P53 controls cancer in our bodies by inducing apoptosis, or programmed cell death of damaged cells. As the "guardian of the genome", p53 performs DNA repair, cell cycle arrest, and apoptosis. It is a tumor suppressor protein encoded by the TP53 gene. When DNA is damaged, p53 levels increase and it can either cause cell cycle arrest to allow for DNA repair or induce apoptosis if the DNA damage cannot be repaired. Apoptosis is controlled by the intrinsic and extrinsic pathways, which activate caspases that break down the cell into apoptotic bodies that are then phagocytosed.
2. Introduction
In 2012, an estimated 14.1 million new cases of
cancer occurred worldwide.
Out of 10 deaths 4 from cancer •
What is cancer ?
Who controls cancer in our body?
Now
3. What is cancer ?
. Cancer • Single type of cell proliferate continuously
becomes immortal further into a tumor. • Two types of tumor
Benign Tumor .
Malignant Tumor
Out of 10 deaths 4 from cancer • There are 100 different forms of
cancer. •
Most common types of cancer are lung, breast, bowel and prostate
which accounts for 4 death in 10 cancer patients •
Lung cancer is common in Men’s and Breast cancer in Female
4. Who controls cancer in our body?
P53 as a Guardian angel of the genome.
Has been described as Guardian angel of the
genome it performs flowing mechanism :
DNA repair
Cell growth arrest .
Apoptosis cell programmed cell death.
P53 is also known as cellular tumor
Antigen Ag, phosphoprotein
P53 or tumor suppressor p53.
P53 protein is encoded by TP53.
5. P53 discovering
The name p53 was given in
1979 describing the apparent
molecular mass; SDS-PAGE
analysis indicates that it is a
53-kilodalton (kDa) protein.
The actual mass of the full-
length p53 protein (p53α)
based on the sum of masses of
the amino acid residues is only
43.7 kDa
6. Overview
DNA damage Trigger expression of P53
gene
Increased P53
levels
Prevent cell
form entering
S phase of
cell cycle
Arrest of cell cycle
at G1 phase
Allow time for the DNA repair
to take place
P53 Induces
DNA repair gene DNA not repair
ApoptosisPermanent
arrest
senescence
DNA repaired
P53 degrades
Cell cycle continue Conserve
stability
Gradient of
genome
7. What is : P53
(phosphoprotein p53)
This difference is due to the high number of proline residues in the protein,
which slow its migration on SDS-PAGE, thus making it appear heavier than it
actually is.
The human TP53 gene encodes at least 15 protein isoforms, ranging in size
from 3.5 to 43.7 kDa. All these p53 proteins are called the p53 isoforms.
8. P53 roles
transformation-related protein 53 (TRP53), is any isoform of a
protein encoded by homologous genes in various organisms,
such as TP53 (humans) and Trp53 (mice).
This homolog (originally thought to be, and often spoken of as,
a single protein) is crucial in multicellular organisms, where it
prevents cancer formation, thus, functions as a tumor
suppressor.
p53 has been described as "the guardian of the genome"
because of its role in conserving stability by preventing
genome mutation.
9. The TP53 gene is the most frequently mutated gene (>50%) in human
cancer, indicating that the TP53 gene plays a crucial role in preventing
cancer formation.
TP53 gene encodes proteins that bind to DNA and regulate gene
expression to prevent mutations of the genome.
11. Protein 53 structure
TP53 gene is located on the short arm of chromosome 17 (17p13.1) •
he p53 protein is active as a tetramer of 4 chains of 393 amino acids. Each
chain has several domains.
At the N-terminal there are two distinct transactivation domains (TADI and
TADII), a nuclear export signal (NES) followed by the proline rich domain (PD)
and the DNA binding domain (DBD).
12. Then at the C-terminus there is an oligomerization domain (OD),
three nuclear localization signals (NLS), a second NES and a
lysine rich regulatory domain (RD).
The TADI (residues 1-42) and TADII (residues 43-62) are critical
for p53’s regulation since they provide binding sites for the
transcriptional machinery and the negative regulator MDM2 - they
are differentially involved in the activation of a distinct set of p53
target genes.
13. The exact function of the PD (residues 63-97) is not well understood
but the high proline frequency is conserved though species.
Additionally, from research using mouse models it is also known that
the length of the PD is critical to maintain p53’s tumor suppressive
function, and the domain also contains a common single nucleotide
polymorphism (SNP) at codon 72 again highlighting the
significance of this region.
14. The DBD (residues 102-292) is pivotal for the transcriptional activity of p53.
It contains 4 of the 5 conserved boxes in p53. The OD (residues 323-356)
allows p53 to form a tetramer which is organized as a dimer of dimers.
The C-terminus of p53 contains a cluster of three NLSs that mediate the
nuclear location of the protein. These sequences bind to specific receptors
and allow selective passage of p53 through the nuclear pore complex.
