The document summarizes the structure and function of the p53 tumor suppressor protein. It describes the various domains of p53 including the N-terminal domain, proline-rich domain, central DNA-binding domain, tetramerization domain, and C-terminal regulatory domain. It discusses how each domain contributes to p53's role in regulating genes involved in cell cycle arrest and apoptosis in response to cellular stress. The document also provides information on the location of the TP53 gene and includes figures depicting the structure and domains of the p53 protein.

1. STRUCTURE OF P53
PROTEIN
SHRUTHI .K
18308019

2. INTRODUCTION
◦ The p53 tumor suppressor protein is a classic gatekeeper of
cellular fate. It is a tumor suppressor gene and the most
frequent site of genetic alterations found in human cancer.
◦ The p53 protein is a transcription factor that regulates the
expression of a wide variety of genes involved in cell cycle
arrest and apoptosis in response to genotoxic or cellular stress.
◦ The protein was discovered because it bound to the large T-
antigen in SV40 infected cells and was therefore co-
immunoprecipitated with antibodies generated against the viral
protein.

3. CTND…
◦ p53 restricts tumor development by serving as a sensor of
cellular stress, responding to diverse signals, including DNA
damage, hypoxia, oncogene expression, nutrient deprivation,
limiting the propagation of cells under these adverse conditions.
◦ Alternatively, under conditions of low-level stress, p53 elicits
protective, pro-survival responses, such as temporary cell-cycle
arrest, DNA repair and antioxidant protein production, to
maintain genome integrity and viability in cells that sustain
limited.
◦ When an experiment was performed in cells with wild-type p53
alleles, the p53 protein disappeared with a half-life of only 20
minutes. Its located in ER, mitochondria and nucleus.

4. LOCATION OF GENE
◦ In humans, the TP53 gene is located on the short arm
of chromosome 17 (17p13.1). The MW of the protein is 53 kDa.
◦ The gene spans 20 kb, with a very long first intron of 10 kb.
◦ The coding sequence contains five regions showing a high
degree of conservation in vertebrates, predominantly in exons
2, 5, 6, 7 and 8.
(figure adapted from Proceedings of the National Academy of
Sciences of United states of America)

5. STRUCTURE OF p53
◦ Wild-type p53 protein contains 393 amino acids and is composed
of several structural and functional domains. It’s a homotetramer.
1. a N-terminus containing an amino-terminal domain (residues 1-
42).
2. A proline-rich region with multiple copies of the PXXP sequence
(residues 61-94, where X is any amino acid).
3. A central core domain (residues 102-292), and a C terminal
region (residues 301-393).
4. It contains an oligomerization domain (residues 324-355)
5. A strongly basic carboxyl terminal regulatory domain (residues
363-393)
6. A nuclear localization signal sequence and 3 nuclear export
signal sequence [18-20]

6. Figure 2: Schematic representation of p53
(Journal of Cancer Molecules , 2006)
Figure 3: p53 tumor supressor
(Protein data bank)

7. FUNCTION OF DOMAINS
◦ The N-terminus of p53 comprises two
transcriptional activation domains
(TADs), TAD1 and TAD2 . These
domains can independently enhance
transcription of p53 target genes.
◦ They are required for transactivation
activity and interact with various
transcription factors including
acetyltransferases and MDM2. PDB ID:1YCQ
Structure of the MDM2 oncoprotein
bound to the p53 tumor suppressor
transactivation domain
Kussie PH, Gorina S, Marechal V

8. Proline domain:
◦ p53 is a tumor suppressor gene which can activate or repress
transcription, as well as induce apoptosis. The human p53
proline-rich domain localized between amino acids 64 and 92 has
been reported to be necessary for efficient growth suppression.
◦ The proline-rich region plays a role in p53 stability regulated by
MDM2, wherein p53 becomes more susceptible to degradation by
MDM2 if this region is deleted.
Central DNA binding domain:
◦ The central core of this protein is made up primarily of the DNA-
binding domain required for sequence-specific DNA binding (the
consensus sequence contains two copies of the10-bp motif 5’-
PuPuPuC(A/T)-(T/A)GPyPyPy-3’, separated by 0-13 bp)
◦ It spans residues 100-300. Most cancer associated p53 mutations
are missense mutations in this domain and incapacitate DNA
binding, illuminating the key importance of DNA binding for p53-
mediated tumor suppression.

