions
(pH, presence of oxygen, temperature, etc.).
• Classification according to the ability to grow at different
temperatures:
• mesophilic: grow best between 25 and 40 of °C (this
includes the human pathogens)
• psychrophilic: grow best between 15 and 20 °C (but there
are also those that live at 0 °C) - a favorite environment cold
water and land
• thermophilic: grow best between 50 and 60 °C (some
tolerate even 110 °C)
MB_1_2017 46
Bacteria are sensitive to natural substances
• Various bacteria in the same environment compete for resources
• excretion of toxic proteins, e.g. bacteriocins - kill related
bacteria, but no strains - producers (utilization of bacteriocin
plasmids as vectors)
• Creation of antibiotics (clinical use)
MB_1_2017 47
Some bacteria are harmful, others
are useful
• a small portion of pathogenic bacteria: the originator of
infectious diseases (cholera, tuberculosis, anthrax, syphilis,
gonorrhea, whooping cough, diphtheria, etc.), what
contributes to the eradication: sanitation, clean water, soap,
flush toilets, as well as vaccinations and antibiotics
• Most bacteria have a positive meaning: it contributes to the
balance of ecosystem (decomposition of dead bodies of
plants and animals)
• destruction of waste products of human activity and
pollution
• higher life forms could not survive without bacteria
MB_1_2017 48TEST
Eukaryotic cell contains several
compartments
• increasing the complexity of the cell - the division of labor at the
cellular level, interior space is divided into two main sections sealed
by membrane: cytoplasm and nucleus
• macromolecules are transported into and from the nucleus via the
nuclear pores (protein channels)
• pores are fully permeable to smaller molecules, i.e. the aqueous
environment of the nucleus does not differ from the cytoplasm
MB_1_2017 49
Genetic material is located in the
nucleus
• unlike prokaryotes eukaryotes genome must ensure
specification of new structural elements, define the location
of proteins into the correct sections, use a more complex
mechanism of gene regulation
• Genetic complexity of eukaryotes:
the simplest single-celled organisms
eukaryotes carry about 5,000 genes, human
about 20000 genes encoding proteins
MB_1_2017 50TEST
Eukaryotic cell
contains additonal
organelles
• surrounded by membranes with
the same structural features as the plasma membrane
• cytoplasmic = organelles + cytosol
• cytosol is an aqueous environment of the cytoplasm,
where proteins are synthesized, which remain either in
the cytosol or are transported to any organelle or
outside of the cell
• organelle membranes are permeable, so the inner
organelles environment differs from the cytosol (the
exception is nucleus with its pores)
MB_1_2017 51
Eukaryotic cell contains additonal
organelles
• endoplasmic reticulum - protein folding, assembling
oligomers , (ribosomes-translation)
• Golgi apparatus - secretion of proteins and other
material outside the cell
• lysosomes - containing digestive enzymes – decay of
molecules
• mitochondria - size, shape, containing circular DNA,
resemble bacteria - a specialist in energy recovery -
respiration
• chloroplasts - specialized for photosynthesis, contain
chlorophyll and other molecules necessary for capturing
light, containing circular DNA like mitochondria
MB_1_2017 52TEST
The diversity of eukaryotes
• Unlike two genetically distinctive branches of
prokaryotes, all eukaryotic organisms are genetically
related
• originate from a common ancestor
• unicellular eukaryotes: yeast, protozoa
• multicellular eukaryotes: plants, fungi and animals
MB_1_2017 53
Two main cell types of eukaryotes
•somatic cells and gametes
•in most multicellular organisms, cells are
specialized into tissues and organs
•Gametes are part of the reproductive system and
participate in the formation of the next
generation
•somatic cells form the body, creating good
conditions for the functioning of the gametes, do
not participate in reproduction
MB_1_2017 54
Model organisms
• For practical reasons they are preferred in research
• It assumes that the gained knowledge will apply in the
other organisms, at least for those related to model
organisms
• it is not always true for human medicine or agriculture
that we should examine directly target organisms
MB_1_2017 55
Yeast - model unicellular eukaryotes
• unicellular eukaryote - similar benefits as bacteria
• genome was sequenced first (in eukaryotes) - in 1996
• belong among fungi - similar to animals and plants
• alternation of diploid and haploid phase, you can work with
haploid cultures, which facilitates genetic analysis
• haploid genome contains only about 6,000 genes
MB_1_2017 56
Yeast
• only few genes (about 5%) contain introns
• They grow in a chemically defined medium, forming
colonies on agar plates
• the generation time of approximately 90 minutes
• the ability to easily preserve in frozen state
• specific multiplication by budding
• model is suitable for studying the function of genes and
cell cycle
MB_1_2017 57
Nematodes
• Caenorhabditis elegans
• non-pathogenic soil nematodes
• genome has a 7x higher DNA content than yeast
• higher content of introns and non-coding sequences
• 1 mm body composed of 959 cells
• evolution of each one from the original zygote is
described
• model for studying development, apoptosis, aging
• RNA interference was first described in this model
MB_1_2017 58
Flies
• Drosophila melanogaster:
• life cycle of two weeks
• 14 000 genes
• research on cell differentiation,
development of an organism, cell signaling
and behavior
MB_1_2017 59
Zebrafish - a model for the study of
evolution of vertebrates
• Zebrafish/Danio rerio: small freshwater
fish (2,5 cm)
• fertilized egg develops outside the womb - can be monitored
by microscopy