The C-terminal NES, a highly conserved region has been shown to be
essential for nuclear export of p53. Both the NLS and NES regions are
required for nuclear-cytosolic shuttling of p53 as a means to regulate p53
transcriptional function
15.
16. Apoptosis
introduction
Cell death is part of normal development and maturation cycle, and
is the component of many response patterns of living tissues to
xenobiotic agents (i.e. micro organisms and chemicals) and to
endogenous modulations, such as inflammation and disturbed
blood supply.
17. Cell death is an important variable in
cancer development, cancer
prevention and cancer therapy.
In the treatment of cancer, the major
approach is the removal, by surgery,
of the neoplasm and/or the induction
of cell death in neoplastic cells by
radiation, toxic chemicals, antibodies
and/or cells of the immune system
18. On the other hand, this path biological process remains poorly
understood and the physiological and biochemical factors that
lead to cell death are still not clear.
19. One main factor is the existing confusion between ‘apoptosis’
process, as compared and contrasted with ‘necrosis’, leading to the
overlapping of the ante mortem changes, i.e. the process of cell
death, and the post-mortem changes, i.e. the necrosis process.
What is Apoptosis
20. Apoptosis, also known as programmed cell death, is
characterized by specific morphological and biochemical changes.
In most cases, physiological cell death occurs by apoptosis as
opposed to necrosis.
The term ‘apoptosis’, defined as a controlled type of cell death
that can be induced by a variety of physiologic and
pharmacological agents.
Apoptosis is controlled by
What is Apoptosis
Intrinsic pathway
extrinsic pathway
caspases
22. Apoptosis
On the basis of the following main morphological criteria:
cellular shrinkage, condensation and margination of the
nuclear chromatin, DNA fragmentation, cytoplasmic
vacuolation, cell lysis.
23. Apoptosis
mechanisms
Apoptosis : before cell’s destruction,
cell must be given its orders):
Apoptosis : in three steps.
1) initiation by two different
mechanisms, depending whether
the initiate signal come from
outside or from inside the cell
2) Execution.
3) Phagocytosis.
24. Apoptosis Mechanisms
Intrinsic pathway. The mitochondria in the cell keep it
alive by aerobic breathing (providing oxygen to the
cells).
extrinsic pathway activation mechanism is when
receptors bind within the cell and open up the
mitochondrial pores.
When this happens, it causes a balance of pro-apoptoic
proteins and anti-apoptotic proteins, allowing the
process to activate. Lead to activation of Execution
is caspases
25. extrinsic pathway
Death Receptors- cell surface
receptor that transmit apoptotic
signals, initiated by ligands
Ligands: Fas ligand, Tumor
Necrosis Factor (TNF) alpha,
and Tumor necrosis (TNF)-
related apoptosis-inducing
ligand TRAIL.
Lead to generation of ceramide
Result in large number of
clustering of death receptors.
26. Death domain. Conformation
change in the intracellular domain
of the receptor.
Allows recruitment of various
apoptotic proteins to the receptor.
Final step- recruitment of caspase
8.
Resulting the activation of
caspase 8 and the initiation of
apoptosis.
27. Apoptosis mitochondria
pathway
1. Apoptotic proteins cause
mitochondria to swell up,
opening their pores.( in the
cytosol of cell it contains
proteins which stop apoptosis
from happening)
2. mitochondria pores open
up: they release mitochondrial
proteins which bind with
these other proteins. Mit.
Protein is known SMACs
28. Mitochondria contains proteins like Apoptosis Inducing Factor (AIF),
Smac/ DIABLO and Cytochrome C that regulate cell death.
These proteins are release through the a pore called Permeability
Transition (PT) pore.
The release of Cytochrome leads to recruitment of pro-caspase 9 and
Apoptotic protease activating factor 1 ( Apaf-1). This forms the
apoptosome.
Intrinsic pathway of apoptosis
32. Mechanism (Intrinsic) cont.
This is follow by the activation of caspase 9 which in turn result with
the induction of apoptosis.
Most Important player
ProteasesAspartate –directionCysteine– dependent
Caspases
Caspases : are a family of protease enzymes playing essential
roles in programmed cell death and inflammation:
34. All types of ( initiator and executioner) caspases are in
inactive form , these are called procaspases.
The initiator caspases are activated by extrinsic
pathway and intrinsic pathway.
The executioner caspases are activated by intrinsic
pathway.
35. Caspases
1. After forming a complex between
Death Domain & Fas Associated
Death Domain, the.
procaspases8 will activate
Activated caspase 8
Activated caspase 3,6& 7
36. Nuclear breakdown by endonuclease activation & breakdown
cytoskeleton. After that formed apoptotic body have receptors to
macrophage lead to phagocytosis