9. ◦ It is folded as a beta barrel and
exerts its function by binding as
negative transcriptional regulator.
Arg 248 in the loop of beta barrel
binds to minor groove and water
molecules in DNA. The first loop L1
binds to DNA within the major
groove.
◦ The third loop L3 packs against L1
and stabilizes it. The L2 and L3
loops are connected by a zinc atom
tetrahedrally coordinated on amino
acids Cys 176, His 179, Cys 238
and Cys 242. This zinc atom
stabilizes the structure of the loops.
Most missesnse mutations occur
here.

10. Tetramerization domain:
◦ It is a part of C terminal domain of
p53 protein present from 324-355. It
is well established that the p53
forms tetramers via an
oligomerization domain.
◦ Tetramerization appears to be
required for efficient transactivation
in vivo and for p53-mediated
suppression of growth of carcinoma
cell lines.
◦ tetramerization domain ties the four
chains together. A long flexible
region in each chain then connects
to the DNA-binding domain
PDB: 1olg- High-resolution
structure of the oligomerization
domain of p53 by
multidimensional NMR
Clore GM, Omichinski JG,
Sakaguchi

11. C-terminal basic domain:
◦ p53 contains a basic, lysine-rich domain which also functions as
a negative regulatory domain. According to the allosteric model,
in which C-terminal tail of p53 was considered as a negative
regulator and may regulate the ability of its core DNA binding
domain to lock the DNA binding domain as an latent
conformation.
◦ An interaction between the C-terminal domain and another region
in a p53 tetramer locks the tetramer in a DNA binding
incompetent state. The activation of p53 in cultured mammalian
cells has been correlated with phosphorylation and proteolytic
removal of the C-terminal domain.
◦ These modifications are thought to activate p53 by causing a
conformational change of the protein, regulated by an allosteric
effect.

12. Nuclear localization signaling:
◦ Nuclear Localization Signaling (NLS) domain, residues 316-325
have been identified in the C-terminal region. Mutagenesis of the
most N-terminal signal (NLS1, amino acids 316 ± 325) induces
the synthesis of a totally cytoplasmic p53 protein, while alteration
of the NLS2 (amino acids 369 ± 375) and NLS3 (amino acids 379
± 384) leads to both cytoplasmic and nuclear localization.
Nuclear export signal:
◦ A nuclear export signal (NES) is a short amino acid sequence of 4
hydrophobic residues in a protein that targets it for export from
the cell nucleus to the cytoplasm through the nuclear pore
complex using nuclear transport. It has the opposite effect of
a nuclear localization signal, which targets a protein located in the
cytoplasm for import to the nucleus.

13. Figure 3: Predicted protein structure of p53
Cell Death and Differentiation (1999)
PDB 1DT7: Structure of
the negative regulatory
domain of p53 bound to
S100B
Rustandi RR, Baldisseri
DM

14. REFERENCES
◦ http://asia.ensembl.org/Homo_sapiens/Location/View?r=17:7565097-
7590868
◦ Kussie, P.H., Gorina, S., Marechal, V., Elenbaas, B., Moreau, J..Levine,
A.J., Pavletich, N.P ‘Structure of the MDM2 oncoprotein bound to the
p53 tumor suppressor transactivation domain’.
◦ Venot C, Maratrat M, Dureuil C, Conseiller E, Bracco L, Debussche L.
The requirement for the p53 proline-rich functional domain for mediation
of apoptosis is correlated with specific PIG3 gene transactivation and
with transcriptional repression. The EMBO Journal. 1998;17(16):4668-
4679. doi:10.1093/emboj/17.16.4668.
◦ Bai, Ling and Wei-Guo Zhu. “p 53 : Structure , Function and Therapeutic
Applications.” (2006)
◦ May, Pierre, and Evelyne May. "Twenty years of p53 research: structural
and functional aspects of the p53 protein." Oncogene 18.53 (1999):
7621.
◦ Brady, Colleen A., and Laura D. Attardi. "p53 at a glance." J Cell
Sci 123.15 (2010): 2527-2532.

15. ◦ Harris, Curtis C. "Structure and function of the p53 tumor suppressor
gene: clues for rational cancer therapeutic strategies." JNCI: Journal of
the National Cancer Institute88.20 (1996): 1442-1455.
◦ Okorokov, Andrei L., et al. "The structure of p53 tumour suppressor
protein reveals the basis for its functional plasticity." The EMBO
Journal 25.21 (2006): 5191-5200.
◦ Arrowsmith, C. H. "Structure and function in the p53 family." Cell death
and differentiation 6.12 (1999): 1169.