• Development from egg to adult organism takes 3 months,
thanks to the transparency we can follow the development
of internal organs
• Easy microinjection of foreign DNA into the egg
• Molecular genetics of development
• 25 chromosomes, 75% homology with the human genome
MB_1_2017 60
Mouse
• model organism for humans
• lives 1-3 years, reaching sexual maturity after 4
weeks
• contains a 20 chromosome pairs
• less than 1% of mouse genes does not have a
human homolog
• used to study gene function
MB_1_2017 61
Human
• for ethical reasons we can not experiment with people
• it is possible to cultivate human or animal cells in
culture
• immortal cell lines (e.g. HeLa cells) are formed by
tumor cells
• HeLa cells are tumor cells derived from cervical
cancer of Henrietta Lacks in 1951
• cell line is a suitable model for molecular biology
studies
MB_1_2017 62
Arabidopsis – model for plants
• molecular biology of plant has historically been
somewhat lagging behind other organisms
• often they have many genes (rice: 40 000 to 50 000
genes)
• reason: they can not protect themselves by
movement, thus accumulate genes for protection and
adaptation
• the challenge now: genetic improvement of crops
• Arabidopsis thaliana: structural simplicity, small
genome, five pairs of chromosomes and about 25,000
genes
• maturing plants to produce seeds takes 6 to 10 weeks
• can be cultivated in the haploid state - advantage for
genetic analysis
MB_1_2017 63
Virus
• does not have the cell structure
• contain their own genes wrapped in a protein coat,
but it can not express them
• lacks apparatus which ensures the cells energy
• cellular parasite, replication and expression of viral
genes is carried out by infected cell
• viral genetic information is stored in the DNA or RNA
• he is able to cause disease
• applies in genetic engineering
MB_1_2017 64
Bacterial virus = bacteriophage
• infects a bacterial cell that is caused to produce new
bacteriophages, eventually bursts, releasing a new
generation of bacteriophages
• each of the new virions can infect additional bacteria
• within a few hours phage epidemic can destroy bacteria
cultures of the number exceeding several human
population
MB_1_2017 65
Human viruses
• infects human cells, originator of common diseases (measles,
mumps, chickenpox, colds and flu) and serious diseases (polio,
Ebola, AIDS)
• Infection of less dangerous virus may provide resistance
against much more dangerous virus
• viral infection can not be cured; necessary prevention –
immunization
• can transfer genes from one organism to another host
(importance for evolution and genetic engineering)
• Antibiotics have no sense in fighting viral infections, can only
help with parallel bacterial infection
MB_1_2017 66
Other genetic elements
• are widespread in the biosphere
• various functions: they can cause serious illness or existence is
almost unnoticeable
• They carry genetic information, but do not have tools for the
life functions, do not exist outside the host cell
•Viruses are one of the most advanced
• viroids and plasmids: autonomous nucleic acid
molecules that do not have protein shell
• viroids are RNA molecules that infect plants and force them to
produce new viroids released into the environment
MB_1_2017 67
Other genetic elements
•plasmids
• DNA molecules that are stably maintained within the
host cell
• They may pass from one cell to another only if between
them there is contact
• do not kill the host cell
• widely used in genetic engineering
MB_1_2017 68
Other genetic elements
•transposable elements (transposons)
• DNA molecules that do not replicate as separate
units
• for its replication they require incorporation into
other DNA molecules that have self replication
ability
• have the ability to jump from one host DNA to
another
MB_1_2017 69
Other genetic elements
•prions
• infectious protein molecules
• they contain no nucleic acid
• infect cells of the nervous system of animals and cause serious
illness (eg. mad cow disease)
• represent incorrectly folded version of the normal protein of
the nerve cells
• if they penetrate into the cell they cause incorrect folding of
the corresponding normal protein which kills the cell
MB_1_2017 70
The central dogma of molecular biology
• genetic information is passed by transfer of the DNA into RNA
and protein (this postulate is called the central dogma of MB)
• In some viruses (e.g. HIV), RNA is used as a template for DNA
synthesis by reverse transcription
• many genes encode a polypeptide, however RNA molecules in the
cell play important roles
Reverse
transcription
TEST MB_1_2017 71
72
p53 tumor suppressor and p53 binding to
human genome
- maintaining genomic stability
- transcription-dependent tumor suppressi
Bieging and
Attardi, Trends in
Cell Biology
(2012)
How does p53 select its targets?
- in response to various inputs, the p53
protein becomes stabilized
- upon stabilization of p53, various
transcriptional outputs determined by:
- the strength of the p53 RE
- posttranslational modification status of
p53
- specific p53 binding partners
- the epigenetic landscape of target gene
promoter
- conformation of DNA, non-B DNA
structures
MB_1_2017
Selected oncogenic properties of mutant p53 and their underlying
mechanisms
Ran Brosh & Varda Rotter
Nature Reviews Cancer 9, 701-713 (2009)
MAR/SAR elements in DNA (mutp53CD, C-terminus) (Muller
et al., 1996; Deppert et al., 2000)
Structure/sequence motifs in DNA
73MB_1_2017
Transactivation Sequence-specific DNA binding
3´- 5´ Exonuclease
Oligomerization
50 150 200 250 300 350 393100
N CI II III IV V
NLS
C-terminal DNA binding
PuPuPuC(A/T)(T/A)GPyPyPy
Mutation of TP53
R175
G245
R249
R248
R273
R282
175
245
248
273
282
Cho et al. 1994
A point mutation in
TP53 leads to loss of
p53 tumor suppressive
function
74MB_1_2017